TRANSPLANTED BETA-CELL RESPONSE TO INCREASED METABOLIC DEMAND - CHANGES IN BETA-CELL REPLICATION AND MASS

We determined the capacity of transplanted beta cells to modify their replication and mass when stimulated by changes in metabolic demand. F ive groups of Lewis rats were studied: group 1 (Tx-Px) had a 95% pancr eatectomy 14 d after transplantation of 500 islets; group 2 (Px-Tx) ha d a 95% pancreatectomy 14 d before transplantation of 500 islets; grou p 3 (Tx) was transplanted with 500 islets; group 4 (Px) had a 95% panc reatectomy; and group 5 (normal) was neither transplanted nor pancreat ectomized. Blood glucose was normal in Tx-Px and Tx groups at all time s. Px-Tx and Pr groups developed severe hyperglycemia after pancreatec tomy that was corrected in Px-Tx group in 83% of rats 28 d after trans plantation. Replication of transplanted beta cells increased in Tx-Px (1.15+/-0.12%) and Px-Tx (0.85+/-0.12%) groups, but not in Tx group (0 .64+/-0.07%) compared with normal pancreatic beta cells (0.38+/-0.05%) (P < 0.001). Mean beta cell size increased in Tx-Px (311+/-14 mu m(2) ) and Px-Tx (328+/-13 mu m(2)) groups compared with Tx (252+/-12 mu m( 2)) and normal (239+/-9 mu m(2)) groups (P ( 0.001). Transplanted beta cell mass increased in Tx-Px (1.87+/-0.51 mg) and Px-Tx (1.55+/-0.21 mg) groups compared with Tx group (0.78+/-0.17 mg) (P < 0.05). In summ ary, changes in transplanted beta cells prevented the development of h yperglycemia in Tx-Px rats. Transplanted beta cells responded to incre ased metabolic demand increasing their beta cell mass.