The splenic factor influencing hepatic regeneration was investigated by using primary cultures of adult rat hepatocytes. The uptake of 3H-thymidine into DNA (DNA synthesis) of primary cultured hepatocytes reached maximum at 48 hours after initiation of incubation both in a splenic-extract added group and in a control-solution added group and the former showed significantly lower level (p less than 0.005) of uptake than did the latter. And the 3H-thymidine uptake was lower in a splenic venous serum added group than in an aortic or an inferior vena cava serum added group. This splenic DNA synthesis inhibiting activity was labile against heat and lost activity by trypsinization. Furthermore, when the splenic extract was subjected to gel filtration on a Sephadex G-75 column, DNA synthesis-inhibiting activity was observed in a certain fraction alone, and its molecular weight was estimated to be 50,000-60,000 daltons. Although extracts from thymus, lymph node and kidney also inhibited the uptake of 3H-thymidine, these DNA synthesis-inhibiting activities showed lower levels than that was shown in the splenic-extract added group. From these results, it is likely that a protein-like substance inhibiting hepatic regeneration is present in the spleen.
Animals Cells, Cultured