NO has been proposed as a mediator of vascular expansion during pregnancy. Inability to increase NO synthesis and/or production of its precursor,
arginine, may contribute to
pregnancy-induced hypertension. Adolescents have a higher incidence of
gestational hypertension. It is not known whether pregnant adolescents can produce sufficient
arginine to meet overall demands. Our objective was to measure and compare the
arginine flux and NO synthesis rates of pregnant adolescents and adult women.
Arginine,
citrulline, and NO kinetics were measured by i.v. infusions of (15)N(2)-argininine and (2)H(2)-citrulline in 8 adolescents and 8 adult women in the fasted state at the end of the first and the beginning of the 3rd trimesters of pregnancy.
Arginine flux decreased (P < 0.05) from trimester 1 to 3 in the adolescents but not in the adult women. NO synthesis rate did not change significantly in either group from trimester 1 to 3. In trimester 3, there was a positive association (r = 0.55; P = 0.02) between
arginine flux and participants' age, indicating that flux was slower in the younger participants. These findings suggest that after a brief period of food deprivation, the pregnant adolescent cannot maintain
arginine production like her adult counterpart in late pregnancy. This inability to maintain
arginine production seems to be related to her younger age. It does not, however, affect her ability to synthesize NO in late pregnancy.