The Effects of Superoxide Anion Generators on Responses to Exogenous Nitric Oxide and Non‐Adrenergic, Non‐Cholinergic Nerve Stimulation in Rat Isolated Penile Bulb

Abstract

The effects of the superoxide anion generators, pyrogallol and hydroquinone on relaxations induced by electrical field stimulation (70 V, 0.7 msec., 0.5-8 Hz for 5 sec.) and exogenous nitric oxide donor sodium nitroprusside, were investigated in rat penile bulb precontracted with phenylephrine (10 ª4 M). Pyrogallol (10 ª4 M, 3¿10 ª4 M) and hydroquinone (3¿10 ª4 M) reduced the relaxations induced by sodium nitroprusside, but had no effect on relaxations elicited by nitrergic nerve stimulation. After treatment with diethyldithiocarbamate (3¿10 ª3 M), an inhibitor of Cu/Zn superoxide dismutase, both agents reduced the relaxations induced by electrical field stimulation. Superoxide dismutase, at 300 U/ml, significantly reversed the inhibitory action of pyrogallol and hydroquinone on responses to sodium nitroprusside. This concentration of superoxide dismutase failed to reverse the inhibitory action of pyrogallol on responses to electrical field stimulation observed in the presence of diethyldithiocarbamate, while at 600 U/ml it significantly prevented the reduction in relaxations. However, even at 600 U/ml, superoxide dismutase did not alter the decrease in responses to electrical field stimulation evoked by hydroquinone in tissues pretreated with diethyldithiocarbamate. These results suggest that the nitrergic transmitter in rat penile bulb is protected against superoxide anions by endogenous Cu/Zn superoxide dismutase in a manner similar to gastric fundus and anococcygeus muscles.

Torsion/Detorsion of the Testis Does Not Modify Responses to Nitric Oxide in Rat Isolated Penile Bulb

“…Nitric oxide has been found to be co‐localized with Cu/Zn superoxide dismutase in neuroeffector junctions and is protected from destruction by superoxide anions via this enzyme in mouse anococcygeus [15], bovine retractor penis [16] and rat anococcygeus [17] muscles. Our recent finding that relaxations to electrical field stimulation were reduced by superoxide anion generators after inhibition of endogenous Cu/Zn superoxide dismutase with DETCA presents strong evidence about the existence of the above mentioned protection in rat penile bulb [9]. However, in the present study, the relaxant responses to electrical field stimulation were found unchanged after 2 or 24 hr of detorsion following torsion.…”

“…Ischaemia reperfusion injury has been associated with the overgeneration of reactive oxygen and nitrogen species [8]. In our previous study, we found that oxygen‐free radicals reduced nitrergic nerve‐mediated relaxant responses only in the presence of an inhibitor of endogenous Cu/Zn superoxide dismutase in rat penile bulb [9]. Besides, we have recently demonstrated that unilateral testicular torsion in the rat reduces neurotransmitter release from nerve terminals in the ipsilateral vas deferens [7].…”