High glucose attenuates peptide agonist-evoked increases in cytosolic free [Ca2+] in rat aortic smooth muscle cells.
Incubation of cultured rat aortic smooth muscle cells (ASMCs) in a medium containing high glucose concentrations (25 mM) did not affect the basal cytosolic free calcium ([Ca2+]i) but led to significant reductions in peak [Ca2+]i response evoked by arginine vasopressin, angiotensin II, and endothelin-1 (ET-1). This was observed in both the presence and absence of extracellular Ca2+. Maintenance of rat ASMCs in a medium containing mannose (an osmotic control for high glucose) did not affect either the basal or peptide agonist-evoked increase in [Ca2+]i. However, pretreatment with either the nonselective protein kinase C (PKC) inhibitor staurosporine or the selective PKC inhibitor 2,6-diamino-N-([1-(1-oxotridecyl)-2 piperidinyl] methyl) hexanamide reversed the attenuating effect of high glucose on peak [Ca2+]i response evoked by ET-1. Also, short-term incubation of ASMCs with the active phorbol ester, phorbol 12-myristate 13-acetate, led to a reduction in peak [Ca2+]i response to all three agonists, whereas the inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate, which does not activate PKC, had no such effect. Although high-glucose treatment of rat ASMCs led to significant reductions in the maximal number of binding sites to the extent of 39% of [125I]ET-1 specific binding, no significant differences in the affinity (Kd approximately 110 pM) characteristics were evident between control and high-glucose treatment groups. It is proposed that incubation of rat ASMCs with high glucose enhances the de novo synthesis of diacylglycerol and activates membrane-bound PKC and that this, in turn, impairs agonist-mediated intracellular Ca2+ mobilization.
Department of Pharmacology, University of Saskatchewan, Saskatoon, Canada.
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Sandirasegarane
R J
RJ
Herman
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V
Gopalakrishnan
D000470:Alkaloids / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D003470:Culture Media; D003600:Cytosol / Q000378:metabolism*; D016232:Endothelins / Q000378:metabolism / Q000494:pharmacology*; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008358:Mannose / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010880:Piperidines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D003470:Culture Media; D016232:Endothelins; D010880:Piperidines; D000804:Angiotensin II; D001127:Arginine Vasopressin; C069701:NPC 15437; D011493:Protein Kinase C; D019311:Staurosporine; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate; D008358:Mannose; D002118:Calcium