Age-related irreversible decrease in glutamine synthetase following liver cell proliferation.

The apparently permanent decrease in glutamine synthetase activity following partial hepatectomy in young adult rats has been studied further to include weanling and aged rats and other procedures that induced liver cell proliferation. In contrast to young adult rats, partial hepatectomy in weanling and aged rats did not produce a lasting decrease in liver glutamine synthetase activity. In addition to the surgical procedure, dietary regimentation and CCl4 poisoning also resulted in a lasting decrease in the liver enzyme in young adult rats. The enzyme activity present exclusively in the parenchymal cells of the liver declined progressively following each successive surgical operation. A combination of these procedures may be applicable to the production of a liver parenchymal cell line essentially devoid of the enzyme activity.