Regulation of islet beta-cell proliferation by prolactin in rat islets.
This study examined the effects of prolactin on beta-cell proliferation in pancreatic islet of Langerhans. Insulin secretion and beta-cell proliferation were significantly increased from neonatal rat islets cultured for 4 days in the presence of either 500 ng/ml ovine prolactin (oPRL) or rat prolactin (rPRL). These effects could be prevented by including anti-oPRL serum in the culture media. Although insulin secretion and beta-cell proliferation were slightly higher during the first 24 h of exposure to rPRL, maximal response was observed after 4 days for insulin secretion and 6-10 days for beta-cell proliferation. The initial mitogenic response of beta-cell to rPRL occurred by the limited recruitment of nondividing beta-cells into the cell cycle and by most daughter cells proceeding directly into additional cell division cycles. Subsequently, the maximal effect of rPRL on beta-cell proliferation was maintained by a higher rate of recruitment of previously nondividing beta-cells into cell cycle with only one fourth of the daughter cells continuing to divide. These observations are difficult to reconcile with the proposal that a limited pool of beta-cells capable of undergoing cell division exists in islets. Instead, these observations suggest that individual beta-cells are transiently re-entering the cell cycle and dividing infrequently in response to rPRL. In this case, the majority of the beta-cells would not be expected to be in an irreversible Go phase. We also demonstrated that the effects of rPRL on beta-cell proliferation occur at normal serum glucose concentrations and are affected by inhibitors of polyamine metabolism. Additional studies on the effects of rPRL on beta-cells should provide important information on the regulation of beta-cell proliferation during conditions of increased insulin demand.
Brelje
T C
TC
University of Minnesota Medical School, Department of Cell Biology and Neuroanatomy, Minneapolis 55455.
Parsons
J A
JA
Sorenson
R L
RL
D000480:Alkynes; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D003078:Colchicine / Q000494:pharmacology; D003959:Diamines / Q000494:pharmacology; D000518:Eflornithine / Q000494:pharmacology; D006918:Hydroxyurea / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007700:Kinetics; D065108:Ornithine Decarboxylase Inhibitors; D017239:Paclitaxel / Q000494:pharmacology; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D000480:Alkynes; D003959:Diamines; D007328:Insulin; D065108:Ornithine Decarboxylase Inhibitors; C039613:6-heptyne-2,5-diamine; D011388:Prolactin; D017239:Paclitaxel; D003078:Colchicine; D006918:Hydroxyurea; D000518:Eflornithine