The effect of glucocorticoid administration on bacterial translocation. Evidence for an acquired mucosal immunodeficient state.

Adherence of bacteria to intestinal epithelial cells may be the crucial initiating event for translocation and is normally prevented by both specific (secretory IgA) and nonspecific (mucus, bacterial antagonism, desquamation) mucosal defense mechanisms. The purpose of this study was to examine the effect of dexamethasone administration on mucosal immunity; specifically bacterial adherence and IgA. Twenty Fischer rats were randomly assigned to two groups of 10 animals each. Group I received 0.5 mL saline injection intraperitoneally (IP); and group II, 0.8 mg/150 g body weight dexamethasone IP per day for 2 consecutive days. The cecum mesenteric lymph nodes, and bile were aseptically collected, and bacterial adherence, bacterial translocation, and IgA concentration were determined. Results indicate that, compared with saline-treated animals, dexamethasone-treated animals had a fall in IgA (54 +/- 24 versus 232 +/- 41 micrograms/mg protein), an increase in bacterial adherence (8.2 +/- 0.5 versus 3.4 +/- 0.6 cfu (log10)/g cecum), and an increased incidence of bacterial translocation to the mesenteric lymph nodes (60% versus 0%). These data suggest that glucocorticoids may promote bacterial translocation by impairment of mucosal IgA synthesis.     

Endotoxin and renal glutamine metabolism.

The effect of endotoxin on renal glutamine metabolism and ammoniagenesis was investigated in vivo in the rat to gain further insight into the altered glutamine flow that characterizes critical illness. Studies were done 15 hours following a single dose of Escherichia coli lipopolysaccharide (10 mg/kg). Renal blood flow and arterial glutamine concentration were similar in control and study rats, but the kidney switched from an organ of slight glutamine uptake in controls (129 +/- 52 nmol/100 g of body weight per minute) to net release in the endotoxin-treated animals (-273 +/- 170 nmol/100 g of body weight per minute). Simultaneously, the specific activity of renal glutamine synthetase increased by almost 50% (374 +/- 40 nmol/mg of protein per hour in rats given endotoxin vs 253 +/- 12 nmol/mg of protein per hour in controls), while glutaminase was unchanged. Urinary ammonia excretion was reduced by 35% in the endotoxin-treated animals (47 +/- 6 mumol/12 h in endotoxin-treated animals vs 70 +/- 8 mumol/12 h in controls) despite a 10% fall in the arterial bicarbonate value. Endotoxin alters the net flux of glutamine across the kidney which appears to be partially regulated enzymatically. This may impair the kidneys' ability to maintain acid/base homeostasis.     

Effects of glucocorticoids on lung glutamine and alanine metabolism

The role of the glucocorticoid hormones as possible mediators of the accelerated lung glutamine and alanine release that occurs during critical illness was investigated. Studies were done in adult rats receiving dexamethasone (0.6 mg intramuscularly/100 gm body weight/day for 2 consecutive days; n = 24) or saline solution (controls; n = 20). Measurements were made in the postabsorptive state and amino acid flux was calculated by multiplying pulmonary blood flow by the right ventricular-arterial concentration difference for glutamine and alanine. Lung glutamine release was 703 +/- 184 nmol/100 gm body weight/min in control rats. This release rate doubled in the dexamethasone-treated rats (1476 +/- 256; p less than 0.05). The activity of the glutamine synthetase enzyme increased by 33% in the dexamethasone-treated animals and there was a 50% decrease in lung glutamine content (p less than 0.01). Likewise, dexamethasone accelerated the release of alanine by the lungs twofold (559 +/- 173 nmol/100 gm body weight/min in controls vs 1113 +/- 184 nmol/100 gm body weight/min in dexamethasone-treated rats; p less than 0.05). The increased release of both amino acids was caused by a significant increase in the concentration difference across the lungs and not a change in pulmonary blood flow. Glucocorticoids appear to be key mediators of the accelerated lung amino acid release that characterizes catabolic diseases.     

Modification of catecholamine and prostaglandin tissue levels in E. coli endotoxin-treated rats

Epinephrine and norepinephrine adrenal levels were depleted in Escherichia coli endotoxin-treated (10 mg/kg) male Wistar rats from 504 +/- 203 to 119 +/- 77 ng/mg in control and from 200 +/- 97 to 123 +/- 66 ng/mg wet wt, respectively. However dopamine increased from 4.2 +/- 1.9 to 14.9 +/- 3.4 ng/mg. After endotoxin administration, norepinephrine content in peripheral organs, heart 1.27 +/- 0.19 ng/mg, spleen 1.52 +/- 0.59 ng/mg, liver 0.15 +/- 0.05 ng/mg, and kidney 0.24 +/- 0.09 ng/mg wet wt. decreased by 34, 36, 47, and 18%, respectively. Indomethacin treatment kept the catecholamine levels constant in endotoxic rats, but naloxone had no effect. PGF2 alpha tissue levels (12.0 +/- 10.1 pg/mg protein in spleen and 1.85 +/- 0.6 pg/mg protein in liver) were increased twofold by endotoxin treatment: PGE2 content in spleen and liver 0.5 +/- 0.2 pg/mg protein and 2.3 +/- 1.9 pg/mg protein, respectively, increased by only 27 and 26%. In the kidneys of endotoxin-treated animals, PGF2 alpha and PGE2 levels were lower than in control. Indomethacin treatment decreased PGF2 alpha and PGE2 and increased the norepinephrine content in the same organs. It is suggested that prostaglandins play a participative role in the control of norepinephrine tissue levels in endotoxemia.     

The effects of sepsis and endotoxemia on gut glutamine metabolism.

The effects of sepsis on gut glutamine (GLN) metabolism were studied to gain further insight into the regulation of the altered glutamine metabolism that characterizes critical illnesses. Studies were done in laboratory rats and in hospitalized patients. The human studies were done in seven healthy surgical patients (controls) and six septic patients who underwent laparotomy. Radial artery and portal vein samples were obtained during operation and were analyzed for GLN and oxygen content. Despite no reduction in arterial glutamine concentration in the septic patients, gut glutamine extraction was diminished by 75% (12.0% +/- 1.6% in controls vs. 2.8% +/- 0.8% in septic patients, p less than 0.01). Similarly gut oxygen extraction was diminished by nearly 50% in the septic patients (p less than 0.05). To further investigate these abnormalities, endotoxin (10 mg/kg intraperitoneally) or saline (controls) was administered to adult rats 12 hours before cannulation of the carotid artery and portal vein. The arterial GLN concentration was increased by 13% in the endotoxin-treated animals (p less than 0.05) but gut glutamine uptake was diminished by 46% (526 +/- 82 nmol/100 g BW/minute in controls vs. 282 +/- 45 in endotoxin, p less than 0.01). Simultaneously gut glutaminase activity was diminished by 30% (p less than 0.01) and intestinal glutamate release fell by two thirds. Blood cultures were negative in control animals (0 of 20), but were positive in 25% of endotoxemic animals (6 of 24) for gram-negative rods (p = 0.019). Sepsis and endotoxemia impair gut glutamine metabolism. This impairment may be etiologic in the breakdown of the gut mucosal barrier and in the development of bacterial translocation.     

Dexmedetomidine in combination with morphine PCA provides superior analgesia for shockwave lithotripsy

PURPOSE: To compare the analgesic effects of dexmedetomidine/morphine with those of tramadol/midazolam in patients undergoing extracorporeal shockwave lithotripsy (ESWL) for urinary calculi. METHODS: Sixty patients were randomized to receive either dexmedetomidine 1 micro g*kg(-1) iv followed by 0.5 micro g*kg(-1)*hr(-1) infusion together with morphine patient-controlled analgesia [(PCA); 2 mg bolus, five minutes lockout, 2 mg*hr(-1) infusion; (Group DEX)], or tramadol 1.5 mg*kg(-1) pre-mixed with midazolam 30 micro g*kg(-1) iv followed by tramadol PCA [20 mg bolus, five minute lockout, 20 mg*hr(-1) infusion; (Group TRA)]. Pain was assessed at baseline and every 15 min thereafter. Patients' and urologist's satisfaction with analgesia and sedation were determined on a seven-point scale ranging from 1 (extremely dissatisfied) to 7 (extremely satisfied). Patient's discharge time was also documented. RESULTS: Visual analogue scale scores over time were consistently lower in Group DEX compared with Group TRA (P = 0.001). Patients' satisfaction with analgesia (5 +/- 1 vs 4 +/- 2, P = 0.012) and with sedation (6 +/- 1 vs 5 +/- 1, P = 0.020), and urologist's satisfaction (6 +/- 1 vs 4 +/- 2, P = 0.001) were all higher amongst Group DEX patients compared with Group TRA. There was no difference between discharge times of patients in Group DEX compared with those in Group TRA [85 (60,115) min vs 65 (40,95) min, P = 0.069]. CONCLUSION: Dexmedetomidine in combination with morphine PCA provided better analgesia for ESWL and was associated with higher patients' and urologist's satisfaction when compared with a tramadol/midazolam PCA combination.     

Time-course of cardiopulmonary effects tumor necrosis factor and endotoxin are similar.

Tumor necrosis factor (TNF) is a postulated proximal septic mediator. The authors compared the time course and extent of the cardiopulmonary effects of recombinant human TNF (rTNF) in swine vs those of Escherichia coli endotoxin (ETX). Intravenous boluses of either rTNF (n = 4), ETX (n = 2), or saline (n = 4) were given to swine. Mean pulmonary artery pressure and extravascular lung water (EVLW) were increased at 60 minutes for rTNF and ETX to 31 +/- 2 mmHg and 33 +/- 3 mmHg and 6.3 +/- 0.9 ml/kg and 7.1 +/- 1.6 ml/kg, while saline animals were unchanged. The authors conclude that rTNF mimics ETX both in time course and magnitude of effects. Right-sided cardiopulmonary effects predominate in both with minimal left-sided effects at these dosages. The time course of early increased EVLW suggests an initial hydrostatic influence on pulmonary edema formation in this septic model.     

Improvement of rejection-induced diastolic abnormalities in rat cardiac allografts with inducible nitric oxide synthase inhibition

OBJECTIVE: Inhibition of inducible nitric oxide synthase (nitric oxide II) activity has been proposed as a method to attenuate capillary leak and edema during rejection of heterotopically transplanted rat hearts. Myocardial edema has previously been implicated in diastolic dysfunction during allograft rejection. Accordingly, we tested the hypothesis that inducible nitric oxide synthase inhibition with aminoguanidine would alleviate left ventricular stiffening and myocardial edema formation in 4-day heterotopic rat heart allografts. METHODS: Passive left ventricular filling was studied in American Cancer Institute Lewis rats receiving heterotopic heart transplants receiving either aminoguanidine, a selective nitric oxide synthase inhibitor (n = 6); dexamethasone (1 mg. kg(-1). d(-1) administered subcutaneously) for 4 days after transplantation (n = 6); or intravenous saline solution (n = 6). American Cancer Institute-to-American Cancer Institute isografts (n = 6) were used as controls. RESULTS: Serum nitrite/nitrate levels in the aminoguanidine group (18 +/- 3 mmol/L) and dexamethasone group (22 +/- 4 mmol/L) were reduced versus the intravenous saline group (144 +/- 36 mmol/L [SEM]) to levels seen in controls (25 +/- 9 mmol/L). Left ventricular volume at 15 mm Hg for the aminoguanidine group was increased versus that for the intravenous saline solution group, similar to that for controls, and reduced versus dexamethasone-treated animals. Myocardial water content for the aminoguanidine-treated animals (78.3% +/- 0.4%) was similar to those of intravenous saline-treated animals (78.0% +/- 0. 3%) but greater than those of controls (77.1% +/- 0.2%) and dexamethasone-treated animals (76.7% +/- 0.3%). CONCLUSIONS: Nitric oxide II inhibition with aminoguanidine minimizes the reduction in left ventricular filling that is seen with allograft rejection through a mechanism that is not associated with attenuation of myocardial edema.     

雄激素对糖皮质激素致大鼠不同类型骨骼肌萎缩的拮抗作用研究

目的:探讨地塞米松对不同类型骨骼肌的致萎缩作用以及睾酮的拮抗效果.方法:雌性SD大鼠160只,随机分为4组(n=40):①对照组:前肢皮下注射芝麻油1 ml·kg-1·d-1,连续3 d后同时腹腔注射生理盐水1 ml·kg-1·d-1,每日1次;②地塞米松组:注射地塞米松1 mg·kg-1·d-1(代替生理盐水)和芝麻...     

Insulin Treatment of Corticosteroid-associated Hyperglycemia and Its Effect on Outcome after Forebrain Ischemia in Rats

Background: Recent studies have reported that dexamethasone worsens neuronal injury after brain ischemia. This effect is assumed to be secondary to drug-induced hyperglycemia. The current study used a rat model to test the hypotheses that insulin treatment of dexamethasone-induced hyperglycemia would result in a postischemic neurologic outcome that is: (1) better than that of hyperglycemic, dexamethasone-treated subjects; and (2) better than, or equal to, that of saline-treated control subjects.

Methods: Twenty-four halothane-anesthetized (1.0% inspired) rats were randomly assigned to one of three treatment groups (N = 8 in each group): (1) normoglycemic, placebo-treated rats (group P) received an intravenous saline infusion; (2) hyperglycemic, dexamethasone-treated rats (group D) received 2 mg/kg intraperitoneal dexamethasone at 2 days, 1 day, and 3 h before ischemia plus an intravenous saline infusion; and (3) normoglycemic, dexamethasone- and insulin-treated rats (group DI) received the same treatment as group D, plus an intravenous insulin infusion shortly before ischemia. Blood gases and acid-base status were maintained within normal physiologic ranges. Pericranial and rectal temperatures were maintained at normothermia. Forebrain ischemia of 10 min duration was produced using an established model. Neurologic function was assessed by a blinded observer at 24 and 48 h postischemia. Brain histopathology was assessed at the time of ischemia-related death or after the examination at 48 h. All 24 rats were included in the analysis of neurologic function; however, only 21 rats that survived for greater or equal to 24 h postischemia were included in the histologic analysis.

Results: Rats were well matched for systemic physiologic variables, with the exception of glucose concentrations. Plasma glucose concentration immediately before ischemia was as follows: group P = 129+/-8 mg/dl (mean+/-SD), group D = 344+/-29 mg/dl, and group DI = 123+/-17 mg/dl. At 48 h postischemia, groups P and DI were minimally injured and had similar functional scores. In contrast, all group D rats died of cerebral ischemia. Histologic injury was significantly worse in group D than in either group P or DI, but did not differ significantly between groups P and DI. When all groups were combined, there was a significant correlation between neurologic function and total histopathology score ranks.     

The effects of endotoxin on glutamine transport by pulmonary artery endothelial cells

The effects of endotoxin on glutamine transport by cultured pulmonary artery endothelial cells (PAECs) were studied in order to gain further insight into the regulation of the altered lung glutamine metabolism that characterizes severe infection. Incubation of PAECs with endotoxin (1 micrograms/ml) resulted in a significant increase in System ASC-mediated glutamine transport which did not occur for 8 hr and was maximal after 12 hr of exposure. Kinetic studies indicated that the increase in carrier-mediated activity was not due to a change in Km (101 +/- 6 microM in controls vs 97 +/- 4 microM in endotoxin-treated cells, P = NS), but rather to a 73% increase in Vmax (840 +/- 60 pmole/mg protein/30 sec in controls vs 1450 +/- 80 in endotoxin-treated cells, P less than 0.001). The increase in glutamine uptake by PAECs was completely blocked by actinomycin D and cycloheximide, indicating that the accelerated glutamine transport was most probably due to an increase in transporter synthesis. Endotoxin stimulates glutamine uptake by PAECs, either directly or indirectly, an adaptive response which may be necessary to support cellular metabolism, structure, and function.     

The effect of parenteral nutrition on gastrointestinal immunity. The importance of enteral stimulation.

Secretory IgA (S-IgA), an immunoglobulin present in secretions, prevents the adherence of bacteria to mucosal cells and is the principle component of the gut mucosal defense system. The purpose of this study was to determine whether the route of nutrient administration affects S-IgA. Twenty-five female Fisher rats were randomized into three groups. Groups I and II were fed an isonitrogenous, isocaloric standard hyperalimentation solution, Group I intravenously and Group II via a gastrostomy. Group III (control) was fed rat chow and water ad lib. Since bile is one of the principle sources of S-IgA, animals had biliary T-tubes placed for sampling of bile every 4 days. At day 16, Group I animals were fed rat chow and water for an additional 8 days. S-IgA was measured by the ELISA immunoassay. Results indicated at day 16 that the S-IgA level in mg/ml of Group I was 1.1 +/- 0.2, while the S-IgA in Groups II and III was 2.2 +/- 0.6 and 2.2 +/- 0.26, respectively. Furthermore, the S-IgA level in Group I after 8 days of enteral feeding rose to 1.8 +/- 0.4. The difference in S-IgA levels between enterally and parenterally fed rats suggests that an important defense barrier is compromised during parenteral hyperalimentation. Rats fed the same nutrients by gastrostomy maintained S-IgA levels better than rats fed the same nutrients intravenously. The rapid return to normal levels after resumption of enteral feeding suggests that the intraluminal presence of foodstuffs is essential for maintenance of S-IgA.     

Comparison of ketamine and pentobarbital anesthesia with the conscious state in a porcine model of Pseudomonas aeruginosa septicemia

Live Pseudomonas aeruginosa (2.5.10(9).kg-1.h-1) were administered to awake (Group A, n = 10) and anesthetized piglets, which were given intravenous ketamine (Group K, 10 mg.kg-1.h-1, n = 8) or pentobarbital (Group P, 15 mg.kg-1.h-1, n = 8). The anesthetized animals were mechanically ventilated. In addition, a pentobarbital group (Group CP, n = 6) and a ketamine control group (Group CK, n = 6) were studied. The mean survival time was 10.5 +/- 3.0 h in Group A, 10.6 +/- 2.8 h in Group K, and 1.8 +/- 1.3 h in Group P. In Group P the arterial pressure, the cardiac output and the systemic vascular resistance declined soon after start of the bacterial infusion, whereas the pulmonary artery pressure increased. The animals died of irreversible circulatory failure. In Group K pronounced pulmonary hypertension and lethal pulmonary edema developed. There was no circulatory failure in Group A, but the animals also died of marked pulmonary edema. Groups CP and CK exhibited stable hemodynamics for a period of 8 h. The results of this study suggest a deleterious effect of pentobarbital on hemodynamics and survival time, and a minor suppressive action of ketamine on the circulation in septicemia. Therefore, data obtained from septic shock studies applying pentobarbital have to be evaluated carefully. Investigation of the effects of gram-negative bacteria or endotoxin should be performed in unanesthetized or, if anesthesia is necessary, in ketamine-anesthetized animals.     

Prolonged elevation of plasma free fatty acids desensitizes the insulin secretory response to glucose in vivo in rats

Prolonged exposure of pancreatic islets to free fatty acids (FFAs) inhibits glucose-stimulated insulin secretion (GSIS) in vitro. However, FFA inhibition of GSIS has not been clearly demonstrated in vivo. We examined the in vivo effect of prolonged elevation of plasma FFAs on GSIS using a two-step hyperglycemic clamp in rats treated with a 48-h intravenous infusion of either 20% Intralipid plus heparin (INT) (5 microl/min plus heparin, 0.1 U/min; n = 8), oleate (OLE) (1.3 microEq/min; n = 6), saline (SAL) (n = 6), or bovine serum albumin (BSA) (vehicle for OLE; n = 5). Because there was no difference in any of the parameters between BSA and SAL rats, these groups were combined as control rats (CONT) (n = 11). At the end of the 48-h OLE/INT/CONT infusions, after an overnight fast, plasma glucose was clamped for 2 h at 13 mmol/l and for another 2 h at 22 mmol/l. Preclamp plasma FFAs were elevated twofold (P < 0.01) versus CONT with both INT and OLE (NS, INT vs. OLE). Preclamp glucose, insulin, and C-peptide levels were higher in INT than in CONT rats (P < 0.05), suggesting insulin resistance, but they were not different in OLE and CONT rats. The insulin and C-peptide responses to the rise in plasma glucose from basal to 13 mmol/l were lower in OLE (336 +/- 72 pmol/l and 1.2 +/- 0.1 nmol/l, P < 0.01 and P < 0.05, respectively) than in CONT (552 +/- 54 and 1.9 +/- 0.1) rats, but they were not different between CONT and INT rats (648 +/- 150 and 2.0 +/- 0.4). The insulin and C-peptide responses to the rise in plasma glucose from 13 to 22 mmol/l were lower in both INT (1,188 +/- 204 pmol/l and 3.0 +/- 0.3 nmol/l, P < 0.01 and P < 0.001) and OLE (432 +/- 60 and 1.7 +/- 0.2, P < 0.001 vs. CONT or INT) rats than in CONT rats (1,662 +/- 174 and 5.0 +/- 0.6). In summary, 1) both INT and OLE decreased GSIS in vivo in rats, and 2) the impairing effect of INT on GSIS was less than that of OLE, which might be due to the different type of fatty acid (mostly polyunsaturated in INT versus monounsaturated as OLE) and/or to differential effects of INT and OLE on insulin sensitivity. In conclusion, prolonged elevation of plasma FFAs can desensitize the insulin secretory response to glucose in vivo, thus inducing a beta-cell defect that is similar to that found in type 2 diabetes.     

Effect of prenatal dexamethasone on rat renal development

BACKGROUND: Prenatal insults can program the developing fetus to develop diseases that manifest in later life. Dexamethasone is often administered to the developing fetus to accelerate pulmonary development. The purpose of the present study was to determine whether prenatal dexamethasone adversely affects renal development and predisposes rats to develop renal disease and hypertension in later life. METHODS: Pregnant rats were given either vehicle or two daily intraperitoneal injections of dexamethasone (0.2 mg/kg body weight) on gestational days: 11 and 12, 13 and 14, 15 and 16, 17 and 18, 19 and 20, or 20 and 21. Tail cuff blood pressure, glomerular number, and inulin clearance were measured in control and prenatal dexamethasone-treated rats when the rats were 60 to 90 days of age. RESULTS: Prenatal dexamethasone did not affect the length of gestation, the number of animals per litter, or the total body weight or kidney weight measured at one day of age. Offspring of rats administered dexamethasone on days 15 and 16 gestation had a 30% reduction in glomerular number compared with control at 60 to 70 days of age (24,236 +/- 441 vs. 30,453 +/- 579, P < 0.01). Rats receiving prenatal dexamethasone on days 17 and 18 had an approximate 20% reduction in glomeruli compared with control (P < 0.01). Offspring of rats receiving dexamethasone on days 15 and 16 gestation had systolic blood pressures at 60 to 90 days of age that were higher than any other group (P < 0.05). The glomerular filtration rate was comparable in all of the groups. CONCLUSIONS: This study shows that two daily doses of prenatal dexamethasone (0.2 mg/kg body weight) in rats do not produce intrauterine growth retardation. Adult offspring of rats that received prenatal dexamethasone during specific times of gestation have a reduced number of nephrons and hypertension.     

Effect of bacterial sepsis on gluconeogenic capacity in the rat

Since sepsis places increased demands on the host for energy and on other substrates for tissue repair and host defense, hepatic gluconeogenesis is critical for the host's adaptation to sepsis. Substrate-stimulated gluconeogenesis (i.e., gluconeogenic capacity) was assessed by the alanine load method in mannoheptulose-pretreated rats made septic by cecal ligation after laparotomy, as well as by cecal ligation and puncture after laparotomy. Fasted rats subjected to laparotomy only (sham-ligated) and fasted, nonoperated rats (controls) were investigated simultaneously. Following an overnight (-18 to 0 hr) fast, nonoperated animals converted 17.9 +/- 1.5% of [14C]alanine to [14C]glucose. Continued fasting in nonoperated animals resulted in enhanced (P less than 0.05) gluconeogenic capacity (6 hr = 27.2 +/- 3.0%; 24 hr = 26.2 +/- 1.9%; and 48 hr = 28.5 +/- 2.6%) relative to Time 0. Laparotomy alone (sham ligation) delayed the fasting-induced increase (P less than 0.05) in gluconeogenesis capacity (6 hr = 21.1 +/- 1.2%; 24 hr = 18.5 +/- 1.3%; 48 hr = 27.8 +/- 1.0%) relative to Time 0. In contrast, postoperative sepsis produced a sustained depression (P less than 0.05) of gluconeogenic capacity relative to nonoperated sham-ligated controls at 48 hr (cecal ligation, 18.4 +/- 1.4%; and cecal ligation and puncture, 18.8 +/- 1.2%). Thus, (1) fasting enhances hepatic gluconeogenic capacity; (2) surgical trauma transiently blunts the gluconeogenic response to fasting; and (3) sepsis undermines the gluconeogenic response to fasting.     

The early response of the jejunal brush border glutamine transporter to endotoxemia.

The early effects of endotoxin (4 hr after a single dose of Escherichia coli LPS, 7.5 mg/kg) on L-glutamine (GLN) transport across the jejunal brush border of rats were studied. Jejunal brush border membrane vesicles (BBMVs) were prepared by a Mg2+ aggregation/differential centrifugation technique. Vesicle purity and integrity were confirmed by a 15-fold enrichment of brush border marker enzymes, osmotic activity, transport overshoots in the presence of sodium, and similar 1- and 2-hr equilibrium values. L-[3H]GLN transport in jejunal BBMVs was measured by a millipore filtration technique. Na(+)-dependent glutamine transport, which accounted for greater than 80% of total transport, was increased twofold in BBMVs from endotoxin-treated rats (67 +/- 5 pmole/mg protein/15 sec vs 38 +/- 3, P less than 0.01). Endotoxin treatment did not alter the activity of the Na(+)-independent carrier. Simultaneously, intestinal extraction of glutamine from the bloodstream fell by 56% (15.1 +/- 2.3% in controls vs 6.6 +/- 1.3% in endotoxin-treated rats, P less than 0.01). This reduction in the uptake of circulating glutamine could not be accounted for by a fall in the arterial concentration. Thus, soon after endotoxemia brush border glutamine uptake is increased while consumption of glutamine across the basolateral membrane is decreased. This increased uptake may support protein synthesis and may provide a biochemical rationale for the use of early enteral nutrition after the onset of critical illness.     

Cardiotrophin-1 attenuates endotoxin-induced acute lung injury.

Cardiotrophin-1 (CT-1) is a recently discovered member of the gp130 cytokine family, which includes IL-6, IL-11, leukemia inhibitory factor, ciliary neurotrophic factor, and oncostatin M. Recent evidence suggests that, like other members of this family, CT-1 may possess anti-inflammatory properties. We hypothesized that in vivo CT-1 administration would attenuate endotoxin (ETX)-induced acute lung injury. We studied the effects of CT-1 (100 microgram/kg ip, 10 min prior to ETX) in a rat model of ETX-induced acute lung injury (Salmonella typhimurium lipopolysaccharide, 20 mg/kg ip). Six hours after ETX, lungs were harvested for determination of neutrophil accumulation (myeloperoxidase, MPO, assay) and lung edema (wet-to-dry weight ratio). Mechanisms of pulmonary vasorelaxation were examined in isolated pulmonary artery rings at 6 h by interrogating endothelium-dependent (response to acetylcholine) and endothelium-independent (response to sodium nitroprusside) relaxation following alpha-adrenergic (phenylephrine)-stimulated preconstriction. CT-1 abrogated the endotoxin-induced lung neutrophil accumulation: 2.3 +/- 0.2 units MPO/g wet lung (gwl) vs 6. 3 +/- 0.3 units MPO/gwl in the ETX group (P < 0.05 vs ETX, P > 0.05 vs control). Similarly, CT-1 prevented ETX-induced lung edema: wet-to-dry-weight ratio, 4.473 +/- 0.039 vs 4.747 +/- 0.039 in the ETX group (P < 0.05 vs ETX, P > 0.05 vs control). Endotoxin caused significant impairment of both endothelium-dependent and -independent pulmonary vasorelaxation, and CT-1 attenuated this injury. Thus, cardiotrophin-1 possesses significant anti-inflammatory properties in a model of endotoxin-induced acute lung injury.     

Amylin and bone metabolism in streptozotocin-induced diabetic rats.

Amylin (AMY) is a 37 amino acid peptide cosecreted with insulin (INS) by pancreatic beta-cells and absent in type 1 diabetes, a condition frequently associated with osteopenia. AMY binds to calcitonin receptors, lowers plasma calcium concentration, inhibits osteoclast activity, and stimulates osteoblasts. In the present study, we examined the effects of AMY replacement on bone loss in a streptozotocin (STZ)-induced rodent model type 1 diabetes. Of 50 male Wistar rats studied, 40 were made diabetic with intraperitoneal STZ (50 mg/kg; plasma glucose concentrations > 11 mM within 5 days). Ten nondiabetic control (CONT) rats received citrate buffer without STZ. Diabetic rats were divided into four groups (n = 10/group) and injected subcutaneously with rat AMY (45 mg/kg), INS (12 U/kg), both (same doses), or saline (STZ; diabetic controls) once per day. After 40 days of treatment and five 24-h periods of urine collection for deoxypyridinoline (DPD), the animals were killed, blood was sampled, and femurs were removed. The left femur was tested for mechanical resistance (three-point bending). The right femur was tested for total, diaphyseal (cortical bone), and metaphyseal (trabecular bone) bone densities using dual-energy X-ray absorptiometry (DXA). Bone was ashed to determine total bone mineral (calcium) content. None of the treatments had any significant effect on femoral length and diameter. Untreated diabetic rats (STZ; 145+/-7N) had lower bone strength than did nondiabetic CONT (164+/-38; p < 0.05). Total bone mineral density (BMD; g/cm2) was significantly lower in STZ (0. 2523+/-0.0076) than in CONT (0.2826+/-0.0055), as were metaphyseal and diaphyseal densities. Diabetic rats treated with AMY, INS, or both had bone strengths and bone densities that were indistinguishable from those in nondiabetic CONT. Changes in bone mineral content paralleled those for total BMD (T-BMD). Plasma osteocalcin (OC) concentration, a marker for osteoblastic activity, was markedly lower in untreated diabetic rats (7. 6+/-0.9 ng/ml); p < 0.05) than in nondiabetic CONT (29.8+/-1.7; p < 0.05) or than in AMY (20.1+/-0.7; p < 0.05). Urinary DPD excretion, a marker for bone resorption, was similar in untreated and AMY-treated diabetic rats (35.0+/-3.1 vs. 35.1+/-4.4 nmol/mmol creatinine), intermediate in rats treated with INS (49.9+/-2.7), and normalized in diabetic rats treated with both agents (58.8+/-8.9 vs. 63.2+/-4.5 in CONT). Thus, in our STZ rat model of diabetic osteopenia, addition of AMY improved bone indices apparently by both inhibiting resorption and stimulating bone formation.     

T3 preserves respiratory function in sepsis

Sepsis produces profound hypothyroidism. This hypothyroid state is associated with altered lung metabolism and structural integrity. We studied the respiratory function of rats during sepsis-induced hypothyroidism with or without T3 treatment. Forty-four male Holtzman rats underwent cecal ligation and puncture (CLP). Treatment was administered at six hours after surgery consisting of intraperitoneal injection of T3 (15 micrograms/kg, n = 19) or saline (n = 25). At 20 hours (Group A) or 30 hours (Group B) following CLP, respiratory drive was assessed by serial occlusion pressure technique (P0.1). The rats were killed and static elastance determined by serial air inflation to 10 cc. The lungs were excised for weight determination. The P0.1 values were significantly greater in T3-treated animals over controls in Group A (9.3 +/- 0.7 vs. 6.6 +/- 2.2, p less than 0.05 by t test); elastance was significantly improved by T3 treatment in Group B (p less than 0.05 by two-way ANOVA). Lung weight, pH, pO2, pCO2, respiratory rate (RR), and mortality were not significantly different between groups. Control animals were hypothyroid by 20 hours after CLP (T3 less than 12.5 ng/dL) whereas T3-treated animals were euthyroid (T3 = 145 +/- 43 ng/dL). Pulmonary dysfunction frequently accompanies sepsis; the euthyroid state appears protective. We found a significantly improved respiratory drive in septic animals with T3 treatment. Lung elastance was similarly improved in late sepsis with T3 treatment. The data suggest that T3 treatment preserves respiratory function in septic rats as evidenced by respiratory drive and compliance.