Human interleukin 1β stimulates islet insulin release by a mechanism not dependent on changes in phospholipase C and protein kinase C activities or Ca2+ handling

1989 ◽  
Vol 121 (5) ◽  
pp. 698-704 ◽  
Author(s):  
Nils Welsh ◽  
Thomas Nilsson ◽  
Anders Hallberg ◽  
Per Arkhammar ◽  
Per-Olof Berggren ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Phosphorylation ◽  
Phospholipase C ◽  
Insulin Release ◽  
Interleukin 1Β ◽  
High Concentration ◽  
Adult Rats ◽  
Kinase C ◽  
Protein Kinase C Activity

Abstract. Isolated islets from adult rats or obese hyperglycemic (ob/ob) mice were incubated with human recombinant interleukin 1β in order to study whether the acute effects of the cytokine on islet insulin release are associated with changes in islet phospholipase C activity, Ca2+ handling or protein phosphorylation. The cytokine stimulated insulin release both at low and high glucose concentrations during one hour incubations. In shortterm incubations (<1 min) interleukin 1β did not affect the production of inositoltrisphosphate. Addition of interleukin 1β affected neither the cytoplasmic free Ca2+ concentration at rest nor that observed subsequent to stimulation with a high concentration of glucose. Furthermore, the endogenous protein kinase C activity, as visualized by immunoprecipitation of a 32P-labelled substrate for this enzyme, was not altered by interleukin 1β. Separation of 32P-labelled proteins by means of 2-dimensional gel electrophoresis failed to reveal any specific effects of the cytokine on the total protein phosphorylation activity. These results suggest that the stimulatory effects on insulin release exerted by interleukin 1β are not caused by acute activation of phospholipase C and protein kinase C or by an alteration of islet Ca2+ handling of the B-cells.

Cognition stimulating drugs modulate protein kinase C activity in cerebral cortex and hippocampus of adult rats

Life Sciences ◽  
1993 ◽  
Vol 53 (24) ◽  
pp. 1821-1832 ◽  
Author(s):  
Laura Lucchi ◽  
Alessia Pascale ◽  
Fiorenzo Battaini ◽  
Stefano Govoni ◽  
Marco Trabucchi
Keyword(s):  
Cerebral Cortex ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Adult Rats ◽  
Kinase C ◽  
Protein Kinase C Activity

Trypsin stimulation of aldosterone and 18-hydroxycorticosterone production by rat adrenal zona glomerulosa tissue is mediated by activation of protein kinase C

1990 ◽  
Vol 5 (1) ◽  
pp. 85-93 ◽  
Author(s):  
G. P. Vinson ◽  
S. M. Laird ◽  
J. P. Hinson ◽  
N. Mallick ◽  
S. Marsigliante ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Polymyxin B ◽  
Zona Glomerulosa ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Tissue Sensitivity ◽  
Protein Components

ABSTRACT When rat adrenal whole capsules, containing the zona glomerulosa, were incubated, addition of the protein kinase C inhibitors TMB-8 (10 μmol/l), W7, H7, polymyxin-B and sphingosine (all 1 μmol/l) was found to inhibit the steroidogenic response to trypsin. Aldosterone and 18-hydroxycorticosterone were strongly, and corticosterone moderately, affected, while the production of 18-hydroxydeoxycorticosterone was neither stimulated by trypsin nor inhibited by the protein kinase C inhibitors. Addition of neomycin, which prevents substrate interaction with phospholipase C, also inhibited the response to trypsin, while addition of phospholipase C itself stimulated aldosterone, 18-hydroxycorticosterone and corticosterone production with the same tissue sensitivity as trypsin. Addition of phospholipase A2 had no effect. Direct assay of protein kinase C activity showed that trypsin stimulation effected the translocation of Ca2+/phospholipid-activated protein kinase C from the cytosolic to the membrane fraction. When glomerulosa tissue was incubated with [32P]ATP, and cytosolic proteins were subjected to isoelectric focusing on polyacrylimide gels, autoradiography showed that incorporation of 32P into several protein components was increased by trypsin stimulation. It was concluded that trypsin exerts its stimulatory effects on steroidogenesis by activating protein kinase C; not, however, by generating the Ca2+/phospholipid-independent fragment, but possibly by enhancing the activity of phospholipase C.

scholarly journals Glucose-induced insulin secretion from islets of fasted rats: modulation by alternate fuel and neurohumoral agonists

2000 ◽  
Vol 166 (1) ◽  
pp. 111-120 ◽  
Author(s):  
WS Zawalich ◽  
KC Zawalich
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Insulin Release ◽  
Cholinergic Stimulation ◽  
Glucose Stimulation ◽  
Kinase C ◽  
Alternate Fuel ◽  
Fasted Rats

Islets from fed and 24-h-fasted rats were studied immediately after collagenase isolation. (1) After a 24-h fast, the insulin secretory responses to 8 mM glucose measured during perifusion were reduced by more than 90% from islets of fasted donors. (2) Increasing glucose to 11 or 27.5 mM resulted in enhanced insulin secretion from islets of fasted animals. (3) Fasting did not reduce islet insulin content. (4) Responses to 8 or 27.5 mM glucose were not affected if fatty acid-free albumin was used during the perifusion. (5) Inclusion of alpha-ketoisocaproate (5 mM), monomethyl succinate (10 mM) or carbachol (10 microM) significantly amplified insulin release from fasted islets in the simultaneous presence of 8 mM glucose. (6) Phospholipase C activation by glucose, carbachol or their combination was not adversely affected by fasting. (7) The response to the protein kinase C activator, phorbol 12-myristate 13-acetate (500 nM), was reduced by about 60% after fasting. (8) Extending the fast to 48 h resulted in a severe decline in response to 11 mM glucose; however, the further addition of 10 microM carbachol still enhanced release from these islets. The results confirm that caloric restriction impairs islet sensitivity to glucose stimulation and that protein kinase C may be involved in the reduction of glucose-induced insulin release from these islets. The activation of phospholipase C by cholinergic stimulation may contribute to the maintenance of insulin secretion from calorically restricted animals. These results also demonstrate that free fatty acids are not essential for glucose to evoke secretion from isolated islets of fasted donors.

Stimulation of insulin release by vasopressin in the clonal β-cell line, HIT-T15: the role of protein kinase C

1992 ◽  
Vol 8 (2) ◽  
pp. 145-153 ◽  
Author(s):  
S. J. Hughes ◽  
A. Carpinelli ◽  
I. Niki ◽  
J. L. Nicks ◽  
S. J. H. Ashcroft
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Insulin Release ◽  
Direct Role ◽  
Single Class ◽  
Kinase C ◽  
Tetradecanoyl Phorbol Acetate ◽  
Protein Kinase C Activity ◽  
Short Term Exposure ◽  
Extracellular Glucose

ABSTRACT We have studied the effects of vasopressin and tetradecanoyl phorbol acetate (TPA) on cytosolic free Ca2+ ([Ca2+]i) and insulin release in HIT-T15 β-cells. Saturable binding of [3H] [Arg8]-vasopressin to HIT cell microsomes indicated a single class of receptors with a dissociation constant (Kd) of 2.5 nm and a total number of binding sites (Bmax) equal to 120 fmol/mg protein. [Arg8]-vasopressin (0.1–100 nm) elicited dose-dependent insulin release from HIT cells by up to 25-fold. This increase was dependent on the presence of extracellular glucose and was blocked by omission of extracellular Ca2+ or addition of verapamil. The stimulation was biphasic; a rapid but short-lived large increase in release was followed by a smaller sustained rise. Vasopressin also evoked a marked, concentration-dependent increase in [Ca2+]i which was also biphasic; an initial spike was followed by a sustained elevation. This increase also required glucose and was blocked by the absence of extracellular Ca2+ or the addition of verapamil. Pretreatment of the cells with TPA overnight to deplete protein kinase C activity did not affect the [Ca2+]i or insulin responses to vasopressin. However, short-term exposure to TPA markedly reduced glucose-induced steady-state [Ca2+]i, despite potentiating glucose-stimulated insulin release sevenfold, and blocked the [Ca2+]i increase induced by vasopressin. These inhibitory effects of TPA were absent in protein kinase C-depleted cells and were prevented by staurosporine. TPA had no significant effect on vasopressin-induced insulin release. Vasopressin did not modify the activity of ATP-sensitive K+ channels. These data indicate that vasopressin-induced insulin release is associated with a large increase in [Ca2+]i via increased Ca2+ entry and that this signal is markedly reduced by protein kinase C activation. Thus, protein kinase C does not have a direct role in vasopressin-induced insulin release. Simultaneous addition of vasopressin and TPA promotes insulin release, possibly through increased sensitivity of the secretory system to Ca2+ on activation of protein kinase C by TPA.

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