Abstract
The effect of lithium (Li) on the stimulation of adenylate cyclase by prostaglandin E 1(PGE 1) was examined. In platelet sonicates, Li, as well as sodium (Na), potassium (K), and rubidium (Rb) significantly reduced the PGE 1-induced stimulation of adenylate cyclase in a dose-dependent manner. The inhibition due to Rb was significantly less than that produced by the other cations; at a high concentration, 64 mM, Li was a more potent inhibitor than the other cations. In intact platelets, only Li reduced the PGE 1-enhanced accumulation of [ 3H]cyclic AMP, K and Rb being ineffective. As little as 1 mM Li significantly reduced the stimulatory effect of PGE 1 on [ 3H]cyclic AMP production in this sytem. The inhibition produced by Li was not blocked by phentolamine, whereas phentolamine did block the inhibition due to norepinephrine (NE). Magnesium enhanced the stimulatory effect of PGE 1 on the production of labeled cyclic AMP in intact platelets and antagonized the inhibition produced by Li on this process. These data show that Li antagonizes PGE 1 − induced stimulation of platelet adenylate cyclase at a site distinct from that at which NE acts.
Published Version
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