MITOTIC-ACTIVITY AND DNA-SYNTHESIS OF RAT ISLET CELLS FOLLOWING PARTIAL PANCREATECTOMY

The regenerative potential of the adult rat pancreas following a 50% pancreatectomy was investigated. Blood glucose values and body weight were unchanged by the procedure. The mitotic index (MI) of alpha, beta, and exocrine cells was examined in formalin-fixed sections of the pancreas stained for hormones and 5-bromo-2'-deoxyuridine (BrDU) after treating the animals with 2.5 mg/kg colchicine and/or 50 mg/kg BrDU prior to sacrifice. The MI was unchanged within the control group. For pancreatectomized versus control animals, in beta cells after 5 days the MI was 0.84% versus 0.41% (p < 0.05), while 7 days postoperatively it was 1.04% versus 0.57% (p < 0.01); in alpha cells, the MI was 0.32% versus 0. 17% (p < 0.05) at 5 days and 0.47% versus 0.24% (p < 0.05) at 7 days. The MI of exocrine cells rose transiently on day 3 postoperatively to 0.74% in the pancreatectomized group but remained low at 0.15% (p < 0.01) in the control group. The mean ratio of BrDU + ve beta cells was 1.19% in the pancreatectomy group and 0.45% in the control group on day 5 postoperatively (p = 0.01). A highly significant (r = 0.97; p < 0.001) correlation existed between BrDU + ve and mitotic cells. There was no difference between the two groups in the area occupied by insulin-positive cells in pancreatic sections, nor in the number of beta cells per islet. In conclusion, we describe a method for assessing cell growth in the pancreas following tissue depletion; endocrine celts in the adult rat pancreas are capable of transient regeneration after a partial pancreatectomy, temporally discordant from exocrine cells.