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Conjugation, Distribution, and Biological Half-Life (t ) of Radioactive Progesterone in Plasma and Red Cells of Bovine Blood^{1, 2,}

Department of Dairy Husbandry, University of Missouri, Columbia

ABSTRACT

A study was made of the fate in the blood of labeled progesterone injected intravenously into the bovine. The biological half-lives (t ) of progesterone in the free (ether-extractable) fraction of the plasma of two pregnant cows at the 60th and 180th day of pregnancy were 25.4 and 21.1 min, respectively, averaging 23.3 min. The half-lives and distribution of radioactivity were found to be approximately the same in the red cells as in the plasma.

The conjugated (butanol-extractable) fraction of plasma and cells was determined in the 6-months-pregnant cow. The radioactivity reached a peak within 10 min and disappeared within 45 min. The conjugated radioactivity represented about 10% of the free radioactivity.

The biological half-lives were determined in the plasma free fraction of nine nonpregnant cows. The t 's averaged 36.3 min and varied from 18.8 to 59 min. The difference between the average t values of progesterone for the pregnant and nonpregnant animals is not statistically significant. The average half-life of all eleven animals was found to be 33.8 min.

¹ Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 2628. Approved by the Director.

² Aided in part by a grant from the U.S. Atomic Energy Commission. Contract No. AT (11-1) 301.

³ Postdoctoral Research Fellow of the National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, U. S. Public Health Service.

⁴ Postdoctoral Research Fellow of the Division of General Medical Science, National Institutes of Health, U.S. Public Health Service.

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