The effects of exogenenous monoaminergic neurotransmitters (norepinephrine, NE; epinephrine, E; dopamine, DA and 5-HT) and
inhibin α N-terminal fragments P32 (1-32), p32-Tyr on P4 production by incubated
rat CL cells were studied. The results demonstrated that: (1) α fragments caused significant inhibition on P4 production. (2) 0. 1 mmol/L NE (or E) and 10 μmol/L DA produced a marked increase in both hasal and hCG induced P4 production by CL cells (P<0. 001). The rank orders of potency of the catecholamines in stimulating P4 production were different, for hasal P4 production, NE>E>DA; but for hCG induced P4 production, DA>E>NE, i. e. the order just reversed. Addition of P32-Tyr significantly neutrolized the stimulatory action of E, but only slightly increaed the action of NE. (3) α receptor blocker phentolamine and α receptor blocker propranolol were effective in decreasing hasal and hCG-induced P4 production,the latter being more effective than the former. It was further shown that both blockers augmented the inhibitory effect of α-fragments on P4 production. (4) UnlikeNE, E, and DA, 5-HT at 0. 5 μmol/L exerted inhibitory effect on the hasal and hCG-induced P4 production, but profoundly supressed the inhibitory effect of α-fragmentson P4 production. The above results suggested: (1) Adrenergic, DA and 5-HT receptors are present in rat CL, where
catecholamine might exert a stimulating effect on hasal and hCG-inducedP4 production via different pathways. (2) The inhibitory effect of P32, p32-Tyr on P4 production might be related to their inhibition by partial blocking α/β receptors, which were antagnized by 5-HT. (3) The action of P32, P32-TYr on P4 production is brought on the participation of neurotransmitters NE, E, DA and 5-HT.