The actions of arginine and glucose on glucagon secretion are mediated by opposite effects on cytoplasmic Ca2+.
Cytoplasmic Ca2+ (Ca2+i) was monitored in single guinea-pig pancreatic alpha 2-cells exposed to modulators of glucagon release. The stimulatory amino acid arginine raised Ca2+i from 62 to 160 nM, whereas the inhibitor glucose reduced both the latter concentration and basal Ca2+i by 30%. Epinephrine which potentiates arginine-stimulated secretion by increasing cAMP, does so without affecting Ca2+i. The results indicate that glucagon secretion is positively modulated by Ca2+i. It is suggested that glucose-induced lowering of Ca2+i is a fundamental effect in cells where the sugar is readily metabolized.
Johansson
H
H
Gylfe
E
E
Hellman
B
B
D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D003593:Cytoplasm / Q000502:physiology; D004837:Epinephrine / Q000494:pharmacology; D005934:Glucagon / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*
D005934:Glucagon; D001120:Arginine; D005947:Glucose; D002118:Calcium; D004837:Epinephrine