Gender differences in vascular reactivity of aortas from rats with and without portal hypertension

Inflammatory responses related to portal hypertension may be different in male and female rats. Most experimental studies of portal hypertension have involved male animals, and little information is available on gender differences in this setting. The aim of the present study was to compare aortic reactivity in female and male rats with and without portal hypertension.

Contraction response curves to phenylephrine were studied with aortic rings, with and without endothelium. For relaxation studies, rings were precontracted with phenylephrine 10(-7) mol/L and then exposed to acetylcholine 10(-4) mol/L. Portal hypertension was provoked by calibrated portal stenosis performed 2 weeks before experiments.

In non-hypertensive conditions, the contractile response to increasing phenylephrine concentrations was significantly stronger in rings from male than female rats, both with and without endothelium. In male rats with portal hypertension, the phenylephrine concentration-response curves were lowered and shifted to the right in aortic rings both with and without endothelium. In female rats, portal hypertension did not induce significant changes in the phenylephrine concentration-response curves. In female rats, portal hypertension induced a marked increase in relaxation (157 +/- 123% vs 81 +/- 64% in controls); the increase was also stronger than that in male rats with portal hypertension (95 +/- 6%; P < 0.01).

Clear gender differences were observed in vasoconstrictor responsiveness of aortic rings from rats with and without portal hypertension. Contrary that in male rats, portal hypertension did not induce vascular hyporesponsiveness in female rats. Further investigations are required to explain these differences.