Beneficial effects of administering intraportal prostaglandin E1 postoperatively to hepatectomy patients with massive intraoperative blood loss

Massive intraoperative blood loss is a major cause of complications following hepatectomy. To evaluate the efficacy of intraportal prostaglandin E₁ (PGE₁) for preventing liver deterioration in hepatectomy patients with an intraoperative blood loss of over 2000 ml, a retrospective analysis was conducted on 10 patients given intraportal PGE₁ (portal group), 6 given intravenous PGE₁ (venous group), and 10 given no treatment (control group). PGE₁ was infused at 250 or 500 g/day in the portal group and at 720 g/day in the venous group, and continued for 3 days postoperatively. Alanine aminotransferase (ALT) and total bilirubin (T.Bil) were measured on postoperative days (PODs) 1, 3, 5, and 7. ALT was lower in the portal group than in the other two groups on each POD, and significantly lower than in the control group on POD 3 (P<0.05). T.Bil was significantly lower in the portal group than in the control group on PODs 5 and 7 (P<0.05). T.Bil on POD 7 was under 1.5 mg/dl in 1 (10.0%), 6 (60.0%), and 2 (33.3%) of the control, portal, and venous group patients, respectively, with a significant difference between the control and portal groups (P<0.05). These results confirmed that intraportal PGE₁ was beneficial for improving hepatic function and preventing cholestasis in patients with a blood loss of over 2000 ml at risk of developing postoperative liver deterioration.     

The effects of intraportal administration of prostaglandin E1 on liver ischemia and hepatectomy in rats

The effects of intraportal administration of prostaglandin E₁ (PGE₁) on portal venous flow, hepatic arterial flow, peripheral tissue blood flow, and systemic arterial flow before and after 60 min total liver ischemia followed by 70% partial hepatectomy in rats were investigated. Total liver ischemia was induced by occluding the hepatoduodenal ligament for 60 min. PGE₁ at a dose of 0.5 μg/kg/min was infused intraportally for 15 min before inducing hepatic ischemia (preischemic period) and for 60 min after ischemia (postischemic reperfusion period) in the treatment group. Normal saline was infused in the control group. Seventy percent partial hepatectomy was performed during ischemia. Serum biochemical analysis and liver tissue histology were carried out 1, 3, and 24 h, and 1 and 24 h after reperfusion respectively. One-week survival of the PGE₁ group was improved to 70% compared to that of the control group of 30%. Postischemia reperfusion values of portal and peripheral tissue blood flows in the PGE₁ group were 6.33 ± 0.600 ml/min and 27.2 ± 23.5 (arbitrary), and were significantly different from those of the control group of 4.34 ± 0.400 ml/min and 23.5 ± 5.54 (arbitrary), respectively. There was no significant difference in hepatic arterial flow between the two groups. Serum alkaline phosphatase decreased significantly in the prostaglandin group. Histological examination revealed a significant portal venous congestion in the control group 1 and 24 h after reperfusion. The extent of the sinusoidal congestion was also severe in the control group 24 h after reperfusion. It was concluded that PGE₁ has a protective effect against liver damage when the liver was injured by warm ischemia and reperfusion followed by partial resection. Received for publication on May 30, 1997; accepted on July 27, 1998     

The mechanism of hepatic graft protection against reperfusion injury by prostaglandin E1

1 (PGE₁) on protecting against hepatic endothelial cell damage and increasing graft viability after cold preservation and reperfusion, using an isolated perfused rat liver (IPRL) model. The grafts were divided into three groups, according to the cold preservation time and PGE₁ administration, namely: 4 h preservation (group 1, n = 9), 6 h preservation (group 2, n = 9), and 6 h preservation followed by PGE₁ infusion (group 3, n = 9). After cold storage, the grafts were put on the recirculating IPRL system, then reperfused for 120 min at 37°C with oxygenated Krebs-Henseleit buffer containing hyaluronic acid (HA). To examine the function of the sinusoidal endothelial cells and hepatocytes, serial measurements of HA, tumor necrosis factor-α (TNFα), thromboxane B₂ (TXB₂), acid phosphatase, and conventional parameters in the perfusate were made. After perfusion, the trypan blue exclusion test was performed to assess the presence of any microscopic sinusoidal lining cell damage. In group 3, the bile output and HA clearance were significantly greater, while glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, TNFα, TXB₂, and acid phosphatase in the perfusate were significantly lower than in group 2. Histologically, less endothelial cell damage and hepatocyte damage than in group 2 was also confirmed. These results therefore suggest that the improvement of hepatic graft viability by PGE₁ administration is mainly due to sinusoidal endothelial cell protection. (Received for publication on Nov. 21, 1996; accepted on Nov. 6, 1998)     

Effect of low-dose infusion of prostaglandin E1 on vecuronium-induced neuromuscular blockade

The effect of low-dose (20 ng·kg⁻¹·min⁻¹) infusion of prostaglandin E₁ (PGE₁) on vecuronium-induced neuromuscular blockade was studied. The study population consisted of 24 elderly patients (65–75 years old) and 24 younger adult patients (25–56 years old). They were randomly assigned to the control and PGE₁ groups. The steady-state dose requirement (SSDR) of vecuronium was derived from ondemand infusion of the drug which produced a stable twitch height of 20% of its baseline reading, and recovery time after steady-state infusion was defined as the time for recovery from twitch height from 25% to 75%. The patients in the PGE₁ group received an infusion of PGE₁ 20 ng·kg⁻¹·min⁻¹, while those in the control group received an infusion of normal saline. The SSDR (23.2±9.1 and 34.2±5.9 μg·kg⁻¹. hr⁻¹, respectively;P=0.02) was significantly less and the recovery time (35.0±9.5 and 19.9±4.2 min, respectively;P=0.01) was significantly longer in the elderly than in the younger patients. However, low-dose infusion of PGE₁ significantly increased the SSDR (23.2±9.1 to 37.4±3.7 μg· kg⁻¹·hr⁻¹;P=0.01) and shortened the recovery time (35.0±9.5 to 23.5±4.0 min;P=0.02) in elderly patients. We concluded that low-dose infusion of PGE₁ is effective in preventing the prolonged action of vecuronium in elderly patients.     

The effect of Intraportal PGE1 on Warm Ischemic Liver Damage

To determine the most effective route of administering prostaglandin E₁ (PGE₁) to inhibit warm ischemic liver damage, 90-min warm ischemia was established in a canine model. The dogs were divided into three groups according to the treatment given. Thus, group A (n = 10) was the control group which received no treatment, group B (n = 7) was administered PGE₁ intravenously, and group C (n = 7) was administered PGE₁ intraportally. PGE₁ was continuously administered before and after the ischemia at a rate of 0.02⦰/min. The branched-chain amino acid to aromatic amino acid ratio in the hepatic vein, and the arterial ketone body ratio of acetoacetic acid to -hydroxybutyric acid, were examined to observe the metabolism of each amino acid and the oxidation-reduction ability of hepatocytes. Both ratios were maintained only in the group C dogs, three of which survived for over 3 days, whereas in groups A and B, all the dogs died within 24h. The results of this study imply that the intraportal administration of PGEI was more effective against warm ischemic liver damage than the intravenous administration of PGE₁.     

Reduction of dietary magnesium by only 50% in the rat disrupts bone and mineral metabolism

Introduction The objective of this study was to determine the effect of a moderate reduction of dietary magnesium [50% of nutrient requirement (50% NR)] on bone and mineral metabolism in the rat, and to explore possible mechanisms for the resultant reduced bone mass. Methods Female rats were 6 weeks of age at the start of study. Serum magnesium (Mg), calcium (Ca), parathyroid hormone (PTH), 1,25(OH)₂-vitamin D, alkaline phosphatase, osteocalcin, and pyridinoline were measured during the study at 3- and 6-month time points in control (dietary Mg of 100% NR) and Mg-deficient animals (dietary Mg at 50% NR). Femurs and tibias were also collected for mineral content analyses, micro-computerized tomography, histomorphometry, and immunohistochemical localization of substance P, TNFα, and IL-1β at 3 and 6 months. Results Although no significant change in serum Mg was observed, Mg deficiency developed, as assessed by the reduction in bone Mg content at the 3- and 6-month time points (0.69±0.05 and 0.62±0.04% ash, respectively, in the Mg depletion group compared to 0.74±0.04 and 0.67±0.04% ash, respectively, in the control group; p=0.0009). Hypercalcemia did not develop. Although serum Ca level remained in the normal range, it fell significantly with Mg depletion at 3 and 6 months (10.4±0.3 and 9.6±0.3 mg/dl, respectively, compared to 10.5±0.4 and 10.1±0.6 mg/dl, respectively, in the control group; p=0.0076). The fall in serum Ca in the Mg-depleted animals was associated with a fall in serum PTH concentration between 3 and 6 months (603±286 and 505±302 pg/ml, respectively, although it was still higher than the control). The serum 1,25(OH)₂-vitamin D level was significantly lower in the Mg depletion group at 6 months (10.6±7.1 pg/ml) than in the control (23.5± 12.7 pg/ml) (p<0.01 by the t-test). In Mg-deficient animals, no difference was noted in markers of bone turnover. Trabecular bone mineral content gain was less over time in the distal femur with Mg deficiency at 3 and 6 months (0.028±0.005 and 0.038±0.007 g, respectively, compared to 0.027±0.004 and 0.048±0.006 g, respectively, in the control group; p<0.005). Histomorphometry at these time points demonstrated decreased trabecular bone volume (15.76±1.93 and 14.19±1.85%, respectively, compared to 19.24±3.10 and 17.30±2.59%, respectively, in the control group; p=0.001). Osteoclast number was also significantly increased with Mg depletion (9.07±1.21 and 13.84±2.06, respectively, compared to 7.02±1.89 and 10.47±1.33, respectively, in the control group; p=0.0003). Relative to the control, immunohistochemical staining intensity of the neurotransmitter substance P and of the cytokines TNFα and IL-1β was increased in cells of the bone microenvironment in the Mg depletion group, suggesting that inflammatory cytokines may contribute to bone loss. Conclusion These data demonstrate that Mg intake of 50% NR in the rat causes a reduced bone mineral content and reduced volume of the distal femur. These changes may be related to altered PTH and 1,25(OH)₂-vitamin D formation or action as well as to an increase release of substance P and the inflammatory cytokines TNFα and IL-1β.     

Calcium mobilization in liver transplantation graft with warm ischemia

The influence of warm ischemia on calcium mobilization in liver transplantation was investigated. Twenty-four porcine orthotopic liver transplantations were performed by a temporary portal arterialization technique. Swine were divided into three groups according to warm ischemia time; I (0 min,n=9), II (30 min,n=8), and III (60min,n=7). Ionized calcium was measured in arterial and hepatic venous blood, in initial perfusate, and in initial perfused blood. In group I, all the pigs survived, while in group III all succumbed. In group II, four survived and four died. Ionized calcium level in influx showed no differences, but the level in the initial perfusate in group I was significantly higher than that in group III. The level in the initial perfused blood in group I was significantly higher than levels in groups II and III. Retrospective analysis in group II showed that ionized calcium value in the initial perfused blood in the survivors was significantly higher than that in the non-survivors. A substantial amount of ionized calcium accumulated after revascularization in the graft loaded with warm ischemia, and, in group II, significantly more ionized calcium accumulated in the non-survivors.     

A high level of prostaglandin E2 (PGE2) in the portal vein suppresses liver-associated immunity and promotes liver metastases

Prostaglandin E₂ (PGE₂) is generally accepted to be an immunosuppressant produced by cancer cells and their surrounding macrophages. Although several investigators have reported detecting high concentrations of PGE₂ in the portal veins of patients with colorectal cancer, the relationship between these high concentrations of PGE₂ in the portal vein and liver-associated immunity remains unclear. In this study, we attempted to determine if the portal administration of PGE₂ suppresses the immune function of the liver in a rat model. Donryu rats were administered PGE₂ via the portal vein for 7 days, following which the cytotoxic activity of hepatic sinusoidal lymphocytes (HSL) against natural killer (NK)-sensitive YAC-1 and rat syngeneic AH60C tumor cells was assessed. Purified HSL are spontaneously cytolytic; however, the continuous administration of PGE₂ dramatically suppressed the cytotoxic activity of HSLs in a dose-dependent fashion. Flow cytometric analysis showed that the large granular lymphocyte (LGL) fraction, hepatic natural killer (pit) cells, and CD4^–8⁺ killer/suppressor T cells were mainly reduced in number in the HSLs following PGE₂ infusion. In this rat AH60C metastasis model, the continuous administration of PGE₂ increased the number and size of metastatic tumor nodules in the liver, suggesting that high concentrations of PGE₂ in the portal vein suppress liver-associated immunity and promote the formation of hepatic metastasis.     

The effect of endogenous estrogen fluctuation on metabolism of 25-hydroxyvitamin D

Summary To test the hypothesis that estrogen modulates the metabolism of 25-hydroxyvitamin D (25(OH)D) to 1,25-dihydroxyvitamin D (1,25(OH)₂D) and 24, 25-dihydroxyvitamin D (24, 25(OH)₂D), we studied 20 normal premenopausal women at four consecutive weekly intervals during one menstrual cycle. Estrogen stimulation was semiquantitatively defined into baseline, lowgrade, or medium-grade categories, based on endogenous estrone and estradiol concentrations. 1,25(OH)₂D increased incrementally from baseline levels of 34±3(SE) pg/ml to 39±3 pg/ml (P=0.2) with low-grade estrogen stimulation and to 43±3 pg/ml (P<0.05) with medium-grade estrogen stimulation, while 25(OH)D, 24,25(OH)₂D, vitamin D binding protein, parathyroid hormone, calcium, and phosphate did not change. 24,25(OH)₂D was correlated to 25(OH)D at baseline (r=0.65,P<0.01) and with low-grade estrogen stimulation (r=0.062,P<0.01), but not with medium-grade stimulation (r=0.13); these relationships are consistent with the concepts that 25(OH)D is metabolized predominantly to 24,25(OH)₂D at low estrogen levels, but not at higher estrogen levels. We conclude that endogenous estrogen elevation promotes formation of 1,25(OH)₂D from 25(OH)D, and that it may reciprocally inhibit synthesis of 24,25(OH)₂D.     

Effects of prostaglandin E2 and F2α on the skeleton of osteopenic ovariectomized rats

This article contains the histomorphometric evaluation of the effects of prostaglandin F_2α (PGF_2α on cancellous bone from the lumbar vertebra and cortical bone from the tibial shaft of ovariectomized, osteopenic rats. These effects were then compared with those of prostaglandin E₂ (PGE₂). Three-month-old rats were either ovariectomized (ovx) or shamovx. Then, either PGF_2α or PGE₂ in doses of 1 and 3 mg/kg/day was given subcutaneously for 21 days at 150 days post ovx. Histomorphometric analysis was performed separately on both the primary and secondary spongiosae of the fourth lumbar vertebral bodies (LVB) and on tibial shafts. The ovx rats exhibited osteopenia in both primary (−23% to −37%) and secondary (−20%) spongiosae of the LVB, but not in the tibial shafts at 150 and 171 days post ovx. In the LVB, PGE₂ in doses of 1 or 3 mg/kg/day for 21 days restored trabecular bone volume to the levels of sham-ovx controls in the primary spongiosa. However, in the secondary spongiosa, the treatments only thickened the trabeculae. The effects of the PGF_2α treatment were similar to those of the PGE₂ in both the primary and the secondary spongiosae. While both PGF_2α and PGE₂ treatments stimulated bone formation in the LVB as indicated by the increases in labeled perimeter, tissue and bone area-based bone formation rates, PGE₂ is about 10 times more potent than PGF_2α in these effects. The PGE₂ treatment also elevated activation frequency in the LVB, while the PGF_2α treatment did not. The treatments differed in that PGE₂ at these dose levels did not alter the eroded surface in the LVB while PGF_2α decreased it significantly. Thus, the increase of the ratio of labeled to eroded perimeter in the LVB in PGF_2α treated animals was much more than that in PGE₂-treated animals. In the tibial shafts, PGE₂ in doses of I and 3 mg/kg/day produced new marrow trabeculae in 2 of 6 and 3 of 6 of the ovx rats. However, no new trabecula was found in PGF_2α treated tibial shafts. Higher doses of PGE₂ also increased periosteal labeled perimeter, MAR, and BFR/BS, while PGF_2α did not produce any significant change in these parameters. Both PGE₂ and PGF_2α in doses of 1 and 3 mg/kg/day increased the labeled perimeter, MAR and BFR/BS and decreased the eroded perimeter in the endocortical surface. We concluded that both PGF_2α and PGEE₂ in doses of 1 and 3 mg/kg/day for 21 days exhibited anabolic bone effects. The effects were mostly confined to an increase in trabecular volume in the primary spongiosa of the LVB and in the endocortical surface of tibial shafts. The tissue level mechanism behind this appears to be that PGEE₂ and PGF_2α can both stimulate osteoblast recruitment and activity. Overall, we found PGE₂ to be more potent than PGF_2α at the same dose level at the endocortical surface. Furthermore, new marrow trabecular bone formed only after PGE₂ treatment. PGF_2α differed from PGE₂ by significantly reducing the trabecular eroded surface in ovx rats.     

An in vitro evaluation of prostaglandin El and E2 on hypothermic injury to immature myocytes

The purpose of this study was to evaluate the functional and biochemical effects of Prostaglandin E₁ (PGE₁) and prostaglandin I₂ (PGI₂) on cardiac myocytes incubated under hypothermic conditions. Cardiac myocytes were isolated from neonatal rat ventricles and cultured for 4 days with MCDB 107 medium. Following this, 12.5 × 105 myocytes/ flask were incubated at 4°C for 24 h in media with PGE₁, at concentrations of 0 M (group E0), 10^–9M (group El), 10^–8M (group E2), 10^–7 M (group E3), or 10^–6 M (group E4); or with PGI₂ at concentrations of 0 M PGI (group I0), 10^–9M (group I1), 10^–8M (group I2), 10^–7 M (group I3), or 10^–6 M (group I4). After hypothermic incubation, creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were measured, and the myocytes were then cultured for 24 h at 37°C to evaluate the recovery of the myocyte beating rate. Of the PGI₂ groups, only group 12 recovered significantly more than the control group (group I0), at 47.9 ± 28.5% (mean ± SD) of the control, being the beating rate prior to hypothermic incubation, whereas it was 18.1 ± 9.7% in group I0 (P < 0.025); however, there were no significant differences among the PGE₁ groups. Moreover, the release of CPK and LDH was significantly suppressed in group_I2 compared to the control, being 57.7 ± 27.6 mIU/flask (P < 0.05) and 275.1 ±83.0mIU/flask (P < 0.025), respectively, in group 12, and 96.8 ± 38.3 mIU/flask and 439.6 ± 147.1 mIU/flask in group I0. Again, no significant differences were observed among the PGE₁ groups. In conclusion, PGI2 was found to have a direct cytoprotective effect on immature myocytes which suggests that PGI₂ may promote cardiac preservation in the neonatal period.     

Administration of MgSO4 failed to improve the neurological recovery after complete global brain ischemia in dogs

The cerebral protective effects of MgSO₄ after complete global brain ischemia were evaluated with EEG, evoked potentials (EP) and the neurological recovery score (NRS) in the dog. Complete global brain ischemia for 15 min was achieved by occluding the ascending aorta and the caval veins. The MgSO₄ group (N=7) were injected with a 10% MgSO₄ solution and the control group (N=7) were administered a normal saline intravenously from the beginning of the resuscitation to 48 h after ischemia. The EEG grades (1=normal, 5=flat) in the control group and the MgSO₄ group were 3.9±0.1 (mean ±SEM) and 3.7±0.3, and the EEG-EP scores (6=normal, 0=serious deterioration) were 2.6±0.4 and 2.7±0.4 4h after ischemia, respectively. The 7-day survival rates for ischemia were equal in both groups (5/7:71%). The NRSs (0=death, 100=normal) in the control group and the MgSO₄ group were 50±3 (n=7) and 43±9 (n=7) on the 3rd day after ischemia, and were 56±5 (n=5) and 42±12 (n=5) on the 7th day. The differences between the two groups were not significant. We conclude that MgSO₄ administered after ischemia has no beneficial effects on the recovery of EEG, EP and the NRS after 15 min of complete global brain ischemia in the dog.     

Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum is safe even for high-risk patients

Background Because of absorbed carbon dioxide (CO₂) and elevated intraabdominal pressure (IAP), CO₂ pneumoperitoneum (CO₂PP) has potentially harmful intraoperative circulatory and ventilatory effects. Although not clinically significant for healthy patients, these effects are assumed to be deleterious for patients with a high risk for anesthesia (American Society of Anesthesiology [ASA] 3 and 4) and significant cardiopulmonary, renal, or hepatic diseases. The authors assessed CO₂PP-related adverse effects by comparing ASA 3 and 4 patients who underwent laparoscopic cholecystectomy (LC) with or without CO₂PP. Methods A total of 20 successive ASA 3 and 4 patients who underwent LC were randomized into CO₂PP (n = 10) and abdominal wall elevator (Laparolift) (n = 10) groups. The parameters for perioperative hemodynamics, ventilation, perfusion of intraabdominal organs, and blood chemistry were recorded periodically from before the induction of the anesthesia until postoperative day 2 and compared between the groups. Results Mean age, height, weight, the proportional number of ASA 3 vs ASA 4 patients, the volume of perioperative fluid loading, and the dose of analgesics did not differ significantly between the groups. The length of the operation was 49.9 ± 10.6 min for the CO₂PP group and 50.6 ± 17.2 min for Laparolift group (nonsignificant difference). The mean central venous pressure (CVP) 30 min after insufflation was higher (12.3 ± 4.8 vs 7.9 ± 3.7 mmHg) and the (Gastric Mucosal pH) pHi at the end of the operation was lower (7.29 ± 0.07 vs 7.35 ± 0.04) in the CO₂PP group than in the Laparolift group (p < 0.05). Later, CVP and pHi did not differ significantly. Other parameters of hemodynamics including oxygenation, perfusion, and blood chemistry did not differ significantly. Conclusions For LC for patients with an ASA 3 and 4 risk for anesthesia, no significant adverse effects could be attributed to CO₂ pneumoperitoneum. For high-risk patients, preoperative preparation and active perioperative monitoring are essential for safe anesthesia for LC with or without CO₂PP.     

Biocompatibility of Heparin-Coated Membrane Oxygenator During Cardiopulmonary Bypass

Abstract: The biocompatibility of the cardiopulmonary bypass (CPB) circuit, in which an oxygenator is solely heparinized, was assessed by systemic inflammatory reactions as an indicator during CPB. Fourteen patients, 11 males and 3 females, underwent coronary artery bypass surgery and were randomly divided into 2 groups of 7 patients each. For the heparin–coated oxygenator group (Group H), a heparin–coated membrane oxygenator was used in the CPB circuit, and in the control (Group C) an uncoated membrane oxygenator was employed. Systemic inflammatory reactions, such as platelet activation, prostaglandin production, complement activation, and activated granulocyte released substance, were measured prior to, during, and 6 h after CPB. The number of platelets decreased after protamine administration in both groups (14. 5 ±4. 7 times 10⁴/μl in Group H and 13. 8 ± 8. 7 times 10⁴/μd in Group C) and returned to baseline levels in Group H while it remained decreased in Group C at 6 h after CPB. The platelet factor 4 level was significantly lower in Group H (181 ± 40 ng/ml) than in Group C (297 ±131 ng/ml) after protamine administration. Thromboxane–B₂ (TXB₂) rose during CPB in both groups; however, there were significantly different levels of TXB₂ between the 2 groups at 60 min after CPB (293±258 pg/ml in Group H versus 408 ± 120 pg/ml in Group C) and after protamine administration (259 ± 122 pg/ml in Group H versus 709 ± 418 pg/ml in Group C). Plasma concentrations of granulocyte elastase were significantly lower in Group H at 30, 60 and 90 min, immediately after, and post–CPB than those of Group C. Although the oxygenator was solely heparinized in the CPB circuit, it was sufficiently effective to reduce inflammatory reactions during coronary artery bypass operation, and the heparin–coated surface seems to be more endothelium–like.     

The effects of bicarbonate and acetate haemodialysis on platelet cyclic AMP concentration,thromboxane B2 release and aggregation

The effects of chronic uraemia and serial acetate (HDA) or bicarbonate (HDB) hacmodialysis on the aggregation, thromboxane B₂ (TXB₂) release and cyclic AMP (cAMP) concentration of platelets from arterial blood were studied in 14 uraemic patients (6 dialysed and 8 conservatively treated) and 10 controls. Platelets from uraemic patients, either dialysed or treated conservatively, exhibited a significantly higher cAMP level (P<0.005), a lower TXB₂ level (P<0.01), and a lower aggregability (P<0.001) than the controls. The platelet cAMP level was more markedly decreased after HDB than after HDA (P<0.05). Greater increases in platelet aggregation (P<0.05) and TXB₂ formation were observed after HDB than after HDA. The concentration of platelet cAMP and aggregability, and also the platelet cAMP and the TXB₂ level showed a significantly negative correlation (r=–0.7,P<0.05 andr=–0.60,P<0.05, respectively). There was a positive correlation between the platelet-derived TXB₂ and the aggregability (r=0.67,P<0.05). Although most patients had secondary hyperparathyroidism, the serum parathyroid hormone level did not correlate closely with the cAMP, TXB₂ or aggregation results. The dysfunction of uraemic platelets accompanied by a reduced TXB₂ release may be explained by an increased cAMP and a decreased arachidonic acid availability. HDB improves the platelet function to a greater degree than does HDA.     

The protective effect of thromboxane A2 synthetase inhibitor against ischemic liver injury

To evaluate the role of thromboxane A₂ (TXA₂) in ischemic liver injury, the serum changes in thromboxane B₂ (TXB₂) and 6-keto-prostaglandin F₁ alpha (6-K-PGF₁) following warm ischemia of the total canine liver were examined, and the protective effect of a TXA₂ synthetase inhibitor was assessed. Total liver ischemia was performed for 60 min on two groups of dogs: a control group, in which ischemia alone was performed, and an OKY-046 group, which received a TXA₂ synthetase inhibitor. A temporary active portacaval shunt was used to eliminate the effects of splanchnic venous stasis during clamping of the hepatic pedicle. Postoperative changes in liver function, assessed by the transaminase enzyme levels, and in prostaglandins were recorded and the histologic liver findings of both groups 1 week after ischemia were compared. The levels of 6-K-PGF₁ increased after reperfusion in both groups, while those of TXB₂ increased in the control group but maintained low levels in the OKY-046 group. Liver function was better and histologic changes less marked in the OKY-046 group than in the control group, suggesting the important role of TXA₂ in ischemic liver injury and the usefulness of a TXA₂ synthetase inhibitor for protecting the liver against ischemic injury.     

Early manifestations of vitamin D effects in rat osteogenic sarcoma cells

Summary We have recently demonstrated that 48 hour exposure of ROS 17/2 cells to low concentrations of 1,25-dihydroxycholecalciferol (1,25-(OH)₂D₃) (1.0 pg/ml) stimulated the cellular accumulation of⁴⁵Ca, and exposure to high concentrations (160 pg/ml) inhibited such accumulation. In the present study, short-term (15 min) effects of the sterol on⁴⁵Ca accumulation in ROS 17/2 cells were compared with the long-term (48 hours) effects in order to clarify mechanisms responsible for 1,25(OH)₂D₃ control of calcium metabolisms in ROS 17/2 cells. ROS 17/2 cells were grown for 48 hours in the presence and absence of 1,25(OH)₂D₃ and then incubated for an additional 15 min in the presence and absence of 1,25(OH)₂D₃ immediately before measuring⁴⁵Ca accumulation. Cellular⁴⁵Ca was measured after incubating the cells in the medium containing 0.5 μCi/ml of⁴⁵CaCl₂ for 4 min at 25°C. The effect of actinomycin D was determined by preincubating the cells in 0.1 μg/ml of actinomycin D for 45 min at 25°C. Exposure to low concentrations (1.0 pg/ml) of 1,25(OH)₂D₃ for either 48 hours or 15 min increased⁴⁵Ca in the cells by 10–20%. An additional 15 min exposure following 48 hour exposure yielded an increase in the cellular⁴⁵Ca similar to that after 48 hours or 15 min exposure. Exposure to high concentrations (160 pg/ml) for either 48 hour or 15 min decreased cell⁴⁵Ca by approximately 20%.An additional 15 min exposure to the high concentrations did not change the 48 hour effect. Actinomycin D reversed early inhibitory effects of high concentrations, but had no effect on the early stimulatory effects of low concentrations. These results suggest that the mechanisms underlying the 15 min and 48 hour effects of 1,25(OH)₂D₃ are the same. Moreover, the mechanism responsible for the inhibitory effect of high concentrations is dependent onde novo protein synthesis whereas that for the stimulatory effects of low concentrations is not.     

Prostaglandin E2 binding and cyclic AMP production in isolated bone cells

Summary The binding of prostaglandin E₂ (PGE₂) to bone cells was studied to provide direct evidence for the existence of specific receptors in bone. Bone cells were isolated by collagenase digestion of fetal and newborn rat calvaria. Isolated cells were incubated with³H-PGE₂ and collected on Millipore filters. Specific binding was determined by subtracting the binding that occurred with 10⁻⁶ M non-radioactive PGE₂ and³H-PGE₂ from that with³H-PGE₂ alone. With heterogeneous cell preparations and at PGE₂ concentrations from 10⁻⁹ − 1.7 × 10⁻⁸ M at 37°C, specific binding reached steady state within 10 min. Bound³H-PGE₂ was displaced by the addition of increasing amounts of unlabeled PGE₂. Inhibition of PGE₂ binding was observed with PGE₁ and the endoperoxide analog, U44069, but not with PGE_2α, a lipopolysaccharide, or 13,14-dihydro 15-keto PGE₂. Studies with bone cell populations, obtained by sequential digestions, indicated that an osteoclastic population binds 30-fold more PGE₂ than osteoblastic cells. Scatchard analyses revealed that the osteoclastic cells have an affinity constant for PGE₂ binding similar to that obtained with heterogeneous populations. However, the PGE₂ binding capacity in this osteoclastic population was fivefold greater than in the heterogeneous population. The osteoclastic population responded with an increase in cyclic AMP to lower concentrations of PGE₂ than the osteoblastic populations. These studies suggest that differences in the binding capacity of PGE₂ receptors exist among bone celltypes and that these differences are reflected in the cellular cyclic AMP response.     

Evidence for abnormal regulation of circulating 1α,25-dihydroxyvitamin D in patients with pulmonary tuberculosis and normal calcium metabolism

Summary Available evidence indicates that hypercalcemia in pulmonary tuberculosis results from increases in circulating 1α,25-dihydroxyvitamin D [1α,25(OH)₂D]. To further characterize vitamin D metabolism in this disorder, the effects of vitamin D, 100,000 units a day for 4 days, were compared in 25 normal subjects and 11 patients with active pulmonary tuberculosis who were normocalcemic and had not had hypercalcemia. Serum calcium, phosphorus, 25-hydroxyvitamin D (25-OHD) and 1α,25(OH)₂D were measured. Whereas vitamin D increased mean serum 25-OHD from 20±2 (±SE) to 40±5 ng/ml (P<0.001) and did not change mean serum 1α,25(OH)₂D in the normals (33±2 vs. 31±2 pg/ml), it increased mean serum 25-OHD from 21±4 to 55±13 ng/ml (P<0.05) and mean serum 1α,25(OH)₂D from 28±2 to 35±3 pg/ml (P<0.05) in the patients. Serum calcium was normal and remained within the normal range in all subjects and patients. The findings indicate that there is a modest but significant abnormality in the regulation of circulating 1α,25(OH)₂D in normocalcemic patients with pulmonary tuberculosis. The results are similar to those previously reported by us in normocalcemic patients with sarcoidosis.     

Comparative hemodynamic effects of hypotension induced by CGRP and PGE1 in dogs

Calcitonin gene-related peptide (CGRP) produces vasodilation, hypotension, and tachycardia. We compared the hemodynamic effects of CGRP-induced hypotension with the effects of prostaglandin E₁ (PGE₁), which is currently used as a hypotensive agent during anesthesia. Eighteen mongrel dogs were anesthetized with pentobarbital (25 mg·kg⁻¹), and 0.87% halothane in oxygen (1MAC). Measurements of hemodynamic variables were made before, during, and after induced hypotension. The mean arterial pressure (MAP) was lowered to 60 mmHg by the infusion of either CGRP (n=10) or PGE₁ (n=8). This decrease in MAP was appoximately 50% of the baseline value. The CGRP- and PGE₁-induced hypotension resulted in 61% and 51% maximum reductions (P<0.01, respectively) in systemic vascular resistance associated with a significant increase in stroke volume index; the two treatments, however produced inconsistent changes in cardiac index (CI). With CGRP, a maximum increase of 144% (P< 0.01) in CI was observed during induced hypotension. In contrast, PGE₁-induced hypotension caused no significant changes in CI throughout the observation period. Left ventricular maximum dP/dt decreased (P<0.01) during the hypotensive period with PGE₁, whereas it remained un-changes during CGRP-induced hypotension. The different results for changes in CI and cardiac contractility during the CGRP- and PGE₁-induced hypotension were probably due to differences in ventricular filling pressure. Hypotension induced by PGE₁ was associated with a significant decrease in heart rate (HR), whereas CGRP did not affect HR. This study shows that both CGRP and PGE₁ are effective in decreasing afterload and in inducing hypotension; the results suggest that CGRP is a useful vasodilator for inducing hypotension during halothane anesthesia. This study was presented, in part, at the Annual Meeting of the American Society of Anesthesiologists, October, 1993, Washington DC, and at the 41st Annual Meeting of the Japan Society of Anesthesiology, April, 1994, Tokyo This study was supported by a Grant-in-Aid (No 04807115) for Scientific Research (C) from the Ministry of Education, Science, Sports, and Culture, Japan