Measurement of pancreatic islet cell proliferation by heavy water labeling

We describe a sensitive technique for measuring long-term islet cell proliferation rates in vivo in rats. Pancreatic islets were isolated and the incorporation of deuterium ( 2 H) from heavy water ( 2 H 2 O) into the deoxyribose moiety of DNA was measured by GC-MS. The results of heavy water labeling and BrdU staining were compared. The two methods were highly correlated ( r = 0.9581, P < 0.001). Based on long-term heavy water labeling, ∼50% of islet cells divided in rats between 8 and 15 wk of age. Of interest, long-term BrdU administration suppressed proliferation of islet cells significantly, but not of bone marrow cells. Physiological evidence further supported the validity of the method: older animals (24 wk old) had 60% lower islet cell proliferation rates than younger rats (5 wk old), and partial (50%) pancreatectomy increased proliferation by 20%. In addition, cholecystokinin-8 treatment significantly stimulated proliferation in pancreatectomized rats only. In summary, heavy water labeling is a quantitative approach for measuring islet cell proliferation and testing therapeutic agents.