AGING REDUCES THE NUMBERS OF HEPATOCYTES SYNTHESIZING DNA IN RESPONSETO EGF AND EPINEPHRINE

Primary cultures of hepatocytes were prepared from young (6 month) and old (24 month) Wistar rats and exposed to epinephrine or epidermal gr owth factor. Incorporation of [H-3]thymidine into DNA was determined b oth radiochemically and autoradiographically, The numbers of respondin g cells and degree of response per cell were determined and the result s confirmed by FACScan analysis. Such analyses clearly demonstrate a r educed number of hepatocytes capable of responding to the above stimul i in cultures obtained from old rats, Thus, changes in numbers of resp onding cells may be an important mechanism involved in reduced respons iveness of the aged liver to agents which stimulate DNA synthesis and cell division. (C) 1997 Academic Press.