Prejunctional facilitatory effect of a thiol-alkylating agent N -Ethylmaleimide on neurogenic contractions in rat prostate smooth muscle

Abstract

The effect of a non-specific thiol-alkylating agent N-ethylmaleimide (NEM) was studied on neurogenic contractile mechanisms in rat ventral prostate gland. Male Wistar albino rats were used. The rats were killed by cervical dislocation under sevoflurane anesthesia and ventral prostate gland was removed. Two preparations were obtained from each lobe. Neurally evoked isometric contractions were induced using trains of electrical field stimulation (EFS; 0.5, 1, 4, or 8 Hz). The effect of NEM on the contractions to EFS was examined in the absence or presence of adrenergic and/or purinergic antagonists. NEM enhanced the EFS-evoked contractions without altering the basal tone. These effects were significantly suppressed by an α(1) -adrenergic receptor antagonist (prazosin), a P2-purinergic antagonist (suramin), a specific P2X-receptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS), an ATP analog (α,β-methylene ATP), or a calcium channel blocker (verapamil). This facilitating effect of NEM did not occur following the administration of L-cysteine or glutathione which saturated NEM with excess thiols. However, a thiol-oxidant diamide failed to affect the contractions to EFS. An adrenergic neuron blocker (guanethidine) completely suppressed the responses to NEM. On the other hand, an α(2) -adrenergic receptor blocker (yohimbine), a nitric oxide synthase inhibitor (N(ω) -nitro-L-arginine) or a cholinergic muscarinic receptor antagonist (atropine) did not significantly affect the facilitatory response of NEM. These findings suggest that NEM has a prejunctional facilitatory action on the adrenergic nerves in rat prostate tissue to enhance release of transmitters, noradrenaline, and ATP. NEM sensitive proteins involved in transmitter release mechanisms can play a role in this effect.