Net uptakes of oestradiol-17 beta and progesterone across the portal-drained viscera and the liver of ewes

Abstract

The objective of this study was to determine whether circulating concentrations or prior exposure to estradiol-17 beta (OE2) and progesterone affected their uptake by splanchnic tissues. Catheters were surgically placed in the portal vein, a branch of the hepatic vein, a mesenteric vein and the abdominal aorta of three multiparous ovariectomized Dorset ewes. Blood and plasma flow across the portal-drained viscera (PDV) and the liver, and net uptake of OE2 and O2 consumption in these same tissues were determined in ovariectomized ewes (control), during OE2 infusion into the jugular vein, 7 days after an OE2 implant had been given, and during OE2 infusion into the jugular vein 7 days after an OE2 implant. The above treatments were repeated for progesterone. Plasma flows across visceral organs were determined by marker dilution (para-aminohippuric acid), and OE2 and progesterone concentrations were determined by radioimmunoassay. During the infusion with OE2, OE2 arterial concentration (mean +/- S.D.) was 346 +/- 199 pg/ml, PDV net uptake was 9.7 +/- 5.6 micrograms OE2/h and hepatic net uptake was 15.5 +/- 9.5 micrograms OE2/h. Hepatic uptake was 82% of the jugular OE2 infusion rate. Blood flow and oxygen consumption by hepatic tissue increased when ewes were exposed to an OE2 implant for 7 days. During the infusion with progesterone, progesterone arterial concentration (mean +/- S.D.) was 8.8 +/- 3.4 ng/ml, PDV net uptake was 220 +/- 118 micrograms progesterone/h and hepatic net uptake was 238 +/- 52 micrograms progesterone/h. Hepatic net uptake was 23% of the progesterone jugular infusion rate.