Relation Between Luteal Regression and So-called Counter Current Mechanism in the Cow: Verification from PGF_2α Concentrations in Ovarian Arterial, Uterine Venous and Jugular Venous Blood following PGF_2α Loading

Abstract

Diffusion into the ovarian artery of prostaglandin F_2α (PGF_2α) infused into the uterine vein of a cow was studied to demonstrate the existence of the so-called “utero-ovarian counter current mechanism” which was responsible for luteal regression in sheep and guinea pigs. In the first part of Exp. 1, PGF_2α was infused in the uterine vein through an indwelling cannula. The plasma PGF_2α concentration in the ovarian artery was increased to more than 300 times that in the jugular vein 1 min after the start of injection. In the second part which was begun 15 min after the completion of final blood sampling in the first part the plasma PGF_2α concentration in the ovarian artery was increased to 2.7 times that in the jugular vein one minute after the start of injection. Though the difference between the PGF_2α concentrations in the arterial and venous blood was smaller in the second part of Exp. 1, these results clearly show the existence of the counter current mechanism in the cow. In Experiment 2, PGF_2α (15 mg in 3 ml solvent) was injected into the gluteal muscle 30 min after the completion of the final blood sampling to examine the changes in plasma concentrations of PGF_2α in the ovarian artery, jugular vein and uterine vein after systemic injection of PGF_2α. The PGF_2α concentration in uterine venous blood prior to intra-gluteal injection was extremely high (60000 pg/ml). The concentrations in the ovarian artery and jugular vein were slightly increased with time after injection. Although the value was somewhat higher in the ovarian artery, almost similar patterns of change were seen in both the ovarian artery and the jugular vein.