LACTATION AND PREGNANCY EFFECTS ON BLOOD-FLOW TO MAMMARY AND REPRODUCTIVE SYSTEMS IN HEAT-STRESSED RABBITS

This study used radioactive microspheres to examine blood flow distrib ution in the mammary and reproductive systems of hyperthermic (+1 degr ees C), anesthetized laboratory rabbits at different stages of pregnan cy and lactation. Ovarian, cervical and oviductal blood flows decrease d by 20-30% during heat stress while vulval blood flow rose by 40%, ir respective of pregnancy and/or lactation status. Mammary blood flow wa s unaltered during heat stress at most pregnancy and/or lactation stag es, with the exception of a 35% decrease in nonpregnant rabbits in ear ly lactation. Uterine blood flow in non-pregnant rabbits in early and peak lactation decreased by 42% and rose by 33%, respectively. Uterine blood flow response to heat stress in pregnant animals varied among t issues: no changes occurred in the flow to implantation sites (early p regnancy) or to inter-embryonic segments (mid- to late pregnancy); tha t to gestation sacs decreased by 12-40% at the different lactation sta ges; and that to maternal placentas decreased in the lactating state b y 18%, and rose in the non-lactating state by 50%. Results indicate th at pregnancy and lactation modulate vasomotor responses to beat stress in mammary and reproductive tissues, and that the extent of the modul ation depends upon their respective stages. Copyright (C) 1996 Elsevie r Science Inc.