Endogenous estradiol-17beta in bovine tissues

The development of an assay for the estrogen estradiol-17beta in bovine muscle, kidney, liver, and uterine endometrium is described in this report. The tissue was homogenized, extracted, partitioned, and subjected to routine radioimmunoassay. Chromatography was not used. The first part of the report presents data on the accuracy, reproducibility, and sensitivity of the assay. The concentration of estradiol-17beta in the tissues compared with muscle was ranked as follows: uterine endometrium (10-fold higher), liver (3-fold), and kidney (3-fold). The estrogen concentration was not significantly different in the muscle between heifers, but was significantly greater (P less than 0.05) in the liver and kidney of heifers and steers. In heifers pre- and post-estrous phase endometrium (a target tissue of E2beta) contained significantly greater concentrations of estradiol-17beta than did luteal phase endometrium (P less than 0.05), but mean levels in the edible tissues were not significantly different (P greater than 0.05) between these 2 of the 4 stages of the estrous cycle.