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Functional State of Bovine Corpora Lutea as Determined by De Novo Production of Progesterone in vitro^{1, 2,}

Pennsylvania State University, University Park

Abstract

In two experiments involving a total of 15 nulliparous Holstein heifers, the functional states of corpora lutea at day 14 of the estrual cycle and day 28 of pregnancy were estimated by the de novo progesterone production during in vitro incubation. Two corpora lutea were removed from each animal at the respective reproductive stages via a supra-vaginal incision. Luteal tissue slices (200 mg.) were incubated for 2 hr. in Krebs-Ringer bicarbonate-glucose medium. Incubated and unincubated samples were chemically analyzed for progesterone, and de novo progester-one production was determined.

The average de novo progesterone production for day-28 corpora lutea (68.4 mcg./gm.) was 68.5% higher than for the day-14 corpora lutea (40.6 mcg./gm.). The average within-heifer de novo production difference of 27.8 mcg./gm. for the 15 heifers was significant (P<.001). The average initial progesterone concentration of day-28 corpora lutea (79.3 mcg./gm.) was also significantly (P<.001) higher than the average concentration of day-14 corpora lutea (55.8 mcg./gm.). Although slightly higher, the average weight of the day-28 glands (5.70 gm.) did not differ significantly from the average weight of the day-14 glands (5.32 gm.). These results suggest that the corpus luteum at day 28 of pregnancy is functioning at a higher level than the corpus luteum at day 14 of the estrual cycle.

¹ Authorized for publication as Paper No.3146 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

² The initial experiment reported herein was supported by Training Grant TIAM 5240,Institute of Arthritis and Metabolic Disease, NIH. The second experiment was supported by a research grant from The Lalor Foundation, Wilmington, Delaware.

³ The senior author wishes to express his sincere appreciation to L. E. Casida, Department of Genetics, University of Wisconsin, for his counsel in the design and conduct of the initial experiment.

⁴ Department of Zoology.

⁵ Department of Dairy Science.