Increased particulate and decreased soluble guanylate cyclase activity in regenerating liver, fetal liver, and hepatoma.

We determined the activities of soluble and particulate guanylate cyclase [GTP pyrophosphatelyase (cyclizing); ?EC 4.6.1.2] IN REGENERATING RAT LIVER, FETAL AND NEONATAL RAT LIVER, AND HEPATOMA. TIn these tissues we found increased particulate and decreased soluble enzyme activities compared to normal adult rat liver. The particulate activity increased 12 hr after partial hepatectomy, reached maximal activity at 48 hr, and then declined. The soluble enzyme activity decreased within 8 hr and continued to decline. The activity of homogenates did not change. Guanylate cyclase activity was increased in plasma membrane and microsome fractions from regenerating liver. The increase in particulate activity was prevented with cycloheximide. Decreased soluble and increased particulate enzyme activities were found in fetal liver. After birth the soluble activity increased and the particulate activity decreased. Seven to 14 days after birth the activities of soluble and particulate fractions were similar to those of adult rat liver. In hepatoma 3924A, the activity of particulate guanylate cyclase was 9-fold greater and that of the soluble enzyme was 50% that of normal liver. These studies suggest that guanylate cyclase activity and its subcellular distribution may be related to liver growth through some unknown mechanism.