Secretory component and lactoferrin in pure pancreatic juice in chronic pancreatitis

To evaluate pathophysiological roles of proteins in pancreatic secretion, immunoreactive lactoferrin (LF) and secretory component (SC) were measured in the first fraction of the pure pancreatic juice obtained endoscopically from 17 control, 21 suspected (SCP), 14 noncalcified (NCP), and 14 calcified chronic pancreatitis (CCP) subjects. The protein and amylase tended to decrease both in concentration and output from control to CCP. LF concentration was elevated in CCP (18.0±4.9/ml) when compared with controls (2.3±0.2g/ml), and LF output in NCP (12.3±3.8 g/min) was increased from controls (3.8±0.6 g/min). The combination of high LF concentration with low protein output was observed in 10/14 in CCP but 0/14 in NCP and can be a biochemical discriminator of CCP from NCP. SC concentrations were also elevated in NCP (8.5±2.0 g/ml) and CCP (5.6±1.6 g/ml) from controls (1.2±0.2 g/ml). SC outputs in SCP (9.8±3.1 g/min) and NCP (21.1±4.8 g/min) were increased from controls (1.7±0.3 g/min), but there was no further increase in CCP. Hypersecretion of LF and SC in chronic pancreatitis is different, especially in CCP, although the mechanisms for hypersecretion are unknown.This study was supported in part by a research grant for intractable pancreatic disease from the Ministry of Health and Welfare, Japan.     

Esophageal carcinoma in house musk shrews,Suncus murinus (insectivora), induced by N-methyl-N′-nitro-N-nitrosoguanidine

Female 6-week-old shrews were given a solution ofN-methyl-N-nitroN-nitrosoguanidine (MNNG) at a concentration of 50 g/ml or 100 g/ml in the drinking water. All 11 shrews receiving 100 g/ml MNNG died 8–13 days after the beginning of carcinogen administration and 6 of the 20 shrews receiving 50 g/ml MNNG died after 10–54 days. When animals were between 43 and 54 weeks of age, multiple esophageal lesions were evoked in all 14 that had received 50 g/ml MNNG for 30 weeks. All shrews developed a protruding, ulcerative, or superficial type of squamous-cell carcinoma of the esophagus, accompanied by papillomas. Local invasion was seen in squamous-cell carcinoma but no distant metastasis was noted. None of the 5 control shrews developed any esophageal abnormality. No gastric adenocarcinoma, intestinal sarcoma, or other tumors were induced with MNNG. It can be concluded that MNNG has a carcinogenic effect on shrew esophageal epithelium.Abbreviations MNNG N-methyl-N-nitro-N-nitrosoguanidine - ENNG N-ethyl-N-nitro-N-nitrosoguanidine - BrdU 5-bromo-2-deoxyuridine     

Aqueous extract of betel-nut of North-East India induces DNA-strand breaks and enhances rate of cell proliferation in vitro

Summary An aqueous extract of betel-nut has been found to be able to induce strand breaks in DNA of mouse kidney cells in vitro. It has been also found to be able to enhance the rate of cell division at a dose of 100 g/ml while a higher dose of 250 g/ml was extremely toxic to the cells. Compared with arecoline (10 g/ml), the aqueous extract of betel-nut seems to be a more potent carcinogen to mouse kidney cells in vitro.Financial support for this work has been received from D.O.E. under Himalayan Eco-Development Project, N.E.H.U. (Eco-Dev/85/6)     

Alterations in the heart sarcolemmal Ca2+ transport activity by some β-adrenergic antagonists

Summary The effects of some -adrenergic antagonists such as acebutolol, propranolol, pindolol and oxprenolol (1–1000 M) were studied on the rat heart sarcolemmal Ca²⁺ transport activities. Pindolol enhanced sarcolemmal ATP-dependent Ca²⁺ binding and Ca²⁺-stimulated ATPase whereas acebutolol had no effect. Both propranolol and oxprenolol had biphasic actions on the sarcolemmal Ca²⁺ pump activities; the lower concentrations (1 and 10 M) were stimulatory, but the higher concentrations (100 and 1000 M) were inhibitory. None of the drugs used in this study had any effect on Mg²⁺ ATPase and non-specific Ca²⁺ binding activities of heart sarcolemma except that 1000 M propranolol decreased Mg²⁺ ATPase activity significantly. Mitochondrial and microsomal ATP-dependent Ca²⁺ binding activities were unaffected by these drugs (1–1000 M), except that 1000 M propranolol was inhibitory. These results suggest differences among various -adrenergic blocking drugs with respect to their actions on sarcolemmal Ca²⁺ pump in the myocardium.     

Central and peripheral serotonergic influences on viscerovisceral inhibitory reflex during duodenal distension in sheep

The effects of duodenal distension on forestomach and abomasal motility were investigated in conscious sheep chronically fitted with intraparietal electrodes, a duodenal cannula, and an intracerebroventricular cannula. Duodenal distensions with a balloon inflated with 40 ml (DD40) of water reduced the frequency of forestomach and abomasal contractions by 45 and 32%, respectively, while distension with 80 ml (DD80) induced a total inhibition. Methysergide, a mixed 5HT₁-5HT₂ antagonist administered intravenously (200 g/kg) or intracerebroventricularly (20 g/kg) suppressed the DD40-induced inhibition and reduced that induced by DD80. Sprioxatrine, a selective 5HT_1A antagonist, intravenously (100 g/kg) or intracerebroventricularly (10 g/kg), suppressed the DD40 and DD80-induced inhibition, which was also attenuated by the 5HT₂ antagonist ritanserin given intravenously (200 g/kg) or intracerebroventricularly (20 g/kg). Granisetron, a 5HT₃ antagonist, injected intravenously (150 g/kg), abolished the effects of DD40 and DD80 while it had no antagonistic action on DD40 and DD80 when given intracerebroventricularly (15 g/kg). It is concluded that in sheep, duodenal distension inhibits forestomach and abomasal motility through 5HT_1A and 5HT₂ receptors at the level of the central nervous system and 5HT₃ receptors located peripherally.This work was presented in part at the First United European Gastroenterology Week, September 25–30, 1992, Athens, Greece.     

Granulocyte elastase in assessment of severity of acute pancreatitis

Complexes of granulocyte elastase and ₁-antitrypsin are markers for granulocyte activation. In 75 patients with acute pancreatitis these complexes were immunologically determined daily in plasma during the first week of hospitalization. Patients were classified into three groups: mild pancreatitis (I, 1 complication, N=34), severe pancreatitis (II, 2 complications, N= 29), lethal outcome (III, N=12). Initially, granulocyte elastase (mean±sem) was lower in group I (348±39 g/liter) as compared to groups II (897±183 g/l) and III (799±244 g/liter), P<0.001 for I vs II + III. Initial elastase concentrations >400 g/liter were consistent with a severe or fatal course of the disease but did not distinguish between severe and lethal pancreatitis. In patients with mild or severe disease, mean elastase concentrations decreased continuously during the following days (197±15 g/liter in mild cases, 325±30 g/liter in severe cases at day 7). In patients with lethal disease, however, mean elastase concentrations even increased at day 2 and remained higher than 700 g/liter during the observation period. At days 1 and 2 the predictive value for severe or lethal disease of raised (>400 g/liter) elastase concentrations [positive predictive value (PPV) 82%, negative predictive value (NPV) 81%] was better than that of elevated (>100 mg/liter) C-reactive protein (PPV 73%, NPV 73%), elevated (>4.0 g/liter) ₁-antitrypsin (PPV 59%, NPV 50%), or decreased (<1.5 g/liter) ₂-macroglobulin (PPV 82%, NPV 67%). When the time course of the concentrations of the acute-phase proteins was studied, it was found that rises of granulocyte elastase were followed by elevated C-reactive protein levels after one day, by elevated ₁-antitrypsin levels after two days and by decreased ₂-macroglobulin levels after three to four days. We conclude that granulocyte elastase is a good early marker for the severity of acute pancreatitis. Compared with elevated levels of C-reactive protein and ₁-antitrypsin release of granulocyte elastase reflects an event that precedes acute-phase protein induction.     

C-reactive protein (CRP) levels in systemic lupus erythematosus (SLE)

Summary CRP levels in 194 serum samples from 43 SLE patients were measured. Patients with inactive disease have levels below 10 g/ml; patients with active SLE have higher levels, but never over 50 g/ml. In the presence of infection or inflammatory processes, regardless of the activity of SLE, the levels are significantly higher (p<0.05), and well over 50 g/ml. Both active SLE patients and inactive SLE patients with local infections have levels between 10 g/ml and 50 g/ml. In this situation, the presence of anti-DNA antibodies strongly suggests disease activity (82% versus 9%, p<0.05). The clinical and physiopathological meaning of these findings is discussed.     

Deleterious effects of digitalis on reperfusion-induced arrhythmias and myocardial injury in ischemic rat hearts: possible involvements of myocardial Na+ and Ca2+ imbalance

Summary Isolated rat hearts were made ischemic for 25 min after an initial recirculating perfusion, followed by 30 min of reperfusion. In some hearts, interventions including administration of ouabain and/or high [K⁺] in the buffer were performed during the first 10 min of reperfusion.During ischemia, intracellular Na⁺ (Na_i) increased from 15 to 64 [mol/g dry weight (dwt). During reperfusion, Na_i declined rapidly (at 10 min of reperfusion: 48 nol/g dwt, at 30 min: 25 mol/g dwt) and regular rhythm was recovered within 10 min in hearts without any intervention during reperfusion.⁴⁵Ca²⁺ uptake increased from 0.8 to 7.5 mol/g dwt after 30 min of reperfusion. Ventricular function recovered by 45 %.A 10-min perfusion with 10 or 50 M of ouabain increased Na_i (17 to 21 or 27 mol/g dwt) with increased left-ventricular (LV) contractile function, but these effects were reversed by combination of high perfusate [K⁺] (20 mM) in non-ischemic hearts.A 10-min reperfusion with ouabain retarded or stopped the decline in Na_i (at 10 min of reperfusion: 54 or 63 mol/g dwt, at 30 min: 32 or 40 mol/g dwt). These amounts of ouabain also increased the incidence of ventricular tachyarrhythmias during reperfusion to 30 % or 50 %, and increased the duration of ventricular fibrillation from 6.5 to 11.5 or 18.0 min.⁴⁵Ca²⁺ uptake reached to 8.8 or 10.0 mol/g dwt, and function recovered only 35 % or 28 %. When high perfusate [K⁺] was combined with ouabain during reperfusion, the retarded decline in Nai, augmented⁴⁵Ca²⁺ uptake, and reduced recovery of function caused by ouabain alone were attenuated. These results suggest that digitalis has toxic effects on reperfused ischemic hearts by inhibition of rapid active outward transport of previously elevated Na_i and potentiation of Ca²⁺ overload.The work was supported in part by grant HL 37936 from the National Heart, Lung and Blood Institute. J. R. Neely was deceased on November 29, 1988     

A sensitive double antibody radioimmunoassay for Human Growth hormone (HGH): levels of serum HGH following rapid tolbutamide infusion

Summary A double antibody radio-immunoassay for human growth hormone is described. — The assay can detect 0.0625 mg HGH/ml serum and has good reproducibility. It was found that: 1. a highly pure labelled hormone; 2. a specific and very potent guinea pig antihuman growth hormone antibody; and 3. at least five days of incubation for the first reaction were necessary to achieve this accuracy and sensitivity. -Porcine and rat growth hormone, sera from cow, guinea pig, rabbit, mouse, and toad fish did not react with the guinea pig anti-HGH serum used in the assay. — In four patients after hypophysectomy, HGH concentrations disappeared almost completely, and in another patient no rise of the hormone was seen during an IV insulin tolerance test.-Undiluted human serum appears to produce falsely high levels of HGH. — Normal males exhibited fasting HGH levels from 0 –2.2 mg/ml (mean 0.8 mg/ml). Females ranged from 0.6–15.0 mg/ml (mean 5.1 mg/ml) and 15 acromegalics from 8.0–103.0mg/ml (mean 31.2 mg/ml). — During a rapid tolbutamide tolerance test, serum HGH rose between 2.5- and 82-fold over the fasting levels within 10 to 70 minutes following the glucose nadir.Performed in part during a postdoctoral fellowship Stiftung Volkswagenwerk, Germany.     

The effects of parabiosis on serum and kidney glycosidase activities in spontaneously diabetic mice

Summary Spontaneously diabetic non-obese mice of the ICR strain were newly inbred in Shionogi laboratory, Japan. Animals became diabetic suddenly, more frequently and severely in females. Blood glucose levels were 452±73 mg/100 ml with serum insulin levels of < 1.0 U/ml in the fed state. Parabiosis with normal control ICR mice for 2 weeks decreased the blood glucose level to 260±51 mg/ 100ml (P<0.01) and resulted in serum insulin levels of 46.0±18.0 U/ml (P<0.01). Kidney homogenate -N-acetylglucosaminidase and -galactosidase activities were reduced in diabetic mice (42% and 44% decrease respectively) (P<0.025 and P<0.001), and restored almost to normal after 2 weeks of parabiosis. Renal -mannosidase activity was decreased 43% (P<0.001) in the diabetic mice but unaffected by parabiosis. Serum -N-acetylglucosaminidase, -galactosidase and -glucosidase activities were significantly increased in diabetic mice (179%; 233% and 58% increase respectively) (P<0.005, P<0.001 and P<0.001), and returned to normal with parabiosis.     

α2-Adrenergic stimulation counteracts glucose-induced rise of sodium in pancreatic islets exposed to ouabain

The effects of ₂-adrenergenic activation by clonidine on sodium handling were analysed in beta-cell-rich pancreatic mouse islets. In the steady-state situation, clonidine (1 M) amplified lowering of sodium induced by 20 mM glucose, while the content remained unchanged in 3 mM glucose. The loss of sodium in Na⁺-deficient medium was stimulated by glucose but was not affected by clonidine. This agonist also did not influence the ouabain-induced uptake of sodium at 3 mM glucose but partially counteracted additional uptake in response to 20 mM glucose. Although lacking effects of its own, 5 M yohimbine completely counteracted the action of clonidine. The glucose amplification of the ouabain-induced uptake of sodium was suppressed also by 10 M of the Ca²⁺-channel blockers methoxyverapamil and diltiazem. Both tolbutamide (100 M) and dibutyryl cyclic AMP (1 mM) mimicked the action of glucose by promoting clonidine-sensitive uptake of sodium in the presence of ouabain. It is concluded that activation of ₂-adrenoceptors has profound effects on the sodium handling of pancreatic beta-cells exposed to glucose and other stimulators of insulin release.     

A Three-dimensional Analysis of Blood Vessels in Bronchioloalveolar Carcinoma

The three-dimensional architecture of blood vessels within lung adenocarcinomas has not been well studied. In 19 cases with bronchioloalveolar carcinoma with central fibrosis, we three-dimensionally examined blood vessel architecture in 150 m thick sections stained with elastin staining and anti-CD34 antibody. We examined four regions: normal alveoli and three regions within the tumor including an area adjacent to the normal alveoli (external area), an area in which tumor cells were replacing epithelial cells (replacement area), and a central fibrotic area (fibrotic area). Elastin staining showed that elastic fibers formed the framework of the alveoli, and the alveolar structure shrank more strongly to the center of the tumor due to folding of alveolar walls invaded by adenocarcinoma cells. We also measured three vessel parameters in these four regions. The vessel diameters were 4.08±1.10 m, 3.95±1.02 m, 5.04±1.56 m, and 6.11±2.23 m, the circumferences of those vessels seen as complete circles were 43.11±12.78 m, 43.71±12.87 m, 95.21±39.32 m, and 126.77±54.65 m; the lengths between vessel bifurcations were 13.28±3.08 m, 13.47±4.58 m, 24.91±9.66 m, and 41.82±28.08 m in the normal alveoli, and the external, replacement, and fibrotic areas, respectively. Blood vessel architecture changed such that the vessels became larger and coarser towards the center of the tumor. Our three-dimensional analysis suggests continuous remodeling of alveolar capillaries rather than angiogenesis within bronchioloalveolar carcinoma.     

Ergonovine-induced constrictions of epicardial coronary arteries in conscious dogs: α-adrenoceptors are not involved

Summary The effect of i.v. ergonovine tartrate infusions (0.05–20 g/kg/min, 12 minutes duration) on coronary arteries was studied in 14 conscious dogs instrumented to continuously measure vascular diameter by an ultrasonic dimension gauge using 10-MHz piezoelectric crystals.Ergonovine induced a biphasic coronary response: small, transient dilation during the first minutes of infusion, followed by slowly developing constriction reaching its maximum 5 to 15 minutes after the end of the infusion and persisting at this level for at least 10 minutes. The threshold dosage for significant constriction was 0.05 g/kg/min. A dosage of 5 g/kg/min (cumulative 60 g/kg, corresponding to 35 g/kg ergonovine maleate) caused a decline in mean left circumflex artery diameter by 137±15 m (=4.6%) without significantly altering heart rate, plasma catecholamines or plasma renin activity. Coronary venous O₂ saturation did not decline, indicating the absence of coronary resistance vessel constriction. The epicardial artery constriction was not attenuated by a vasopressin antagonist. Under adrenergic blockade (2 mg/kg phentolamine and 2 mg/kg nadolol) or under ganglionic blockade (5 mg/kg pentolinium tartrate), ergonovine (5 g/kg/min) caused substantial elevation in mean arterial pressure, while the decline in coronary artery diameter was attenuated. When this increase in arterial pressure was prevented by appropriate bleeding, the ergonovine-induced coronary constriction was not diminished by adrenergic or ganglionic blockade. The serotonin antagonist methysergide (0.5 mg/kg) completely abolished the ergonovine-induced coronary artery vasomotion.It is concluded that ergonovine in dogs causes an epicardial coronary artery constriction comparable to the diffuse coronary artery narrowing in men not suffering from variant angina pectoris. These constrictions are not mediated by an adrenergic mechanism.Supported by Deutsche Forschungsgemeinschaft. Dedicated to Prof. Dr. A. Fleckenstein on the occasion of his 65th birthday.     

Coronary heart disease and urinary albumin excretion rate in Type 2 (non-insulin-dependent) diabetic patients

Summary Associations between overnight urinary albumin excretion rate and prevalent coronary heart disease and its major risk factors were examined in a cross-sectional study of 141 Type 2 (non-insulin-dependent) diabetic patients. Mean albumin excretion rate was higher in men (geometric mean 13.5 g/min; 95% confidence interval 10.3–17.6) than women (7.5 g/min; 5.7–9.8, p<0.01). In diabetic men and women mean albumin excretion rate was higher in those with electrocardiographic and/or symptomatic evidence of coronary heart disease than in those without (men, 23.1 g/ min; 95% confidence interval 13.7–39.0 versus 10.6 g/min; 7.9–14.2, p<0.01, women, 13.7 g/min; 8.0–23.5 versus 5.4 g/min; 4.2–6.8, p<0.01). Multiple logistic regression analysis was used to allow for confounding between variables. In the diabetic group as a whole, raised albumin excretion rate (p<0.001), gender (p<0.05) and systolic blood pressure (p=0.06) entered the best model for coronary heart disease prediction. In women, albumin excretion rate alone (p<0.01) and in men albumin excretion rate (p<0.01) and age (p=0.05) entered the best models. We conclude that albumin excretion rate is significantly associated with coronary heart disease morbidity after taking into account the confounding effects of raised blood pressure and other cardiovascular risk factors.     

Dose/response study of the effects of oestrogens on tumour growth and morphology in the Dunning R3327 prostatic adenocarcinoma

Summary The present study was undertaken to investigate to what extent the oestrogen-induced effects on growth and morphology of the Dunning R3327 rat prostatic adenocarcinoma are dose-dependent. Castrated and testosterone-supplemented rats were used in order to study effects of increasing doses of oestrogens on the tumour. It was found that the lowest dose of oestradiol-17 that reduced the overall growth, the volume density of the epithelium and epithelial cell area in Dunning R3327 prostatic tumours is 10 g given as daily injections. Higher oestrogen doses (50 g, 200 g, and 500 g), in addition to reducing the volume of tumour epithelium, also induced an increase of the volume density of tumour stroma. The area of stroma cell nuclei was increased by 50 g and 200 g oestradiol-17. These observation, may indicate that the lowest effective oestrogen dose is different in the epithelium and stroma of Dunning tumours and that large doses of oestrogen stimulate the stromal compartment. This stimulatory effect did not influence the inhibitory effects seen on the overall growth of the tumour and on the tumor epithelium.     

Effects of two cholecystokinin variants,CCK-39 and CCK-8, on basal and stimulated insulin secretion

Summary The effects of two different cholecystokinin variants, CCK-39 and the carboxyl-terminal octapeptide CCK-8, on basal and stimulated insulin secretion were studied in the mouse. It was found that both peptides had a dose-dependent stimulating action on insulin secretion with a maximal response of similar magnitude at a dose level of about 5 nmol/kg body weight. This dose induced an increase of plasma concentrations of immunoreactive insulin of about 100 U/ml. The calculated half-maximal dose was 2.12 nmol/kg for CCK-39 and 3.18 nmol/kg for CCK-8. The insulin-secretory response to CCK-39 and CCK-8 in the absence of other secretagogues was partially abolished by pretreatment with the cholinergic blocker methylatropine as well as with the -adrenoceptor blocker L-propranolol. Thus, this great insulin-secretory response to the two peptides seemed to be dependent on intact muscarinic and -adrenergic receptors. CCK-39 or CCK-8 administered in a threshold dose prior to half-maximal doses of D-glucose, the cholinergic agonist carbachol, or the -adrenergic agonist L-isopropylnoradrenaline (L-IPNA), respectively, displayed different influences on insulin release. CCK-39 potentiated glucose- as well as carbachol-induced insulin secretion, whereas it did not influence L-IPNA-induced insulin release. An equimolar dose of CCK-8, on the contrary, had no apparent effect on either glucose-, carbachol-, or L-IPNA-induced insulin release. This observation indicates that stimulated insulin release is influenced by amino acid sequences other than those of the C-terminal octapeptide in CCK-39 and that the response of the stimulated insulin-secreting cells to CCK-39 is dependent on the nature of the secretagogue.     

Klinisch-chemische Ultramikromethoden

Zusammenfassung Es werden Probleme und Möglichkeiten bei Arbeiten im Größenordnungsbereich von Mikrolitern (1 l=0.001 ml) dargestellt und eine Grundausrüstung beschrieben, welche es gestattet, klinisch-chemische Analysen ausgehend von kleinsten Probenmengen (5–20 l) einfach, rasch und zuverlässig auszuführen. Die Arbeitsweise von halbautomatischen Pipettenflaschen, einer Ultramikrobürette, eines speziellen Spektro-Kolorimeters und anderer apparativer Hilfsmittel wird dargestellt.

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Summary The problems and practicability of working with microliters (1 l=0.001 ml.) are presented. A basic apparatus is described, which permits the simple, rapid and reliable clinical-chemical analysis of very small samples (5–20 l.). Directions are given for the operation of semiautomatic pipettes, an ultramicroburette, a special spectrocolorimeter and other auxilliary apparatus.

     

Age-related Variations in the Neuroendocrine Control,More Than Impaired Receptor Sensitivity,Cause The Reduction in the GH-releasing Activity of GHRPs in Human Aging

The mechanisms underlying the reduction in the GH-releasing activity of GHRPs in aging are still unclear. Aim of our study was to verify in man whether age-related impairment of the neurohormonal control of GH secretion and/or receptor alterations are involved in the reduced GH response to GHRPs in aging. To this goal, in 16 normal elderly subjects (E, 66–81 yr) and 12 young controls (Y, 24–28 yr) we studied the effects of 1.0, 2.0 and 3.0 g/kg iv Hexarelin (HEX), a synthetic hexapeptide, or GHRH, as well as the interaction among HEX (2.0 g/kg), GHRH (2.0 g/kg) and arginine (ARG, 0.5 gr/kg) on GH secretion. In Y the GH response to increasing doses of HEX (1.0 vs. 2.0 vs. 3.0 g/kg; AUC0;v–120 ± SEM: 1728.4 ± 406.4 vs. 2265.9 ± 298.4 vs. 2934.3 ± 482.2 g//L/h, p < 0.05 for 1.0 vs. 2.0 g/kg) and GHRH (649.6 ± 111.4 vs. 792.2 ± 117.6 vs. 1402.6 ± 363.0 g/L/h) showed a progressive increase. Two g/kg HEX and 1 g/kg GHRH were the maximal effective doses. Similarly, in E the GH response to increasing doses of HEX (336.7 ± 50.0 vs. 742.8 ± 157.9 vs. 1205.1 ± 178.1 g/L/h, p < 0.05 for 1.0 vs. 2 g/kg, p < 0.001 for 1.0 vs. 3.0 g/kg and p < 0.03 for 2.0 vs. 3.0 g/kg) and GHRH (183.8 ± 27.3 vs. 260.9 ± 17.3 vs. 356.1 ± 46.3 g/L/h, p < 0.005 for 1.0 vs. 3.0 g/kg and p < 0.05 for 2.0 vs. 3.0 g/kg) showed a progressive increase. In E the GH response to 3 g/kg HEX or GHRH were clearly higher than those to 2 g/kg. However, at each dose the GH responses to HEX or GHRH in E were lower (p < 0.05) than those in Y. In Y the GH response to HEX + GHRH was synergistical (4259.2 ± 308.0 g/L/h, p < 0.05). ARG strikingly potentiated the GHRH-induced GH rise (2640.8 ± 273.6 g/L/h, p < 0.01) but not the HEX-induced one (2371.7 ± 387.2 g/L/h) as well as the synergistical effect of HEX and GHRH (4009.1 ± 360.8 g/L/h). In E the GH response to HEX and GHRH was still synergistical (1947.7 ± 306.0 g/L/h, p < 0.05) but these responses were lower than those in young (p < 0.01). On the other hand, in E ARG restored the GH response to GHRH (1858.9 ± 172.8 g/L/h, p < 0.01) and even those to HEX (2069.5 ± 528.7 g/L/h, p < 0.01) and HEX + GHRH (4406.0 ± 1079.2 g/L/h, p < 0.05). Our present results indicate that the impairment of GHRP and GHRH receptor activity may have a role in the reduction of the somatotrope responsiveness in aging. However, the age-related reduction in the GH-releasing activity of GHRPs seems mainly dependent on age-related variations in the neural control, i.e. concomitant GHRH hypoactivity and somatostatinergic hyperactivity.     

Modulation of pacemaker activity in sheep cardiac Purkinje fibers by stimulation of β-adrenoceptor subtypes

The electrophysiological effects mediated by ₁- and ₂- in spontaneously active sheep cardiac Purkinje fibers were investigated using the non-selective agonist (–)-isoproterenol (IPN) and the selective agonists (–)-noradrenaline (₁) and procaterol (₂) in the absence and presence of the selective antagonists bisoprolol (₁) and ICI 118,551 (₂).IPN (0.01 mol/l) increased the spontaneous rate by 54% and the slope of diastolic depolarization by 68% of the respective control values. Further, IPN increased the action potential duration at –20 mV (APD –20 mV) from 96 to 154 ms, reduced the APD –70 mV by 17% and the duration of the diastole by 39% and slightly hyperpolarized the maximum diastolic potential. These effects were partially inhibited by ICI 118,551 (0.03 mol/l), diminished by bisoprolol (0.1 mol/l) and almost completely blocked by the combination of both antagonists. Concentration response curves of IPN were influenced by the selective antagonists as follows: ICI 118,551 (0.03 mol/l) shifted the curves to the right by 0.2–0.4 log units and increased the slope factor. Bisoprolol (0.1 mol/l) induced a greater shift to the right by 1.1–1.5 log units. Combination of bisoprolol with ICI 118,551 shifted the curves to the right by 1.5–1.7 log units.Noradrenaline (0.3 mol/l) elicited similar actions as IPN. Bisoprolol (0.1 mol/l) shifted the concentration response curves of noradrenaline to the right by 1.1–1.9 log units. Actions of procaterol (0.1 mol/l) were weak, attained only 15–35% of the maximal effects of IPN and could be blocked by ICI 118,551 (0.03 mol/l).These results show that the increase of pacemaker activity induced by catecholamines in sheep cardiac Purkinje fibers is predominantly mediated by stimulation of ₁. However, contribution of ₂ mediated effects could be demonstrated.Supported by Ministerium für Wissenschaft und Forschung, Nordrhein-Westfalen, Projekt-Nr, 40008786.     

Induction and activation of procollagenase in rabbit synovial fibroblasts after treatment with active oxygen released by xanthine/xanthine oxidase

Treatment of rabbit synovial fibroblasts with active oxygen (AO) released by xanthine/xanthine oxidase resulted in an induction of procollagenase in these cells in concentrations ranging from 12.5 g/ml xanthine plus 0.0025 U/ml xanthine oxidase to 50 g/ml xanthine plus 0.01 U/ml xanthine oxidase. Preceding this there was an accumulation of poly(ADP-ribose) for the same concentration range of xanthine/xanthine oxidase. Furthermore, it was found that AO caused activation of the latent procollagenase to the active enzyme in concentrations ranging from 0.1 g/ml xanthine plus 0.00002 U/ml xanthine oxidase to 1 g/ml xanthine plus 0.0002 U/ml xanthine oxidase. It is suggested that poly(ADP-ribosyl)ation participates in the induction of procollagenase by relaxing chromatin. Furthermore, it is proposed that AO activates latent procollagenase under physiological conditions.