Angiotensinogen genotype and plasma volume in nulligravid women

Objective: To determine if nonpregnant plasma volume is altered in women who are homozygous for the T 235 coding angiotensinogen allele, which predisposes women to an increased risk of preeclampsia. Methods: We measured plasma volume by Evans blue dilution and analyzed it as a function of angiotensinogen genotype in 15 nulligravid women during midfollicular phase of 26 menstrual cycles. Eleven women were evaluated during 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 20.2-31.0. 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 least significant difference test for multiple comparisons (P < .05 accepted for significance). Results: Angiotensinogen genotype analysis showed five women homozygous for M 235, three women homozygous for T 235, and seven women who were heterozygous (MT 235). T 235 homozygotes had 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 plasma volume in heterozygote MT 235 compared with homozygote M 235 carriers, but it was not statistically significant. Conclusion: We conclude that the homozygous T 235 coding angiotensinogen genotype is associated with reduced plasma volume in nulligravid women during the follicular phase of the menstrual cycle compared with M 235 homozygotes and heterozygotes. This association of the T 235 coding genotype might contribute to fetal growth restriction in preeclampsia. (Obstet Gynecol 1998;92:171-3. (C) 1998 by The American College of Obstetricians and Gynecologists.)