Normal pregnancy is associated with increased levels of digitalis-like factor (DLF) and erythrocyte sodium-lithium countertransport (RBC CTT), which return to normal levels postpartum. Patients with pregnancy-induced hypertension (PIH) have greater increases in both factors than women with normotensive pregnancies. This study was designed to determine if both abnormalities are observed concomitantly in PIH, if they correlate with blood pressure, if they correlate negatively with a hormonal index of volume status (PRA), and if they differ in women with and without proteinuria. Twenty-six normotensive women and 26 women with PIH were studied in the third trimester. Thirteen of these patients were also studied 6 months postpartum. Women with PIH, compared to those who were normotensive, had higher RBC CTT (0.49 +/- 0.04 vs. 0.36 +/- 0.03 mmol Li/L cells.h; P = 0.004) and DLF (0.30 +/- 0.3 vs. 0.20 +/- 0.03 microgram digoxin equiv./L; P = 0.01) and lower PRA [4.58 +/- 0.76 vs. 7.34 +/- 0.86 ng/mL.h (1.27 +/- 0.21 vs. 2.04 +/- 0.24 ng/L.s); P = 0.001]. All three parameters correlated significantly with diastolic blood pressures (RBC CTT and DLF positively (P less than or equal to 0.02) and PRA negatively (P = 0.03). Comparisons of DLF, RBC CTT, and PRA demonstrated a significant correlation of RBC CTT and DLF for normotensive pregnant women only (r = 0.38; P = 0.05). Patients with PIH were further analyzed according to whether proteinuria (24-h urinary protein, greater than 0.30 g; urine dipstick, greater than or equal to 2+) was present or absent. There was no significant difference in diastolic blood pressure or PRA between the hypertensive subpopulations, although there was a tendency for those without proteinuria to have lower PRAs [3.85 +/- 0.80 ng/mL.h (1.07 +/- 0.02 ng/L.s)] than those with proteinuria [5.31 +/- 1.30 ng/mL.h (1.48 +/- 0.36 ng/L.s)]. RBC CTT was significantly higher (P less than 0.05) in women with PIH without proteinuria, whereas serum DLF was significantly higher in women with PIH with proteinuria (P less than 0.05). In 13 women studied 6 months postpartum, there was a significant reduction in serum DLF, RBC CTT, and PRA for all women and in blood pressure for women who had had PIH (P less than 0.01). Thus, women with PIH, compared to normotensive pregnant women, had abnormalities in a variety of factors known to be volume sensitive or indicative of salt- and volume-sensitive forms of hypertension.(ABSTRACT TRUNCATED AT 400 WORDS)