AJP - Endocrinology and Metabolism, Vol 253, Issue 1 E99-105, Copyright © 1987 by American Physiological Society
1,25-Dihydroxyvitamin D3 target cells in immature pancreatic islets
S. A. Clark, W. E. Stumpf, M. Sar and H. F. DeLuca
Target cells of 1,25-dihydroxyvitamin D3 were identified by autoradiography
in islets from rats of different ages. Nuclei of pancreatic islet cells
selectively concentrated 1,25-[3H]dihydroxyvitamin D3 but not
25-[3H]hydroxyvitamin D3 or 24,25-[3H]dihydroxyvitamin D3. Developmental
studies of pancreatic islets indicated that target cells, as revealed by
significant nuclear concentration of 1,25-[3H]dihydroxyvitamin D3, are
present in islet cells of fetal rats. The percentage of islet cells that
concentrated 1,25-[3H]dihydroxyvitamin D3 increased from 10 to 15% in the
fetus to 60% at 1 day of age. Immunocytochemical staining indicated that
insulin-containing cells but not glucagon or somatostatin cells
concentrated 1,25-[3H]dihydroxyvitamin D3. Peak uptake of
1,25-[3H]dihydroxyvitamin D3 was calculated to be 400 pmol/mg DNA, with no
significant difference in nuclear accumulation between islet cells from
neonatal and adult rats or between islets in vivo and isolated islets in
vitro. The results of these studies indicate that 1,25-[3H]dihydroxyvitamin
D3 target cells are present in islets before pancreatic beta-cells are
morphologically or functionally mature; islet beta-cells concentrate
1,25-dihydroxyvitamin D3, but not 25-hydroxyvitamin D3 or
24,25-dihydroxyvitamin D3. We conclude that only the 1,25-dihydroxyvitamin
D3 metabolite of vitamin D is accumulated by nuclei of developing and
mature beta-cells and suggest that 1,25-dihydroxyvitamin D3 plays a role in
the maturation of islet beta-cells.
