Effect of oral contraceptives on the renin angiotensin system and renal function

We examined the effect of oral contraceptive (OC) usage on the renin angiot ensin system (RAS) in two related experiments. In the first experiment, sub jects were 34 healthy, normotensive, premenopausal women, 15 OC users and 1 9 OC nonusers, mean age 25 +/- 1 yr, ingesting a controlled sodium diet. We assessed arterial pressure, glomerular filtration rate, effective renal pl asma flow, renal vascular resistance (RVR), and filtration fraction (FF) us ing inulin and p-aminohippurate clearance techniques, both at baseline and in response to the ANG II receptor blocker losartan. In the second experime nt, in similar subjects, 10 OC users and 10 nonusers, we examined circulati ng RAS components [angiotensinogen, ANG II, aldosterone, plasma renin activ ity (PRA), and active renin] in response to incremental lower body negative pressure (LBNP), to determine whether renin secretion is suppressed by OC usage. OC users exhibited elevations in systolic blood pressure, RVR, and F F compared with nonusers, which were partially corrected by losartan. In th e LBNP phase of the study, baseline measures of PRA, angiotensinogen, ANG I I, and aldosterone were all increased in the OC group compared with the con trol group. Active renin levels did not differ between groups. Incremental LBNP resulted in increased circulating levels of RAS components in both gro ups. We conclude that the RAS is activated in women using OCs. There was no evidence that decreases in renin secretion result in normalization of the RAS as a whole.