Haemodynamic and catecholamine responses to hypothermia in the fetal sheep in utero.
Chronically catheterised fetal sheep (117-134 days) were cooled in utero via a tubing coil placed around the fetal trunk through which cold water was circulated for one hour. The fetal core temperature was reduced by 5.51 +/- 0.61 degrees C. This hypothermia was associated with tachycardia (P less than 0.001) and hypertension (P less than 0.001) (n = 12). The tachycardia was abolished by treatment with propranolol (n = 4) and the hypertension by treatment with phentolamine (n = 5). Blood flow in the left umbilical artery was measured by an electromagnetic flow probe in 4 fetuses and rose (P less than 0.001) with fetal cooling. The increase in blood flow was abolished by treatment with either phentolamine or propranolol. These observations are consistent with a redistribution of fetal blood flow from peripheral tissues to placental and thermogenic tissues during cooling. Fetal plasma adrenaline and noradrenaline concentrations rose (P less than 0.01) during fetal cooling (n = 5). These studies demonstrate that catecholamine and cardiovascular responses to environmental hypothermia have differentiated prior to birth in the sheep fetus.
D000818:Animals; D002320:Cardiovascular Physiological Phenomena; D004837:Epinephrine / Q000097:blood*; D005260:Female; D005333:Fetus / Q000378:metabolism / Q000502:physiology*; D006439:Hemodynamics; D007035:Hypothermia / Q000097:blood / Q000196:embryology / Q000503:physiopathology*; D009638:Norepinephrine / Q000097:blood*; D011247:Pregnancy; D012756:Sheep / Q000196:embryology; D013565:Sympatholytics / Q000494:pharmacology
D013565:Sympatholytics; D009638:Norepinephrine; D004837:Epinephrine