Sex differences in pressure diuresis/natriuresis in rabbits

We tested for sex-related differences in the pressure diuresis/natriuresis relationships in anaesthetized, renally denervated rabbits, using an extrac orporeal circuit to perfuse the left kidney with the rabbit's own blood, th rough a series of step-wise increases in renal artery pressure (RAP) (from 65 to 130 mmHg). Urine flow, sodium excretion, and the fractional excretion s of sodium and urine increased with increasing RAP, and were greater in ma le than in female rabbits at all levels of RAP-tested. However, these appar ent sex-related differences in the acute pressure diuresis/natriuresis rela tionships were not reflected in alterations in chronic regulation of mean a rterial pressure (MAP). Thus, in rabbits on a normal salt diet (0.85 g day( -1)), resting conscious MAP was significantly greater in males (87 +/- 3 mm Hg) compared with females (77 +/- 1 mmHg). Chronically increasing dairy sal t intake to 4.98 g day(-1) for 28 days had no significant effect on resting conscious MAP in either sex. Thus, although our observations indicate sex differences, at least under the present experimental conditions, in the fac tors regulating extracellular fluid volume, these do not appear to have a m ajor impact in setting the level of MAP in the long term.