Does endogenous cyclic GMP inhibit potassium stimulated 45Ca uptake by P 2 fraction from rat brain?

Abstract

The effects of sodium azide (NaN 3), hydroxylamine (NH 2OH) and sodium nitroprusside on potassium-stimulated 45Ca uptake (K-stimulated 45Ca uptake) by P 2 fraction of Gray and Whittaker from rat brain were investigated. During preincubation with these reagents, the contents of cyclic GMP in synaptosomes increased, reaching maximum levels within 2 min. On preincubation for 2 min, NaN 3, an activator of membrane bound guanylate cyclase, inhibited K-stimulated 45Ca uptake, but NH 2OH and sodium nitroprusside did not affect it. Sodium cyanide, another metabolic inhibitor, had no effect on K-stimulated 45Ca uptake. There was a correlation between inhibition of K-stimulated 45Ca uptake and increase in the cGMP level on preincubation with NaN 3 for various periods. Based on these results role of cGMP in or around the membrane was discussed in relation to the K-stimulated 45Ca uptake by P 2 fraction.