Role of calcium in suppression of glucagon release from isolated diabetic rat pancreata.
To investigate the role of extracellular Ca2+ (Ca2+) in suppression of glucagon release in diabetic animals, pancreata were isolated from streptozotocin-diabetic rats and perfused with a 15 mM glucose solution containing one of the following: (1) Ca2+ 2.1 mM and insulin 22 microU/ml, (2) Ca2+ 2.1 mM and insulin 110 microU/ml, (3) Ca2+ 2.1 mM and insulin (-) or (4) Ca2+ 0.2 mM and insulin 110 microU/ml. Although perfusion with 22 microU/ml of insulin did not alter glucagon release, perfusion with 110 microU/ml of insulin in the presence of Ca2+ and glucose significantly reduced the release of glucagon from 1.9 +/- 0.3 ng/min to 1.2 +/- 0.3 ng/min for the first 3 min. The absence of insulin enhanced glucagon release from the baseline level of 1.0 +/- 0.1 ng/min to 1.6 +/- 0.3 ng/min at 11 min and to 1.4 +/- 0.2 ng/min at 21 min. Deprivation of Ca2+ in the perfusate also enhanced glucagon release from the baseline level of 0.8 +/- 0.1 ng/min to 1.2 +/- 0.3 ng/min for the first 4 min. It is concluded that insulin suppresses glucagon release and Ca2+ is needed for the suppression of glucagon release in the presence of both insulin and glucose in streptozotocin-diabetic rat pancreata.
Fujita
Y
Y
Department of Internal Medicine, School of Medicine, Kitasato University, Sagamihara.
Kawaji
K
K
Moriya
T
T
Matoba
K
K
Ishii
K
K
Yajima
Y
Y
Okabe
H
H
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D005934:Glucagon / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
D007328:Insulin; D005934:Glucagon; D005947:Glucose; D002118:Calcium