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.