AJP - Endocrinology and Metabolism, Vol 258, Issue 4 E643-E648, Copyright © 1990 by American Physiological Society
Effect of 1,25 dihydroxyvitamin D3 on isolated islets from vitamin D3-deprived rats
B. J. Billaudel, A. G. Faure and B. C. Sutter
Laboratoire d'Endocrinologie, Universite de Bordeaux I, Talence, France.
Insulin release is impaired by vitamin D3 deficiency but can be restored by
in vivo administration of 1,25 dihydroxyvitamin D3 [1,25(OH)2D3]. A direct
influence of 1,25(OH)2D3 on the B-cell was studied in vitro with islets
from 5-wk vitamin D3-deprived rats. This hormone (10(-12) to 10(-6) mol/l)
added to the incubation medium had a stimulatory dose-dependent effect on
insulin response to 8.3 mmol/l glucose 6 h later. Moreover, perifusion
experiments performed after different times of incubation demonstrated that
after 6 h 1,25(OH)2D3 increased in particular the first phase of insulin
response to 16.7 mmol/l glucose. The 45Ca fluxes, followed in parallel,
were never modified by 1,25(OH)2D3 in the absence of glucose but were
enhanced during the glucose stimulus, whereas 86Rb fluxes were never
affected by 1,25(OH)2D3. These results demonstrated that 1,25(OH)2D3 acts
in vitro on B-cells, but with a 6-h delay to potentiate the glucose-induced
insulin release, concomitant with intracellular calcium redistribution.
