Glucose stimulates the entry of Ca2+ into the insulin-producing beta cells but not into the glucagon-producing alpha 2 cells.
Rat pancreatic beta and alpha 2 cells were purified by autofluorescence-activated cell sorting and used for electrophysiological patch clamp studies and measurements of the initial uptake of 45Ca. Both beta and alpha 2 cells were electrically active, the action potentials of the latter cells also were detected in the absence of glucose. Furthermore, alpha 2 cells differed from beta cells in lacking a glucose-sensitive K+ channel with a single conductance of 50-60 pS (in symmetric 140 mM K+ solutions). The rate of Ca2+ entry into the alpha 2 cells was slower than that into the beta cells, being equivalent to 0.2 mmol, kg-1 dry wt min-1. Whereas raising the glucose concentration to 20 mM significantly increased the amount of Ca2+ entering the beta cells, the sugar was without effect on Ca2+ entry into the alpha 2 cells.
Wesslén
N
N
Department of Medical Cell Biology, Biomedicum, University of Uppsala, Sweden.
Pipeleers
D
D
Van de Winkel
M
M
Rorsman
P
P
Hellman
B
B
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D002469:Cell Separation; D005434:Flow Cytometry; D005934:Glucagon / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D051381:Rats
D007328:Insulin; D005934:Glucagon; D005947:Glucose; D002118:Calcium