1. Platelet angiotensin II binding was measured in 34 primigravid women (between 28 and 32 weeks gestation), in whom the pressor response to infused angiotensin II was also determined.
2. There was a significant correlation between the platelet angiotensin II binding and the slope of the curve relating the diastolic pressor response to infused angiotensin II (P<0.01), suggesting that co-linearity between the two techniques exists and supporting the use of platelet angiotensin II binding as a model of vascular smooth muscle pressor responsiveness.
3. Ten of the 34 women subsequently developed pregnancy-induced hypertension. Platelet angiotensin II binding in the patients who subsequently developed pregnancy-induced hypertension was sixfold higher than in the patients who remained normotensive (P < 0.001). There were, however, no significant differences between the groups in any of the parameters derived from the angiotensin II infusion experiments.
4. The use of platelet angiotensin II binding alone in predicting the outcome of the pregnancies, as assessed using discriminant analysis, was more successful than when any of the infusion parameters were used, with 77% of patients being correctly classified.