[Increased red-cell sodium-lithium countertransport activity and urinary 11-dehydrothromboxane B2 during pregnancy]

The activity of Na-Li countertransport (CT), a marker of the risk of essential hypertension, was determined in 55 primigravid women during pregnancy, together with urinary 11-dehydro-thromboxane B2 (11-dehydro-TXB2) as a marker of thromboxane A2 synthesis. The mean Na-Li CT (mean +/- SEM) value was increased significantly at 20 weeks gestation and thereafter, and reached higher levels in late pregnancy than in non-pregnant controls (0.31 +/- 0.02 vs. 0.21 +/- 0.01mmol per hr per liter RBC, p less than 0.05). Fifty five primigravid women could be divided into two groups, depending upon Na-Li CT activity either higher or lower than the value of 0.25mmol per hr per liter RBC at any time in the pregnancy up to term. At 20 weeks gestation all but one of 13 women in the lower-activity group had Na-Li CT activity less than 0.20 mmol per hr per liter RBC, and none developed PIH, whereas out of 42 women in the higher-activity group, all but one had Na-Li CT activity more than this value, and 8 developed PIH. Urinary 11-dehydro-TXB2 increased as pregnancy progressed, maximum levels being attained in women at term, about 3 times higher than in controls (4.19 +/- 0.35 vs. 1.36 +/- 0.10 ng per mg creatinine, p less than 0.05). Although the formation of thromboxane A2 was reported to be higher in pregnancy complicated by hypertension, no significant difference existed in the levels of 11-dehydro-TXB2 between women with PIH and women with uncomplicated pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)