Hypothalamic prostaglandin E2 receptors coupled to an adenylyl cyclase

We show that the effect of prostaglandin (PG) E2 on luteinizing hormone-releasing hormone (LHRH) release involves a receptor-mediated process coupled to an adenylyl cyclase system. The adenylyl cyclase activity in rat hypothalamus synaptic membrane preparations was stimulated by PGE2 and this stimulation was directly related to the presence of guanine nucleotide (GTP). PGE2 specifically bound to P2 membranes from rat and porcine hypothalami with similar characteristics. Computer-fitted saturation curves provided evidence for two binding components which may be two states of the same receptor (RH and RL). Experiments with Gpp(NH)p, a non-metabolizable analogue of GTP, suggested the interconversion of RH and RL. These results may reflect different states of the ternary complex (hormone-receptor-guanine binding protein). Magnesium (Mg2+) can modify the RH and RL binding parameters, but seems to act directly on the PGE2 receptor site.