Blood Flow, Steroid Secretion and Nutrient Uptake of the Gravid Bovine Uterus and Fetus2

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Abstract
A study was conducted with mature Hereford cows to quantitate blood flow, steroid secretion and nutrient uptake of the gravid uterus and fetus. Surgery was performed on cows at 163 to 166 (stage 1, N = 5) and 173 to 176 (stage 2, N = 11) d postmating. The uterus of each cow was exposed by midventral laparotomy and catheters were placed in a major branch of an artery (UA) and vein (UV) of the gravid uterine horn, an umbilical vein (UMV) and a fetal femoral artery (FA) and vein (FV). Samples were taken daily from the UA, UV, UMV and FA catheters. Plasma was frozen and later assayed for α-amino N (AN), urea N (UN), glucose (G), estrone (E1), estradiol-17β (E2β) and progesterone (P4). Blood flow was estimated by the steady state diffusion method using antipyrine as the test substance on about d 7 postsurgery. Antipyrine, G, lactate (L) and O2 concentrations were determined in blood collected during this procedure. Concentrations of E1 and E2β were greater (P<.05) in UV than in UA plasma, but these differences were reduced from stage 1 to stage 2. The UA and UV plasma concentrations of E1 were greater (P<.05) than those of E2β across both stages of gestation (31 ± 3 vs l6 ± l and 72 ± 11 vs 25 ± 4 pg/ml, respectively). In contrast, E2β concentrations were greater (P<.05) than E1 in UMV and FA plasma (20 ± 3 vs 12 ± 2 and 22 ± 2 vs 12 ± 1 pg/ml, respectively). Concentrations of E1. and E2β in UMV plasma were equal to or greater than in FA plasma of stage 1 cows (14 ± 4 and 27 ± 3 vs 11 ± 2 and 20 ± 3 pg/ml, respectively). Stage 2 cows, however, had greater (P<.05) E2β concentrations in FA than UMV plasma (23 ± 3 vs 13 ± 2 pg/ml) while E1 concentrations in FA plasma were similar to those in UMV plasma (12 ± l vs 9 ± l pg/ml). Regardless of stage of gestation, P4 concentrations in UA were greater (P<.05) than in UV plasma (7.01 ± .94 vs 4.38 ± .42 ng/ml) while concentrations of P4 in UMV (.21 ± .04 ng/ml) and FA plasma (.18 ± .05 ng/ml) approached the lower limits of assay sensitivity. These data suggest the bovine fetus maintained constant levels of E2β despite decreased E2β concentrations in UMV plasma. Mean uterine and umbilical blood flows were 5,954 ± 518 and 1,107 ± 44 ml/min, respectively. Net uptake of AN, UN, G, L and O2 by the gravid uterus was 1.17 ± .11 meq/min, —.408 ± .037 meq/min, .748 ± .093 mmol/min, —.186 ± .017 mmol/min and 4.04 ± .19 mmol/min, respectively. Net fetal uptake of each of these metabolites was .184 ± .007 meq/min, —.099 ± .004 meq/min, .130 ± .022 :nmol/min, .192 ± .048 mmol/min and 1.158 ± .087 mmol/min, respectively. These data indicated a net uptake of AN, G and O2, and a net loss of UN by the fetus and gravid uterus, and indicated a net flux of lactate from the utero-placental unit to both the maternal and fetal circulations. Copyright © 1983. American Society of Animal Science . Copyright 1983 by American Society of Animal Science.

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