Uterine luminal proteins in the cycling mare

Abstract

Qualitative changes in the protein content of mare uterine flushings were determined on Days 4, 8, 12, 14, 16, 18 and 20 postovulation. Acid phosphatase and leucine aminopeptidase enzymatic activities were also determined for these treatment days. All collections were obtained using a nonsurgical, transcervical technique. Sephadex G-200 column chromatography indicated that 5 distinct protein fractions existed for all days tested. The chromatographic mobility (K(av)) of these fractions did not change during the estrous cycle. When expressed as percentage of the total protein, peaks I, IV and V were significantly affected (P<0.005, 0.05 and 0.025, respectively) by day of the estrous cycle, whereas, peaks II and III were not. Acid phosphatase activity was significantly affected P<0.05) by day of the estrous cycle and maximal values were found in the late luteal phase. Mean values ranged from 10 to 193 μM of inorganic phosphate released per h on Days 4 and 18, respectively, followed by a rapid decline on Day 20. Sephadex G-200 studies indicated that the acid phosphatase enzymatic activity was associated with low molecular weight fractions III and IV and, therefore, was probably nonlysosomal in origin. Leucine aminopeptidase activity was maximal in the midluteal phase (Day 12) and was significantly affected (P<0.005) by day of the estrous cycle. Sephadex G-200 chromatography indicated that this enzyme was associated with high molecular weight fractions I and II. Over the course of this study a purple-colored protein was found in the uterine flushing of a pseudopregnant mare. Biochemical and immunological examinations indicated that similar properties existed for the equine purple protein and the porcine purple protein, previously described by Schlosnagle et al. (1974).