Chronic hypoxia diminishes pregnancy-associated DNA synthesis in guinea pig uteroplacental arteries.

Enlargement of the uterine artery (UA) during pregnancy is diminished in women residing at a high altitude. We asked whether chronic hypoxia alters the rise in DNA synthesis in uteroplacental vessels and, if so, whether the reduction is related to the intrauterine growth retardation (IUGR) observed under conditions of chronic hypoxia. We used bromodeoxyuridine (BrdU) labelling to measure DNA synthesis in all vascular layers of the UA, mesometrial arteries (MA), thoracic aorta and mesenteric artery of guinea pigs, residing throughout pregnancy at a low (1600 m) or high (3962 m) altitude. Pregnancy increased DNA synthesis throughout the UA at both altitudes, yet the maximal value was less at high than low altitude (P<0.05). Likewise, pregnancy increased DNA synthesis throughout the MA, yet at high altitude pregnancy elevated levels returned to non-pregnant values after 42 days of gestation, whereas at low altitude DNA synthesis continued to be elevated until near term. Fetal weights were lower (P=0.01) and placental/fetal weight ratios tended to be greater in high than low altitude, near term pups (P = 0.09). We conclude that a diminished growt response by the uteroplacental vasculature to pregnancy may contribute to the previously reported reduced uterine artery blood flow and resulting IUGR at high altitude. Copyright 2000 Harcourt Publishers Ltd.