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Progestin Levels in Corpora Lutea and Progesterone in Ovarian Venous and Jugular Vein Blood Plasma of the Pregnant Bovine¹

Department of Animal Sciences, Purdue University, Lafayette, Indiana, and Departments of Animal Sciences and Veterinary Clinical Medicine and Surgery, Washington State University, Pullman

ABSTRACT

Progesterone and 20ß-hydroxy-⁴-pregnene-3-one (20ß-ol) were assayed in 125 corpora lutea (CL), 78 ovarian venous blood plasma, and 61 jugular venous blood plasma samples from cows 11 to 284 days after estrus, breeding, or pregnancy. The objective was to evaluate luteal function during pregnancy. Weight of the CL (P < 0.005), progesterone content (P < 0.025), 20ß-ol content (P < 0.01), and concentration (P < 0.05) increased significantly as age of the animal increased, but progesterone concentration did not. Also, CL from Guernsey cows were heavier than CL from Jersey cows (P < 0.01) on an age-adjusted basis. Other breed differences were non-significant.

Progesterone concentration in ovarian vein plasma declined during pregnancy (r = –0.38; P < 0.01), while jugular plasma, levels increased (r = 0.28; P < 0.05). Weight and progesterone content and concentration of the CL did not change significantly (P < 0.25), but content and concentration of 20ß-ol were high at 52 days, then declined and increased to a second peak at 204 days and again declined at 232 and 252 days (P < 0.005).

Weight of the CL was not highly correlated with any of the hormone measurements. The partial correlations (age of animal held constant) between content and concentration of progesterone, 20ß-ol, and total progestin in the CL were 0.87, 0.94, and 0.87 (P < 0.01), respectively. Though CL progesterone and 20ß-ol were significantly correlated (P < 0.01), the relationship was considered too low to use one hormone to predict quantities of the other. Ovarian venous plasma progesterone concentration was correlated with progesterone (r = 0.25; P < 0.05) and progestin (r = 0.23; P < 0.05) content of the CL. No other correlations involving blood plasma progesterone, ovarian or jugular, were significant. Though the CL remains active throughout pregnancy, weight and levels of progesterone of the CL do not reflect the decline in ovarian venous plasma progesterone, the changes in CL 20ß-ol or the increasing levels of progesterone in jugular plasma.

Average ± standard errors for the study were: CL-weight 6.5 ± 0.15 g; progesterone content 199 ± 9.9 µg and concentration 31.1 ± 1.4 µg/g; 20ß-ol content 41.0 ± 3.0 µg and concentration 6.2 ± 0.44 µg/g; and ovarian and jugular venous plasma concentrations 2.9 ± 0.21 µg/ml and 30.3 ± 1.7 ng/ml, respectively. The average age of the animals was 54 ± 2.2 months.

¹ Journal paper no. 3117, Purdue University Agricultural Experiment Station, 47907, Projects 1306 (Indiana) and 1585 (Washington). A contribution from Western Regional Research, Project W-49.

² Department of Animal Sciences, Purdue University.

³ Department of Animal Sciences, Washington State University.

⁴ Present address: Department of Dairy Science, Ohio State University, Columbus.

⁵ Present address: Department of Biochemistry, University of Georgia, Athens.

⁶ Department of Veterinary Clinical Medicine and Surgery, Washington State University.