ANGIOTENSINOGEN GENOTYPE AND PLASMA-VOLUME IN NULLIGRAVID WOMEN

Objective: To determine if nonpregnant plasma volume is altered in wom en who are homozygous for the T 235 coding angiotensinogen allele, whi ch predisposes women to an increased risk of preeclampsia. Methods: We measured plasma volume by Evans blue dilution and analyzed it as a fu nction of angiotensinogen genotype in 15 nulligravid women during midf ollicular phase of 26 menstrual cycles. Eleven women were evaluated du ring two cycles, and four women were evaluated in one cycle. Fourteen women were white, and one was Asian. No subjects had illnesses or were taking medication. The range of body mass index (BMI [kg/m(2)]) was 2 0.2-31.0. Plasma volume (mL) was reported as plasma volume divided by BMI to control for variations in body sizes. Statistical analysis was performed by analysis of variance with post hoc testing using Fisher l east significant difference test for multiple comparisons (P < .05 acc epted for significance). Results: Angiotensinogen genotype analysis sh owed five women homozygous for M 235, three women homozygous for T 235 , and seven women who were heterozygous (MT 235). T 235 homozygotes ha d significantly lower plasma volume divided by BMI compared with women who were homozygous for M 235 and women who were heterozygous for MT 235 (mean + standard deviation [SD] [71.2 +/- 8.8, 86.6 + 5.2, 95.8 15.6, respectively, P < .05]). There was a tendency toward higher plas ma volume in heterozygote MT 235 compared with homozygote M 235 carrie rs, but it was not statistically significant. Conclusion: We conclude that the homozygous T 235 coding angiotensinogen genotype is associate d with reduced plasma volume in nulligravid women during the follicula r phase of the menstrual cycle compared with M 235 homozygotes and het erozygotes. This association of the T 235 coding genotype might contri bute to fetal growth restriction in preeclampsia. (Obstet Gynecol 1998 ;92:171-3. (C) 1998 by The American College of Obstetricians and Gynec ologists.)