Date of Award
Master of Science
R. N. Heitmann
James K. Miller, Thomas T. Chen
Open, mid- (78-109d) and late- (126-147d) gestating, lactating (7- 35d post partum) and weaning (42-56d post partum) ewes were fitted with catheters in the femoral artery and femoral, portal, hepatic and mesenteric veins to measure net fluxes of glucose, ketones, free fatty acids (FFA), insulin and glucagon across portal-drained viscera (PDV), liver (HEP) and hindquarter tissues. All gestating ewes were singleparous and subsequently, all lactating ewes nursed a single lamb. Blood flow across splanchnic tissues was calculated by measuring down stream dilution of para-aminohippurate (PAH). Hindquarter flow was measured by infusing PAH into the femoral artery and measuring jugular- femoral vein differences. Net fluxes were found by multiplying venoarterial differences by tissue blood flows. Arterial concentrations of glucose decreased from 55 in open ewes to 45, 46 and 46 mg/dl in mid- and late-gestation and lactation, respectively, then returned to control values in weaning ewes without changes in tissue flux. Arterial concentrations of FFA increased from 173 in open ewes to 313, 384 and 223 μM in mid- and late-gestation and lactation undoubtedly due to increased PDV release from 3 in open ewes to 28, 31 and 14 μmol/min and hindquarter release from 7 in open ewes to 44, 29 and 20 μmol/min and despite increased HEP uptake from 36 in open ewes to 93, 102 and 53 μmol/min, respectively. FFA concentrations in the artery decreased from 173 in open ewes to 101 μM in weaning ewes due to decreased PDV release from 3 in open ewes to -8 μmol/min and despite decreased HEP uptake from 36 in open ewes to 13 μmol/min. Arterial concentration of aceteacetate increased in lactation and weaning from 29 in open ewes to 47 and 37 μM perhaps due to increased PDV production from 44 in open ewes to 61 and 62 μmol/min, respectively. Arterial concentration of 3-hydroxybutyrate increased from 563 in open ewes to 739, 836, 963 and 1118 μM in mid- and late-gestation, lactation and weaning, respectively, due to increased HEP release in mid- and late-gestation from 226 in open ewes to 362 and 557 μmol/min and increased PDV release in lactation and weaning from 270 in open ewes to 343 and 412 μmol/min and despite increased hindquarter uptake in lactation and weaning from -110 in open ewes to -268 and -197 μmol/min, respectively. Arterial concentration of insulin decreased from 72 in open ewes to 45, 32, 19 and 33 μU/ml in mid- and late-gestation, lactation and weaning due to decreased PDV production from 29 in open ewes to 15, 16, 7 and 22 μU/min, respectively. Arterial concentration of glucagon increased from 195 in open ewes to 260 μ/ml in late gestation due to increased PDV production from 4.2 in open ewes to 5.3 μg\h. Insulin to glucagon ratio decreased from 9.4 in open ewes to 6.5, 2.7, 2.1 and 3.5 in mid- and late-gestation, lactation and weaning primarily due to decreased insulin concentrations concomitant with relatively unchanged glucagon concentrations. Glucose and insulin decreased concomitantly in mid- and late-gestation and lactation favoring increased PDV and hindquarter FFA release and hepatic uptake and subsequent increased hepatic ketogenesis resulting in increased ketone concentrations. Therefore, FFA and ketones may be used as alternate energy fuels sparing glucose for increased utero-placental- fetal and mammary tissue utilization.
Sensenig, Scott Charles, "Energy metabolite and glucoregulatory hormone concentrations and net fluxes across portal-drained viscera, hepatic, total splanchnic and peripheral tissues in gestating, lactating and weaning ewes. " Master's Thesis, University of Tennessee, 1987.