The possible role of digitalislike factors in pregnancy-induced hypertension.

A group of small, digitalislike compounds has been implicated in some forms of essential hypertension. Because of similarities between these forms of essential hypertension and pregnancy-induced hypertension, the presence of digitalislike factors in pregnancy-related fluids has been investigated. The factors are found in maternal sera with significantly higher levels of digitalislike activity, as monitored by digoxin radioimmunoassay, in the sera of third-trimester women with pregnancy-induced hypertension as compared to normotensive third-trimester controls (315 vs 195 pg digoxin equivalents/ml; p less than 0.001). Similarly, they are found in amniotic fluid, and significantly higher levels, as measured by radioimmunoassay (760 vs 540 pg digoxin equivalents/ml; p less than 0.0008) and by inhibition of ouabain-sensitive Na+,K+-adenosine triphosphatase (ATPase) (12.8 vs 2.7% inhibition; p less than 0.002), are found in those women whose pregnancies are complicated with hypertension. With purification, several digoxinlike immunoactive compounds are detected. Of these, some have a marked ability to inhibit ouabain-sensitive Na+,K+-ATPase. While as yet unidentified, these compounds have properties suggesting that they are not peptides, steroids, or fatty acids and lipids.