Gender difference in bioassayable endothelium-derived nitric oxide from isolated rat aortae.

Gender differences in the production/release of endothelium-derived nitric oxide (EDNO) was assessed by determining the ability of intact endothelium to suppress serotonin- (10(-7)-10(-5) M) and phenylephrine-induced (10(-9)-(10(-5) M) contractions in thoracic aortae isolated from male and female Wistar rats mounted in organ chambers for isometric tension recording or tested in bioassay experiments. The endothelium suppressed these contractions significantly more in aortae from female than from male rats. In the bioassay, the perfusate from intact female thoracic aortic segments produced a significantly greater relaxation of the detector rings than that from the aortae isolated from male rats. Acetylcholine (10(-9)-10(-5) M), used to investigate agonist-induced release of EDNO, evoked significantly greater endothelium-dependent relaxation in aortae from female rats. The unstimulated release of 6-ketoprostaglandin F1 alpha and thromboxane B2 from intact thoracic aortic rings from male and female rats was not significantly different. There was no difference in smooth muscle reactivity to sodium nitroprusside (10(-10)-10(-6) M) in rings without endothelium. These results indicate that EDNO production/release is higher in thoracic aortae isolated from female rats.