DIGOXIN-LIKE IMMUNOREACTIVE SUBSTANCE AND SODIUM-POTASSIUM-ADENOSINE TRIPHOSPHATASE INHIBITION IN NORMAL-PREGNANCY - A LONGITUDINAL-STUDY

Objective: To measure the levels of digoxin-like immunoreactive substa nce and digitalis-like factor bioactivity as manifested by sodium-pota ssium-adenosine triphosphatase (ATPase) inhibition throughout pregnanc y. Methods: Serum samples were collected from primigravidas in early ( 15 +/- 1.8 weeks), mid (26 +/- 1.2 weeks), and late (36 +/- 1.1 weeks) gestation, as well as at 6 +/- 1.1 weeks postpartum (mean +/- standar d error). Digoxin-like immunoreactive substance levels were determined by radioimmunoassay and digitalis-like factor bioactivity was determi ned by inhibition of ATPase. Data were analyzed by means of repeated m easures analysis of variance. Results: In 41 women with normal pregnan cy outcomes, levels of digoxin-like immunoreactive substance rose prog ressively and significantly (P < .001) throughout pregnancy and return ed to normal levels postpartum. Inhibition of ATPase activity also ros e significantly (P < .004), but not as dramatically, during pregnancy and remained elevated 6 weeks postpartum Conclusion: Although digoxin- like immunoreactive substance levels rise in pregnancy, functional dig italis-like factor activity, as manifested by inhibition of ATPase, do es not parallel this rise strictly, implying that digoxin-like immunor eactive substance receptors may be reset during normal pregnancy. The enhanced cardiac performance that occurs in normal pregnancy may be me diated in part by increased digitalis-like factor activity. (C) 1997 b y The American College of Obstetricians and Gynecologists.