Progestin Content of Ovaries and the Effect on Assessment of Luteal Activity in the Bovine

Abstract

Samples of ovarian venous blood and ovaries collected by laparotomy from 114 animals following estrus and breeding, during pregnancy and post-partum, were assayed for the progestins, progesterone and 20β-hydroxy-Δ4-pregnene-3-one (20β-ol). The objective was to determine if progestin content of the corpus luteum (CL) adequately reflected the progestin content of both ovaries. Progestins in ovaries and CL were measured spectrophotometrically, and progesterone in jugular venous plasma was measured by double isotope derivative reaction. Ovarian venous plasma progesterone was measured by both methods. The CL contained 94% of the total progestin in 100 ovaries, bearing a CL of which 80% was progesterone and 14% was 20β-ol. The CL content averaged 214±9.5 µg of progesterone and 38.4±3.2 of 20β-ol. Progesterone and 20β-ol in the residual ovary were not correlated (r = 0.11). The part-whole linear correlations comparing the progestins in CL with total in the ovary ranged from 0.96 to 0.99 for CL content and 0.81 to 0.87 for CL concentrations. The progestins in ovaries without a CL were low and often not detectable and content was not significantly correlated with progestin in the ovary containing a CL (19 pairs of ovaries). Progesterone concentration in the ovarian venous plasma from the CL-bearing ovary was four times higher as compared to plasma from the opposite ovary (P<0.005). No relationships were found between concentration of progesterone in jugular venous plasma and progesterone in ovarian venous plasma and progestin content of the ovary. Progestin content in both ovaries one to four days post-partum was approximately one-tenth the content observed during pregnancy. These data indicate that the progestin content of the CL adequately reflects changes in progestin content of both ovaries in the bovine.