Histochemical Studies of Enzymatic Behaviour in the Hepatic Cells of the Senile Rat Liver.

As a part of the investigation on the senile changes, histochemical findings of some enzyme activities in the resting and regenerating liver have been compared between senile and young adult rats. In the resting senile liver, succinate dehydr.ogenase, cytochrome oxidase and glucose-6-phosphataseexhibited a tendency to decrease in activity, especially in the central and mid-zonal areas of the lobule, but peripheral hepatic cells rather showed a high activity. Acid phosphatase activity was sligntly weak. TPN-linked glucose6-phosphate dehydrogenase activity was remarkably s:tronger throughout the lobule in the senile case, and DPN-linked la~tate dehydrogenase activity was .also higher especially in the periportal area. Alkaline phosphatase activity wa!l also more pronounced in tlie senil~ ca~e. in the liver reg~·n~ni.tfrig 'after partill'l ·hepatectonry, the early decrease in succinate ·dehydrogenase ·activity was m .ore .marked, and ·. the restoration of the activity was delayed in the senile case. The TP~-1inked glucose-6-phosphate dehydrogenase and the DPN-linked lactate dehydrogenase in the reg!'!nerating liver showed similar changing patterns between the young and senile cases, and their activities in the senile which were higher than those in the young in the resting stage were sur· passed by those in the young at the peak of mitotic activity. On the contrary, the changing pattern of glucose-6-phosphatase activity in the senile and that in the young adult differed from each other. The activity . de· creased in the young adult and increased in senile case eariy after hepatectomy, and it reached the minimum in the former and the maximum in the latter at the peak of mitotic activity. It is also noted that the giant-nuclear and binucleate hepatic cells which were observed more frequently in the senile liver showed usually a high level in succinate dehydrogenase, TPN-linked glucose-6-phosphate dehydrogenase, DPN-linked lactate dehydrogenase, DPN diaphorase, cytochrome oxidase and glucose-6-phos· phatase activities.