Pharmacological evidence for beta3 adrenoceptors in the control of rat gastric acid secretion

The effect of the ₃-adrenoceptor agonist BRL37344 on gastric acid secretion evoked by different secretory stimuli was investigated in anaesthetized rats with lumen-perfused stomachs in comparison with the ₂-adrenoceptor agonist clenbuterol. Intravenous injections of BRL37344 (1–10 mol/kg) and clenbuterol (0.01–1 mol/kg) dose-dependently reduced 2-deoxy-D-glucose-induced acid secretion, with BRL37344 about forty times less potent than clenbuterol. BRL37344 (0.1–3 mol/kg) inhibited pentagastrin-induced acid output, whereas clenbuterol was effective only at high doses (10–100 mol/kg). The inhibitory effect of BRL37344 on pentagastrin-induced acid secretion was not modified by the nonselective –adrenoceptor antagonist propranolol, but it was prevented by bupranolol, a ₃-adrenoceptor antagonist. Furthermore, neither BRL37344 (10 mol/kg) nor clenbuterol (100 mol/kg) modified the acid secretion induced by histamine. These data suggest that ₃ adrenoceptors have an inhibitory role in the control of rat gastric acid secretion induced by indirect stimuli.     

Comparison of gastric inhibitory polypeptide and intraduodenal or intravenous fat on gastric acid secretion from vagally innervated and denervated canine stomach

Gastric inhibitory polypeptide (GIP), given to dogs in graded doses (range 0.25–2 g/kg/hr) against a constant background stimulation with pentagastrin (4 g/kg/hr), failed to affect the acid secretion at all doses used except the largest one (2 g/kg/hr) which significantly reduced the acid secretion only from the vagally denervated portion of the stomach (Heidenhain pouch, HP) while raising plasma GIP two to three times above the levels reached with duodenal fat. GIP infused in a constant dose (1 g/kg/hr) significantly reduced the HP responses to lower (0.5–2 g/kg/hr) but not to higher (4–16 g/kg/hr) doses of pentagastrin, the kinetics of this inhibition being of competitive type. GIP was ineffective against a constant near maximal stimulation with pentagastrin (4 g/kg/hr), histamine (40 g/kg/hr), or liver extract meal, whereas fat (10 g), given intraduodenally or intravenously, was a powerful inhibitor of acid responses to these stimulants both from the innervated and denervated stomach. Plasma GIP reached similar levels with exogenous GIP and duodenal fat but remained unchanged with intravenous infusion of fat.     

B cell adrenoceptors and sulphonylurea-induced insulin release in mouse islets

Summary Interactions of tolbutamide and glibenclamide with B cell adrenoceptors have been reported. This study evaluated the possible role of such interactions in the stimulation of insulin release. Mouse islets were incubated in the presence of 10 mmol/l glucose alone or with tolbutamide (10 mol/l) or glibenclamide (0.02 mol/l). At 0.01–10 mol/l, blockers of ₂-adrenoceptors (yohimbine, idazoxan) or ₁-adrenoceptors (prazosin) had practically no effect on glucose-induced insulin release and did not affect its potentiation by sulphonylureas, except for a slight increase by 10 mol/l prazosin and idazoxan. Nonspecific -blockers (phentolamine, dihydroergotamine) increased control release at 10 mol/l, but only the latter amplified the response to tolbutamide. Blockers of -adrenoceptors were tested at 0.1–100 mol/l: propranolol (₁, ₂), metoprolol (₁) and compound ICI 118-551 (₂). They increased glucose-induced insulin release at 100 mol/l but variably altered the effect of sulphonylureas. Blockers of adrenoceptors have, thus, no effect on insulin release in vitro at therapeutic concentrations. At high concentrations, they non-specifically affect the action of sulphonylureas. We conclude that an interaction with B cell adrenoceptors is not involved in the insulinotropic action of sulphonylureas.     

Iron stores in 1359, 30- to 60-year-old Danish women: Evaluation by serum ferritin and hemoglobin

Summary Iron status, including serum (S-)ferritin and hemoglobin (Hb), was assessed in a population survey comprising 1359 nonpregnant Danish women in age cohorts of 30, 40, 50, and 60 years. S-ferritin levels were similar in 30- and 40-year-old women; they displayed a significant increase in 50-year-old women and a further significant increase in 60-year-old women. In the 30- and 40-year-old women, median S-ferritin was 38g/l, 5–95 percentile 6–135g/l; 17.2% had values < 15,g/l (i.e., depleted iron stores), 22.7% values from 15 to 30g/l (i.e., small iron stores), and 60.1% values > 30g/l (i.e., replete iron stores). In the 50-year-old women, median S-ferritin was 54g/l, 5–95 percentile 10–164g/l; 10.3% had values < 15g/l, 16.5% values from 15 to 30g/l, and 73.2% values > 30g/l. For the 60-year-old women, median S-ferritin was 84g/l, 5–95 percentile 25–249g/l; 1.6% had values < 15g/l, 8.6% values from 15 to 30g/l, and 89.8% values > 30g/l. Blood donors (n=180) had lower S-ferritin than nondonors in all age-groups (p<0.001). In the entire series, Hb levels were similar in 30- and 40-year-old women, median 137 g/l (8.5 mmol/l), 5–95 percentile 121–152 g/1 (7.5–9.4 mmol/l), and higher in 50- and 60-year-old women, median 140 g/l (8.7 mmol/l), 5–95 percentile 123-158 g/l (7.6–9.8 mmol/l) (p<0.0001). Hb values < 121 g/l (7.5 mmol/l) were observed in 3.8% of the women. Women with S-ferritin < 15 g/l (n=161) had lower Hb, median 134 g/l (8.3 mmol/l), than those with S-ferritin > 15 g/l, median 139 g/l (8.6 mmol/l) (p<0.001). Iron deficiency anemia (S-ferritin < 15 g/l and Hb < 121 g/l) was seen in 2.3% of 30- and 40-year-old women, and in 1.1% of 50- and 60-year-old women.     

Evaluation of rat insulin messenger RNA in pancreatic and extrapancreatic tissues

Summary The purpose of these studies was to determine whether insulin detected immunochemically in extrapancreatic tissues of the adult rat is synthesized in situ by quantitating mRNA in these tissues. A blot hybridization assay was utilized with cloned ³²P-proinsulin cDNA. The lower limit of detection was estimated to be 3pg. Proinsulin mRNA concentration was found to be 1000–1500 g in isolated pancreatic islets and was easily detected in total pancreatic RNA at 10–15 pg/ g. Proinsulin mRNA was quantitated in rat insulinoma cells adapted to culture at levels 150 those in normal islets. Samples of RNA (20–50 g) enriched about 50-fold for mRNA sequences by repeated oligo-deoxythymidylate chromatography were assayed. No insulin mRNA was detected in 50 g samples of RNA from brain or in 20 g samples from subsections of brain or other extrapancreatic tissues. RNA samples were undegraded as assessed by ability to stimulate protein synthesis in a cell-free system. Proinsulin mRNA from pancreas was added to brain homogenates and recovered intact. Brain RNA samples with insulin mRNA levels 1:1000 that of pancreas would be predicted to have 50–75 pg proinsulin mRNA/50 g sample assayed if present. Because none was found, brain must have a concentration <1:6,000 that of pancreas. These findings suggest that immunoassayable insulin detected in extrapancreatic tissues of the adult rat is synthesized by the pancreas.     

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.     

Stimulation of GTP hydrolysis in guinea pig bronchial membranes by mastoparan

Guanine nucleotide-binding proteins, or G proteins, play an important role in transmitting information from membrane receptors to intracellular effector systems. Activation of G proteins results in the hydrolysis of GTP, and the measurement of GTPase activity represents a means by which the role of G proteins in signal transduction can be investigated. GTPase activity of guinea pig bronchial membranes was measured as the liberation of ³²P_i from [-³²P]GTP. GTPase activity was divided into two components, one possessing a high affinity and the other a low affinity for GTP. The contribution of high- and low-affinity GTPase to total hydrolysis was dependent on Mg²⁺. In the presence of submicromolar Mg²⁺, high-affinity GTPase represented 65–80% of all activity, whereas in the presence of 26 µM Mg²⁺, all detectable hydrolysis was due to the low-affinity GTPase. High-affinity GTPase was stimulated by Mg²⁺ in the 0.15–1.1 M range (2.5-fold maximal stimulation, apparent Km for Mg²⁺ 0.31 M). Mastoparan (1–100 M) caused a concentration-dependent stimulation of high-affinity (but not low-affinity) GTPase (71 ± 13% maximal stimulation, EC₅₀ 0.38 M), suggesting that high-affinity GTPase may be due to a G protein. Carbachol (10 M) and fenoterol (10 M) had no effect on high-affinity GTP hydrolysis, suggesting that under the conditions described, GTPase activity of bronchial membranes is not activated by muscarinic or -adrenergic receptors, respectively. Offprint requests to: K. J. Rhoden     

Study of ridazolol on isolated canine and human coronary arteries

Summary Experiments were performed on isolated canine and human coronary arteries to study the alpha- and beta-adrenolytic properties of ridazolol. On canine coronary arteries precontracted with prostaglandin F₂ alpha 2 M and pretreated with phentolamine 1 M, ridazolol competitively antagonized the isoproterenol-induced relaxations, with a pA₂ value of 8.5 (7.8–9.1). Thereafter the alpha-adrenolytic activity of ridazolol was assessed on these same canine coronary vessels. Ridazolol activity was compared with that of prazosin on dose-response curves to norepinephrine in the presence of cocaine (30 M) and propranolol (3 M). Schild plots for both drugs gave straight lines, with slopes not different from unity. The pA₂ value was 7.1 (6.8–7.3) for ridazolol and 8.1 (7.9–8.4) for prazosin. In another set of experiments the alpha-adrenolytic activity of ridazolol was compared on canine and human coronary arteries. A submaximal contraction with norepinephrine (10 M) was first assessed in the presence of propranolol 3 M. The addition of ridazolol 3 M significantly decreased the norepinephrine (10 M)-induced contractions of both preparations. However, the inhibition was more pronounced on canine coronary arteries. In conclusion, ridazolol is a potent beta-adrenergic antagonist with moderate alpha-adrenolytic activity. The weaker inhibition of the norepinephrine-induced contraction observed in human preparations suggests the presence of a heteregeneous population of postjunctional alpha adrenoceptors.     

The circulating molecular weight forms of infused recombinant insulin-like growth factor-I and effects on glucose and fat metabolism in lambs

Summary We have investigated the relationship between the plasma distribution of infused recominant insulin-like growth factor-I across the insulin-like growth factor binding proteins and the resultant effects on glucose and fat metabolism. The studies were performed in 24-h fasted ram lambs which received primed constant infusions of ³H labelled glucose tracer. When isotopic equilibrium had been reached, the animals received 90-min infusions of human insulin-like growth factor-I at various doses (2.5, 20, 40 and 120 g· kg^–1·h^–1, n=3 for each dose). Total plasma insulin-like growth factor-I was significantly elevated by infusion at a rate of 40 g·kg^–1·h^–1 (from 185±14 g/l to 442±41 g/l, p<0.05) and 120g·kg^–1h^–1 (from 181±2 g/l to 953±39 g/1, p<0.005). The plasma concentrations of insulin-like growth factor-I not associated with binding proteins remained undetectable (<15 g/l) at the end of the 2.5 and 20 g·kg^–1·h^–1 doses, but were significantly elevated at the end of the 40 and 120 g·kg^–1·h^–1 infusions (to 71±14 g/l, p<0.05 and 176±55 g/l, p<0.01 respectively). The infused insulin-like growth factor-I associated primarily with 35–60 kilodalton binding proteins. Glucose kinetics were significantly altered only by the highest dose infusion, during which there was a fall in plasma glucose concentration from 3.5±0.2 mmol/l to 1.9±0.2 mmol/l (p<0.05). This was due to a 51% increase in the rate of glucose clearance. There was no significant change in the rate of glucose production. The plasma concentrations of glycerol and non-esterified fatty acid were not changed by any of the doses infused. We conclude that the hypoglycaemic action of infused recombinant insulin-like growth factor-I relates to a marked elevation of free insulin-like growth factor-I in the plasma, but that a threshold concentration of free insulin-like growth factor-I must be exceeded before this action is observed. The hypoglycaemic action of recominant insulin-like growth factor-I results primarily from an increase in glucose clearance while glucose metabolism was more sensitive than fat metabolism to infused recominant insulin-like growth factor-I. Both these actions contrast with those of insulin, and suggest that the acute metabolic effects of recombinant insulin-like growth factor-I are not mediated simply by cross-reaction with insulin receptors.     

The effect of dbcAMP on the lysolecithin induced hemolysis of calf and adult cattle erythrocytes

Summary The calf erythrocytes have an increased sensitivity against lysolecithin as compared to their adult counterparts. 10^–3M dbcAMP increases the hemolysis induced by 5g of lysolecithin in 0.15 M NaCl containing 10 mM phosphate buffer (pH 7.4). By increasing the level of phosphate buffer (75 mM) in the incubation mixture, 10^–3M dbcAMP decreases the hemolysis induced by 5g of lysolecithin. These data suggest a dual effect exerted by dbcAMP: the relatively labilizing or stabilizing effect prevails as a function of exogenous inorganic phosphate level.10-⁶M dbcAMP also has a relative protective effect against lysolecithin.The combined addition of cAMP (10^–3) and theophyllin (10^–4M) does not stabilize the membrane.By increasing the level of lysolecithin to 20g/ml the stabilizing effect of dbcAMP disappears.DbcAMP (10^–3) as well as cAMP (10^–3M) and theophyllin (10^–4M) have a minimum increasing effect on hemolysis in the absence of lysolecithin, too.

---

Abbreviations dbcAMP N⁶-20-dibutyryladenosine 35-monophosphate - cAMP cyclic 35-adenosine monophosphate     

Inhibition of basal and stimulated gastric H+ and pepsin secretion in duodenal ulcer patients by metiamide,an H-2 histamine antagonist

Metiamide was given orally in one dose of 200 mg in 23 studies in patients with duodenal ulcer, 4 in the basal state, 11 during histamine infusion, and 8 before insulin hypoglycemia stimulation. In the latter 8 patients insulin was given at another time without metiamide. In 17 studies acid secretion was suppressed by metiamide—up to 75% in the basal state, 53% after histamine, and 80% after insulin. Pepsin secretion was reduced to the same extent as H⁺ in the histamine studies but not in the basal (57%) or insulin (44%) studies, so that in the latter pepsin/acid ratios were 3-fold greater than in controls. Blood levels of metiamide were measured in 17 studies. In 10 out of 11 who showed inhibition of 40% or more, peak blood levels of metiamide were 0.45 g/ml to 1.25 g/ml. In 5 of 6 who did not show inhibition, blood levels were 0.05–0.4 g/ml; in the sixth it was 0.8 g/ml. Therefore a critical blood level for suppression of basal or stimulated secretion appears to be 0.45 g/ml.Supported by Public Health Service Grants AM09260 and AM05286; and by a Grant-in-Aid from Smith Kline & French Laboratories; Veterans Administration Hospital, Birmingham, Alabama, Research Project 3649-01.     

Intracytoplasmatische Glykogenablagerungen,lamelläre Strukturen und virus-ähnliche Einschlüsse in Mastzellentumoren des Hundes. Eine elektronenmikroskopische Untersuchung

Zusammenfassung Gefunden wurden: Bis zu 6 große Einschlüsse, welche aus Glykogenkörnchen bestehen; rundliche, bis zu 1,5 große, aus Lamellen zusammengesetzte Strukturen; virusähnliche Partikel (30–32 m), die einzeln oder zu mehreren in membranumgebenen Haufen liegen.

---

Intracytoplasmatic glycogen deposits, lamellate structures and virus-like inclusions in mast-cell tumours of dogs. An electron-microscopic study

Summary The following were encountered: inclusions measuring up to 6 and composed of glycogen grains; round structures measuring up to 1.5 , and consisting of laminae; viruslike particles (30–32 m) either occurring as single bodies or accumulations. The latter were surrounded by a single membrane.

     

Protection by nitecapone against sodium taurocholate-induced damage to cultured gastric cells

The goal of this study was to observe if nitecapone protected against taurocholate-induced damage in primary cultured rat gastric mucosal cells, as well as in a well-differentiated human gastric epithelial cell line (MKN 28). Prostaglandins were measured to analyze the protection mechanism. In primary rat gastric mucosal cell culture, nitecapone 125–250 M protected the cells significantly against damage induced by sodidum taurocholate, increasing cell viability by 31–38%. In the human gastric epithelial cell line, in which mitochondrial activity was measured as an indication of cell viability, nitecapone (62.5–250 M) protected the cells against sodium taurocholate-induced damage by 12–20%. Prostaglandin E₂, thromboxane B₂, and 6-keto-prostaglandin F₁ measurements in the primary cultured rat gastric mucosal cells showed that nitecapone (125 M and 250 M) significantly stimulated prostaglandin E₂ production (84.7% and 61.0%, respectively), and inhibited thromboxane B₂ formation (50% at 250 M), while the 6-keto-prostaglandin F₁ formation was unaffected. Nitecapone had no effect on prostaglandin E₂ production in the MKN 28 epithelial cell line. Indomethacin or aspirin, at concentrations that did not affect cell viability, antagonized the stimulative effect of nitecapone on prostaglandin E₂ formation in the primary cultured rat gastric mucosal cells. Although the prostaglandin E₂ synthesis was blocked, nitecapone still protected against cell damage induced by taurocholate. These results demonstrated the direct and efficacious protection of nitecapone on gastric cell level and suggest that the cytoprotection by nitecapone against taurocholate may not be mediated through the mechanism of stimulated synthesis of prostaglandin E₂.     

Untersuchungen zum antilipolytischen Effekt des Insulins am menschlichen Fettgewebe in vitro

Zusammenfassung Am menschlichen Fettgewebein vitro wurde die Hemmung der Lipolyse durch Insulin in glucosefreiem Medium untersucht. Als Parameter der lipolytischen Aktivität wurde die Produktion von Glycerin und freien Fettsäuren bezogen auf Gewebe-Feuchtgewicht gemessen. Die Metabolitfreisetzung durch Fettgewebsschnitte von 25 Normalpersonen betrug in glucosefreiem Medium unter basalen Bedingungen 0.57 ± 0.20 Mol Glycerin/g Gewebe-Feuchtgewicht/2 Std und 2.6 ± 0.8 Eq freie Fettsäuren/g Gewebe-Feuchtgewicht/2 Std — Die Lipolyse wurde durch Zusatz von Noradrenalin oder Adrenalin in Konzentrationen von 0.01 g/ml oder mehr stimuliert. Bei Konzentrationen von 0.1 und 1.0 g Katecholamin/ml ergaben sich submaximale Steigerungen der Metabolitfreisetzung auf rund das Doppelte des Basalwertes. Die mit beiden Hormonkonzentrationen erzielten Effekte waren nicht signifikant unterschiedlich, jedoch bei Noradrenalin signifikant größer als bei Adrenalin. — Zusatz von Insulin zum Inkubationsmedium hemmte die Lipolyse. Durch 33 E Insulin/ml wurde bei Fettgewebsschnitten von 18 Normalpersonen die basale Produktion von Glycerin auf 66 ± 21% und von freien Fettsäuren auf 67 ± 24% reduziert. Auch bei gleichzeitiger submaximaler Stimulation durch Katecholamine betrug die Hemmung der Lipolyse rund 1/3. — Die Konzentration-sabhängigkeit des Insulineffekts auf die Katecholamin-stimulierte Lipolyse wurde an Fettgewebsschnitten von 14 Normalpersonen geprüft. Eine signifikante Lipolyse-hemmung wurde mit einer Konzentration von 1.0 E Insulin/ml im Inkubationsmedium erzielt. Durch 100 E/ml wurde die durch Katecholaminzusatz bedingte Stimulation der Lipolyse aufgehoben. — Diein vitro nachweisbare hohe Insulinempfindlichkeit der Lipolyse des menschlichen Fettgewebes läßt darauf schließen, daß die Fettmobilisation auch unter physiologischen Bedingungenin vivo unabhängig vom Glucosestoffwechsel durch Insulin reguliert wird.

---

Investigations of the antilipolytic effect of insulin on human adipose tissue in vitro

Summary The antilipolytic effect of insulin on human adipose tissue was studied employing glucose-free incubation medium. The lipolytic activity was measured by the production of glycerol and free fatty acids, and calculated per g wet weight of tissue. Slices of adipose tissue, which was obtained after an overnight fast from 25 subjects selected for lack of metabolic or endocrine diseases, released 0.57 ± 0.20 moles glycerol/g tissue/2 h, and 2.6 ± 0.8 eq. free fatty acids/g tissue/2 h. — Lipolysis was increased by addition of 0.01 or more g epinephrine or norepinephrine per ml of medium, the increment produced by 0.1 or 1.0 g catecholamine/ml being about 100% of the basal rate. However, the effect of norepinephrine was significantly greater than the effect of epinephrine. — Addition of insulin to the medium inhibited lipolysis. 33 U of insulin per ml decreased the release of glycerol to 66 ± 21 % and the release of free fatty acids to 67 ± 24% of the basal rate. A reduction of lipolysis by about 1/3 was also seen when lipolysis was stimulated by 0.1 or 1.0 g catecholamine per ml. — The dose response of the insulin effect on stimulated lipolysis was studied in slices of adipose tissue from 14 normal subjects. A significant inhibition of lipolysis was demonstrated with 1.0 U of insulin per ml. The lipolytic effect of 0.1 or 1.0 g catecholamine per ml was completely inhibited by 100 U insulin per ml. — The marked insulin sensitivity of lipolysis in human adipose tissuein vitro would be in agreement with the concept, that mobilization of depot fat under physiological conditionsin vivo is regulated by insulin, independent of glucose metabolism.

---

Etude de l'effet antilipolytique de l'insuline sur le tissu adipeux humain in vitro

Résumé Les auteurs ont étudié l'effet antilipolytique de l'insuline sur le tissu adipeux humain en utilisant un milieu d'incubation ne contenant pas de glucose. L'activité lipolytique a été mesurée d'après la production de glycérol et d'acides gras libres, et calculée par g de poids humide de tissu. Des coupes de tissu adipeux obtenu à partir de 25 sujets à jeun depuis la veille au soir et n'ayant pas de maladies métaboliques ou endocriniennes, libéraient 0.57 ± 0.20 mol de glycérol/g de tissu en 2 h, et 2.6 ±0.8 Eq d'acides gras libres/g de tissu en 2 h. La lipolyse était augmentée par addition de 0.01 g ou plus d'adrénaline ou de noradrénaline par ml, l'augmentation produite par 0.1 ou 1.0 g de catécholamine/ml étant environ de 100% par rapport au taux de base. Cependant, l'effet de la noradrénaline était significativement plus grand que celui de l'adrénaline. L'addition d'insuline au milieu inhibait la lipolyse. 33 U d'insuline par ml réduisaient la libération de glycérol à 66± 21 % et la libération d'acides gras libres à 67 ± 24% du taux de base. Une réduction de la lipolyse d'environ 1/3 a été également observée quand la lipolyse était stimulée par 0.1 ou 1.0 g de catécholamine par ml. La relation effet-dose de l'insuline sur la lipolyse stimulée a été étudiée sur des coupes de tissu adipeux de 14 sujets normaux. Une inhibition significative de la lipolyse a été constatée avec 1.0 U d'insuline par ml. L'effet lipolytique de 0.1 ou 1.0 g de catécholamine par ml était complètement inhibé par 100 U d'insuline par ml. La sensibilité marquée de la lipolyse à l'insuline dans le tissu adipeux humain in vitro serait en accord avec l'idée que la mobilisation des graisses en dépôt dans les conditions physiologiques in vivo est régulée par l'insuline indépendamment du métabolisme du glucose.

     

Role of histamine H3 receptors in control of mouse intestinal motility in vivo and in vitro: comparison with alpha2-adrenoceptors

We tested drugs acting at histamine H₃ receptors in mice on the gastrointestinal transit of a charcoal meal in vivo and on neurogenic contractions of isolated ileal preparations. The agonist (R)--methylhistamine (100 mol/kg) caused a maximum 25% reduction of gastrointestinal transit, an effect mimicked by immepip (100 mol/kg) and antagonized by thioperamide (20 mol/kg) or clobenpropit (20 mol/kg). In the isolated ileum, (R)--methylhistamine (10–100 M) caused a slight, thioperamide-insensitive, reduction (maximum 15%) of electrically evoked cholinergic contractions. In comparison, the ₂-adrenoceptor agonist clonidine (0.1 mol/kg) caused a 35.2% inhibition of the gastrointestinal transit and almost completely reduced (maximum 82% at 1 M) the cholinergic contraction of the isolated ileum, both effects being antagonized by idazoxan (0.4 mol/kg and 1 M, respectively). These results suggest that histamine H₃ receptors, located outside the myenteric plexus, mediate an inhibition of the gastrointestinal transit in vivo. Conversely, the presence of ₂-adrenoceptors in the cholinergic nerve endings and their inhibitory role in the control of gastrointestinal propulsion is confirmed.     

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.     

Islet B-cell dysfunction and the time course of recovery following chronic overinsulinisation of normal rats

Summary Appropriate insulin therapy may preserve or improve islet B-cell function whereas the effects of overinsulinisation are unclear. Pancreatic islet B-cell function was therefore studied after overinsulinisation of normal rats for 4 weeks (fed blood glucose 2.2–4.5 mmol/l, controls 4.1–7.0 mmol/l). Insulin secretion was assessed by a 3-h hyperglycaemic clamp (10.0 mmol/l) performed 1, 48, and 120 h after insulin withdrawal (n=6 in each group). When the clamp was performed 1 h after insulin withdrawal, clamp insulin concentration was 1.6±0.1 g/l, compared to 9.3±1.0 g/l in control rats. The integrated area under the plasma insulin concentration curve was also significantly decreased (4.8±0.4 vs 20.3±2.2 g·l^–1·h^–1, p<0.001), but recovered to 9.4±1.0 g·l^–1·h^–1 after 48 h, and to 17.5±1.4 g·l^–1·h^–1 after 120 h. Pancreatic insulin contents were decreased at 1 h (6±1 g/g wet wt) and 48 h (54±12 g/g wet wt) but not at 120 h (221±30 g/g wet wt) after withdrawal (controls, 303±29 /g wet wt) and there was a strong relationship with pancreatic preproinsulin mRNA and the clamp insulin response. Thus, overinsulinisation with prolonged periods of low blood glucose concentrations impairs islet B-cell function, but is reversible over 5 days.     

Thin myofilament proteins in norm and heart failure I. Polymerizability of myocardial Straub actin in acute and chronic heart failure

Summary The reduced and intrinsic viscosities of myocardial Straub F-actin from the left ventricle of a practically healthy man were equal to 3.05±0.2 and 2.4±0.32 and from the right ventricle were 2.37±0.2 and 2.1±0.3 dl/g, respectively (the difference between ventricles was not significant). The average length of filaments measured by flow birefringence technique was equal to 1.3±0.04 m, the number-average length (Ln), determined by the electron microscopy was 1.4 m, the weight-average length (Lw), was 2 m and the maximal one was 5.5 m. The histograms showed that the most characteristic length was that of 0.8–1.2 m.According to the flow birefringence data canine myocardial F-actin had a length similar to that of myocardial F-actin from a practically healthy man, though its reduced and intrinsic viscosities were higher.In acute and especially chronic congestive heart failure the actin polymerizability was sharply reduced. In consequence, in acute heart failure the number-average length of F-actin filaments was decreased by 43% and in congestive heart failure by 65.7%.The characteristic length in acute heart failure shifts to the range of 0.2–0.6 m, while in congestive heart failure the range is 0.2–0.4 m. This fact can possibly explain why during preparation of actin from the pathologically changed myocardium according to the methods including purification by the cycles of polymerization-sedimentation-depolymerization, the pathologically changed actin is discarded and the normal actin remains.A definite parallel was observed between the reduction of actin polymerizability and the ability of myocardial glycerinated fiber bundles (MBGF) to generate force.We conclude that the changes of actin properties in heart failure may cause a decrease in contractibility of the myocardial contractile protein system.     

Antiproliferative activity of the non-myelotoxic antitumour agent of plant origin,Thaliblastine, on two human glioma cell lines

Summary The antiproliferative activity of the non-myelotoxic antitumour agent of plant origin, Thaliblastine, on two human glioma cell lines is described. Thaliblastine was added once one day following start of culture; proliferation was monitored over 7 days. The anti-proliferative activity of Thaliblastine was strongly dependent on concentration and time of incubation. The ID₅₀ of Thaliblastine in T406 and GW27 glioma lines was 5.1 g/ml and 8.2 g/ml (7.0 M and 11.2 M), respectively.Abbreviation TBL Thaliblastine     

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.