Platelet angiotensin II binding sites in normotensive and hypertensive women.

Specific binding of angiotensin II (AII) to platelets was measured in 89 women, 25 nulliparous non-pregnant women and 64 primigravida in the third trimester of pregnancy. There was significantly lower binding in the 25 pregnant women who were normotensive (2.3 fmol/10(9) cells) when compared with the non-pregnant women (9.0 fmol/10(9) cells P less than 0.001). Significantly higher platelet AII binding levels were found in the 39 women who had pregnancy induced hypertension (PIH) (5.5 fmol/10(9) cells) when compared with the 25 normotensive pregnant women (P less than 0.001). Of the 39 women with PIH, platelet AII binding was higher in the 23 women who had pre-eclampsia (7.0 fmol/10(9) cells), when compared with the 16 who had non-proteinuric PIH, (4.6 fmol/10(9) cells) although the difference was not statistically significant (P less than 0.04). The pressor response to AII is also diminished in pregnancy, yet less so if pregnancy induced hypertension develops. Platelets may provide a readily accessible tissue with which to study AII responsiveness in pregnancy.