THYROID-HORMONE REGULATION OF PHOSPHOLIPASE A(1) AND A(2) ACTIVITY DURING ONTOGENY IN RATS - INVESTIGATION OF LIVER-CELLS AND THEIR NUCLEI

The process of phospholipid deacylation was studied in liver homogenat es, hepatocytes, and liver cell nuclei isolated from rats differing in age or thyroid status. Both the degradation of nuclear phospholipids (catalyzed by type A phospholipases) and their resynthesis in the pres ence of [H-3]arachidonate were shown to be controlled by thyroid hormo nes. Nuclear phospholipases A(1) and A(2) were found to play an import ant role in age-related dynamics of lipid composition of the nuclei, a s well as in the development of hypo- and hyperthyroidism. It was also demonstrated that thyroxin is capable of inhibiting in vitro and in v ivo liver cell phospholipase A(2) activity and prostaglandin E(2) prod uction; the content of this prostaglandin was decreased accordingly.