title: Kinetics of splanchnic progesterone metabolism in ewes fed two levels of nutrition.
abstract: The objective of this study was to determine whether chronic nutritional treatment influences progesterone (P4) metabolism by splanchnic tissues and to develop a mathematical model of P4 metabolism in ewes. Five ovariectomized (ovx), multiparous ewes were assigned to a high feed intake and five multiparous ovx ewes were assigned to a low feed intake. The ewes with high feed intake received daily ME intakes of 99 kcal/BWkg.75, and the ewes with low intake received daily ME intakes of 63 kcal/BWkg.75. Catheters were placed surgically in the abdominal aorta, the portal vein, a branch of the hepatic vein, and a mesenteric vein. Blood and plasma flows across visceral organs were determined by marker dilution (p-aminohippuric acid), and P4 was determined with a RIA. The net splanchnic P4 flux and oxygen (O2) consumption were determined during five rates of P4 infusion into the jugular vein (112, 224, 449, 897, and 1,795 micrograms/h). Splanchnic O2 consumption was greater (P = .05) in the ewes with high feed intake. Net splanchnic P4 flux did not differ (P > .10) between nutritional treatments. The correlation between net splanchnic P4 flux and O2 consumption did not differ from zero (P = .69). Net splanchnic P4 flux was related linearly to plasma arterial P4 concentration. Splanchnic tissue clearance rate was 18% of the infusion rate. The behavior of the P4 model indicates that whole-body P4 metabolism is the sum of first-order kinetic reactions. The data indicate that splanchnic clearance of P4 is not affected by nutritional status.
authors.affiliation: U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933.
authors.forename: H C
authors.initials: HC
authors.lastname: Freetly
authors.forename: C L
authors.initials: CL
authors.lastname: Ferrell
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D005260:Female; D016018:Least-Squares Analysis; D016014:Linear Models; D008099:Liver / Q000378:metabolism; D010052:Ovariectomy / Q000662:veterinary; D010101:Oxygen Consumption; D011374:Progesterone / Q000378:metabolism*; D012039:Regional Blood Flow; D012756:Sheep / Q000378:metabolism*; D013152:Splanchnic Circulation / Q000502:physiology; D014781:Viscera / Q000378:metabolism*
chemical_list: D011374:Progesterone