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

Enlargement of the uterine artery (UA) during pregnancy is diminished in wo men residing at a high altitude. We asked whether chronic hypoxia alters th e rise in DNA synthesis in uteroplacental vessels and, if so, whether the r eduction is related to the intrauterine growth retardation (IUGR) observed under conditions of chronic hypoxia. We used bromodeoxyuridine (BrdU) label ling to measure DNA synthesis in all vascular layers of the UA, mesometrial arteries (MA), thoracic aorta and mesenteric artery of guinea pigs, residi ng throughout pregnancy at a low (1600 m) or high (3962 m) altitude. Pregna ncy increased DNA synthesis throughout the UA at both altitudes, yet the ma ximal value was less at high than low altitude (P<0.05). Likewise, pregnanc y 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 growth response by the uteroplacental vasculatu re to pregnancy may contribute to the previously reported reduced uterine a rtery blood flow and resulting IUGR at high altitude. (C) 2000 Harcourt Pub lishers Ltd.