Glucose inhibits 45Ca efflux from pancreatic beta-cells also in the absence of Na+-Ca2+ countertransport.
During perifusion with medium deprived of Ca2+, addition of glucose or omission of Na+ resulted in prompt and quantitatively similar inhibitions of 45Ca efflux from beta-cell rich pancreatic islets microdissected from ob/ob mice. Glucose had no additional inhibitory effect when Na+ was isoosmotically replaced by sucrose or choline+. When K+ was used as a substitute for Na+, the inhibitory effect of Na+ removal on 45Ca efflux became additive to that of glucose. The observation that glucose can be equally effective in inhibiting 45Ca efflux in the presence or absence of Na+ is difficult to reconcile with the postulate that the Na+-Ca2+ countertransport mechanism is a primary site of action for glucose.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008820:Mice, Obese; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
D012964:Sodium; D005947:Glucose; D002794:Choline; D011188:Potassium; D002118:Calcium