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  • Title: Renal blood flow and its response to angiotensin II. An interaction between oral contraceptive agents, sodium intake, and the renin-angiotensin system in healthy young women.
    Author: Hollenberg NK, Williams GH, Burger B, Chenitz W, Hoosmand I, Adams DF.
    Journal: Circ Res; 1976 Jan; 38(1):35-40. PubMed ID: 1244226.
    Abstract:
    A variety of estrogen- and progestin-containing oral contraceptive agents reduced renal blood flow (RBF) significantly in 23 healthy, nonhypertensive young women, to a mean of 75 +/- 3.3% of the value expected for their age and dietary sodium intake (P less than 0.001). There was also significant activation of the renin-angiotensin system: renin substrate was increased approximately 3-fold in association with a striking increase in the circulating renin activity and angiotensin II levels in relation to sodium intake and excretion. Two observations suggest that the RBF reduction was directly mediated by angiotensin II. A correlation was demonstrable between circulating angiotensin II and RBF (P less than 0.01), and renal vascular responsiveness to angiotensin II infused into the renal artery was reduced significantly (P less than 0.001). Moreover, the oral contraceptive agents modified the basic relationship between sodium balance and vascular responsiveness to angiotensin II, suggesting that the agents acted through some mechanism other than alteration in the state of sodium balance. These observations provide further evidence for an important role of angiotensin II as a determinant of RBF. Renal vasoconstriction may contribute to the genesis of a number of complications, such as sodium retention and hypertension, associated with oral contraceptive use. The effects of oral contraceptive (OC) agents on sodium intake and the renin-angiotensin system were studied in 23 healthy young women. Renal blood flow (RBF) was significantly (p less than .001) reduced to 72-7 8% of the normal value for women of their age and level of sodium intake. In relation to sodium intake and excretion, renin substrate values were about 3 times higher than normal, and were associated with a considerable increase in circulating renin activity and angiotensin 2 levels. Levels of RBF and angiotensin 2 were significantly correlated (p less than .001) and renal vascular responsiveness to the infusion of angiotensin 2 into the renal artery was significantly reduced (p less than .001). This suggests that the reduction in RBF is directly mediated by angiotensin 2. The basic relationship between sodium balance and vascular responsiveness to angiotension 2 was also altered, which suggests that OCs work through mechanisms other than the modification of the sodium balance. Thus OCs, by virtue of renal vasoconstriction, may bring about various renal complications, such as sodium retention and hypertension.
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