Carbachol has opposite effects to glucose in raising the sodium content of pancreatic islets.
Integrating flame photometry was used for measuring sodium in single pancreatic islets from ob/ob mice. Exposure to 100 microM carbachol resulted in a 25-40% increase in sodium without any effect on potassium during incubation with 0-5 mM glucose in media deficient or not in Ca2+. This action of carbachol was abolished by 10 microM atropine or by raising the glucose concentration to 20 mM. A minor increase of the steady state content of sodium occurred in the presence of 200 microM ATP or 10 nM tetradecanoylphorbol 13-acetate (TPA). Carbachol differed from TPA in markedly stimulating sodium accumulation after ouabain inhibition of the Na/K pump. The results indicate that muscarinic receptor activation has opposite effects to glucose in inducing a rise of the islet content of sodium. It is suggested that the cholinergic control of the endocrine pancreas involves entry of Na+ in addition to the Na+ entry mediated by protein kinase C activation of Na+/H+ countertransport.
Saha
S
S
Department of Medical Cell Biology, University of Uppsala, Sweden.
Hellman
B
B
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D006859:Hydrogen / Q000378:metabolism; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D010783:Photometry; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001285:Atropine; D006859:Hydrogen; D000255:Adenosine Triphosphate; D002217:Carbachol; D012964:Sodium; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium