scholarly journals A possible role of adenylate cyclase in the longterm dietary regulation of insulin secretion from rat islets of Langerhans

1973 ◽  
Vol 136 (2) ◽  
pp. 343-349 ◽  
Author(s):  
Simon L. Howell ◽  
Irene C. Green ◽  
William Montague
Keyword(s):  
Insulin Secretion ◽  
Adenylate Cyclase ◽  
Islets Of Langerhans ◽  
Glucose Concentration ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Maximal Response ◽  
Long Term Effects ◽  
Stimulation Of

1. Adenylate cyclase activity and patterns of insulin release in response to various concentrations of glucose were determined in islets of Langerhans isolated from starving, fed, or glucose-loaded rats. 2. Basal and glucagon-stimulated activities of adenylate cyclase were lower in islets from starved than from fed rats. The minimum glucose concentration required for stimulation of insulin secretion was higher, whereas the maximum secretory response to glucose was lower, in islets from starved than from fed rats. 3. Adenylate cyclase activity in islets of Langerhans obtained from fed rats loaded with glucose by intermittent intravenous or intraperitoneal injections over 5h was significantly higher than that seen in islets from normal fed rats. Islets obtained from glucose-loaded rats required a lower glucose concentration for stimulation of insulin secretion and attained a higher maximal response to glucose stimulation than those derived from fed rats. 4. Incubation in vitro of islets isolated from normal fed rats, for periods of 1 to 24h in the presence of high concentrations of glucose resulted in an activation of adenylate cyclase that occurred progressively from 2 to 7h and which was maintained during 24h of incubation. The increase of adenylate cyclase activity in isolated islets incubated for 4h in the presence of glucose was not prevented by addition of cycloheximide or actinomycin D. Galactose or 2-deoxyglucose was ineffective in increasing adenylate cyclase activity, and pyruvate (20mm) was less effective than glucose. 5. It is suggested that glucose or a glucose metabolite may exert long-term effects on islet cell adenylate cyclase.

Stimulation of Adenylate Cyclase Activity in Rat Thymocytes in Vitro by 3,5,3′-Triiodothyronine*

Endocrinology ◽  
1985 ◽  
Vol 116 (5) ◽  
pp. 2036-2043 ◽  
Author(s):  
JOSEPH SEGAL ◽  
CHRISTOPHER BUCKLEY ◽  
SIDNEY H. INGBAR
Keyword(s):  
Adenylate Cyclase ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Stimulation Of

Antisecretory effects of berberine in rat ileum

1981 ◽  
Vol 241 (3) ◽  
pp. G253-G258 ◽  
Author(s):  
Y. H. Tai ◽  
J. F. Feser ◽  
W. G. Marnane ◽  
J. F. Desjeux
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Rat Ileum ◽  
Ion Secretion ◽  
Stimulation Of

The in vitro antisecretory effects of the alkaloid berberine (1.0 mM) on intestinal ion secretion and mucosal adenylate cyclase and Na-K-ATPase activities were studied in the rat ileum. Mucosal berberine did not alter the individual basal net ion fluxes and basal adenylate cyclase activity but decreased short-circuit current (Isc) and increased the net absorption of chloride plus bicarbonate. In the cholera toxin-treated tissue, mucosal berberine stimulated absorption of Na and Cl and inhibited the increased adenylate cyclase activity but did not change the specific Na-K-ATPase activity, whereas serosal berberine stimulated Na secretion and decreased Isc. Mucosal berberine also decreased Isc, increased Cl permeability, and reversed the ion secretion induced by dibutyryl cyclic AMP, the heat-stable enterotoxin of Escherichia coli, and methylprednisolone administration. The antisecretory effects of mucosal berberine may be explained by stimulation of a Na-Cl-coupled absorptive transport process. The mechanism of action of serosal berberine remains to be elucidated. However, it is clear that mucosal berberine affects intestinal ion transport by mechanisms different from stimulation of the Na pump and probably at a step distal to the production or degradation of cyclic AMP or cyclic GMP.

Stimulation of insulin secretion from isolated rat islets of Langerhans by melittin

1984 ◽  
Vol 4 (8) ◽  
pp. 665-671 ◽  
Author(s):  
Noel G. Morgan ◽  
William Montague
Keyword(s):  
Insulin Secretion ◽  
Islets Of Langerhans ◽  
Maximal Response ◽  
Secretory Rate ◽  
Rat Islets ◽  
Cell Plasma ◽  
Rat Islets Of Langerhans ◽  
Dose Dependent ◽  
Stimulation Of

Melittin, an amphipathic polypeptide, stimulated the secretion of insulin from rat islets of Langerhans incubated in vitro. The secretory response was dose-dependent and saturable with half the maximal response elicited by a melittin concentration of 4 μg/ml. The response was rapid in onset, an increase in secretion occurring within 2 rain of exposure of the islets to melittin (2 μg/ml). An enhanced secretory rate could be maintained for at least 40 rain in the presence of melittin but declined steadily when the agent was removed. Stimulation of secretion by melittin occurred in the absence of glucose and in the presence of both 4 mM and 8 mM glucose but not in the presence of 20 mM glucose. The effect of melittin on secretion was dependent on the presence of extracellular calcium but was not inhibited by norepinephrine. The data suggest that melittin may be a valuable agent for further study of the role played by the B-cell plasma membrane in the regulation of insulin secretion.

scholarly journals Adenosine and the regulation of insulin secretion by isolated rat islets of Langerhans

1977 ◽  
Vol 164 (2) ◽  
pp. 409-413 ◽  
Author(s):  
N A Ismail ◽  
E E S M El Denshary ◽  
W Montague
Keyword(s):  
Insulin Secretion ◽  
Adenylate Cyclase ◽  
Beta Cell ◽  
Prostaglandin E2 ◽  
Islets Of Langerhans ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Rat Islets ◽  
Adrenergic Blocker ◽  
Rat Islets Of Langerhans

The effect of adenosine in insulin secretion and adenylate cyclase activity of rat islets of Langerhans was investigated. Adenosine inhibited insulin secretion stimulated by glucose, glucagon, prostaglandin E2, tolbutamine and theophylline. Adenosine decreased basal adenylate cyclase activity of the islets as well as that stimulated by glucagon prostaglandin E2 and GTP, although fluoride-stimulated activity was not affected. Neither insulin secretion nor adenylate cyclase activity of the islets was affected by adenine, AMP or ADP. The inhibitory effect of adenosine on adenylate cyclase activity was not altered by either phenoxybenzamine (alpha-adrenergic blocker) or propranolol (beta-adrenergic blocker), suggesting that the effect is not mediated through the adrenergic receptors of the islet cells. These results suggest that the intracellular concentration of adenosine in the beta-cell may play a role in regulating insulin secretion and that this effect may be mediated via alterations in the activity of adenylate cyclase in the beta-cell.

scholarly journals Regulation of GH3 pituitary tumour-cell adenylate cyclase activity by activators of protein kinase C

1989 ◽  
Vol 262 (3) ◽  
pp. 829-834 ◽  
Author(s):  
L A Quilliam ◽  
P R M Dobson ◽  
B L Brown
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Maximal Response ◽  
Kinase C ◽  
Cyclic Amp Accumulation ◽  
Stimulation Of

The influence of protein kinase C (PKC) activation on cyclic AMP production in GH3 cells has been studied. The stimulation of cyclic AMP accumulation induced by forskolin and cholera toxin was potentiated by 4 beta-phorbol 12,13-dibutyrate (PDBu). Moreover, PDBu, which causes attenuation of the maximal response to vasoactive intestinal polypeptide (VIP), also induced a small right shift in the dose-response curve for VIP-induced cyclic AMP accumulation. PDBu-stimulated cyclic AMP accumulation was unaffected by pretreatment of cells with pertussis toxin or the inhibitory muscarinic agonist, oxotremorine. PDBu stimulation of adenylate cyclase activity required the presence of a cytosolic factor which appeared to translocate to the plasma membrane in response to the phorbol ester. The diacylglycerol-generating agents thyroliberin, bombesin and bacterial phospholipase C each stimulated cyclic AMP accumulation, but, unlike PDBu, did not attenuate the stimulation induced by VIP. These results suggest that PKC affects at least two components of the adenylate cyclase complex. Stimulation of cyclic AMP accumulation is probably due to modification of the catalytic subunit, whereas attenuation of VIP-stimulated cyclic AMP accumulation appears to be due to the phosphorylation of a different site, which may be the VIP receptor.

Cytochemical Evidence for Presynatic β-Adrenergic Regulation of Secretion in the Developing Rat Submandibular Gland

1977 ◽  
Vol 35 ◽  
pp. 430-431
Author(s):  
L.S. Cutler
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Submandibular Gland ◽  
Neonatal Rat ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Parotid Glands ◽  
Adrenergic Agonist ◽  
Rat Submandibular Gland

Many studies previously have shown that the B-adrenergic agonist isoproterenol and the a-adrenergic agonist norepinephrine will stimulate secretion by the adult rat submandibular (SMG) and parotid glands. Recent data from several laboratories indicates that adrenergic agonists bind to specific receptors on the secretory cell surface and stimulate membrane associated adenylate cyclase activity which generates cyclic AMP. The production of cyclic AMP apparently initiates a cascade of events which culminates in exocytosis. During recent studies in our laboratory it was observed that the adenylate cyclase activity in plasma membrane fractions derived from the prenatal and early neonatal rat submandibular gland was retractile to stimulation by isoproterenol but was stimulated by norepinephrine. In addition, in vitro secretion studies indicated that these prenatal and neonatal glands would not secrete peroxidase in response to isoproterenol but would secrete in response to norepinephrine. In contrast to these in vitro observations, it has been shown that the injection of isoproterenol into the living newborn rat results in secretion of peroxidase by the SMG (1).

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