Inhibition of nuclear T3 binding by fatty acids liberated from nuclear membranes via phospholipase C.

1. We have investigated whether phospholipase C (PLC) might act on phospholipids in the nuclear membrane of rat liver, resulting in inhibition of nuclear T3 binding (INB activity). 2. Incubation of intact nuclei with PLC caused a time- and dose-dependent increase of INB activity; this was correlated with a rise of the free fatty acid concentration in the nuclear ether extract. 3. Removal of the nuclear membrane resulted in a loss of INB activity of the nuclei. 4. Other compounds liberated by the action of PLC (such as diacylglycerols, IP3 and phosphoalcohols), had no INB activity. 5. We conclude that PLC can liberate fatty acids from the rat liver-nuclear membrane via further degradation of the direct product diacylglycerol. 6. These fatty acids display inhibition of nuclear T3 binding in vitro.