In vivo arginine production and nitric oxide synthesis in pregnant Indian women with normal and low body mass indices.
OBJECTIVE
Nitric oxide (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 be a contributor to pregnancy-induced hypertension or preeclampsia. Because maternal weight is associated with blood pressure and risk of preeclampsia during pregnancy, it may also influence arginine and/or NO production. The purpose of this study was to determine the in vivo arginine production and NO synthesis rate in pregnant women with normal (n=10) and low (n=10) body mass indices (BMIs).


METHODS
Arginine flux and NO synthesis rate were measured in the postabsorptive state with constant infusions of 15N2-arginine and 13C,2H4-citrulline. Plasma concentrations of arginine and NO metabolites were also measured. Kinetic parameters were correlated to maternal variables, gestational age, birth weight and blood pressure.


RESULTS
Endogenous arginine flux was significantly faster in the low-BMI compared with normal-BMI women in the first trimester (63.1+/-3.4 vs 50.2+/-2.0 micromol/kg per h, P<0.01), but not in the second. Plasma NO concentration was higher (44.7+/-5.3 vs 30.4+/-1.9 micromol/l, P=0.03) and its rate of synthesis trended faster in the low-BMI compared with normal-BMI group in the second trimester. Maternal weight and BMI were negatively correlated with arginine flux in both trimesters and NO synthesis in the second trimester.


CONCLUSIONS
These findings suggest, but do not prove, that maternal BMI may be a factor in the ability to produce NO during pregnancy and may be one way by which BMI influences blood pressure during pregnancy.
St John's Research Institute, St John's National Academy of Health Sciences, Bangalore, India.
A V
AV
Kurpad
C
C
Kao
P
P
Dwarkanath
S
S
Muthayya
A
A
Mhaskar
A
A
Thomas
M
M
Vaz
F
F
Jahoor
D000293:Adolescent; D000328:Adult; D001120:Arginine / Q000097:blood*; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D005260:Female; D006801:Humans; D007194:India; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000097:blood; D050177:Overweight / Q000097:blood / Q000150:complications*; D011247:Pregnancy / Q000097:blood / Q000378:metabolism*; D011248:Pregnancy Complications / Q000097:blood*; D011261:Pregnancy Trimester, First / Q000097:blood; D011262:Pregnancy Trimester, Second / Q000097:blood; D012016:Reference Values; D055815:Young Adult
D009569:Nitric Oxide; D001120:Arginine