Sexual Dimorphism of Sodium-Sensitive Renal-Wrap Hypertension

One-kidney, figure-8 renal wrap or sham operation was performed on male and female rats to determine if a difference existed in the expression of hypertension between the sexes. Animals were prepared with radiotelemetry transmitters to monitor mean arterial pressure and heart rate continuously throughout an 8-week study. Dietary sodium content was changed during the post-renal-wrap period from normal (100 micromol/g chow) to high (2000 micromol/g chow) to low (<2 micromol/g chow) to assess sodium sensitivity. Both male and female rats experienced an increase in arterial pressure after the renal-wrap procedure; however, the hypertension was significantly attenuated in the females. High salt caused a further increase in both groups of rats that was again attenuated in the female rats. Low sodium diet reduced arterial pressure in all groups of rats. Heart rate was significantly elevated in the female rats during all dietary interventions. The data were fit to a cosine function to analyze circadian rhythm changes. An increase in the light/dark difference for arterial pressure in the hypertensive rats during high salt diet resulted in an increase in the circadian amplitude (range of the rhythm). In the normotensive rats fed a high salt diet, the arterial pressure acrophase (peak of rhythm) was delayed while the heart rate acrophase was shifted to an earlier time. These studies showed that female rats are protected against one-kidney, figure-8 renal-wrap hypertension and are less sensitive to the effects of sodium.