Profiles of uterine protein in flushings and progesterone in plasma of normal and repeat-breeding dairy cattle.

Uterine secretions were collected nonsurgically from 15 normal and 9 repeat-breeder Holstein and Jersey cows on d 0 and 5, 10, or 15 of an estrous cycle. Uterine flushings presented 19 protein bands in one-dimensional PAGE, but only 16 bands were found in gels of plasma samples of normal and repeat-breeder cows. Red blood cell contamination of uterine flushings ranged from 50,400 to 4,940,000 cells/ml of flush recovered for visibly clear samples to over 17 x 10(6) cells/ml in obviously red samples. A prealbumin (electrophoretic mobility relative to albumin; Ra 1.28) and a pretransferrin (Ra .72) were found in uterine flushings. A possible uterine protein (Ra .35) was probably a hemoglobin-like contaminant. Data suggest that differences in peripheral plasma progesterone concentrations during the estrous cycle in repeat-breeder cattle may provide the basis for altered synthesis or secretion of uterine proteins needed for development by early embryos.