Biochemical studies of intrauterine components of the tammar wallaby Macropus eugenii during pregnancy.

The in vitro uptake and incorporation of [H]ui idine by blastocysts of the tammar wallaby showed a 16and 30-fold increase from day 0 to day 10 after removal of pouch young, respectively. Two of the six non-expanded blastocysts recovered on day 5 showed a tenfold increase in incorporation. During the first ten days after removal of pouch young the diameter of the blastocyst increased threefold. Endometrial exudate from gravid uteri had a higher protein concentration than exudate from nongravid uteri (39-5±0-9 and 320± 2-0 mg/ml (mean + S.E.M.), respectively). Endometrial exudates from uteri where the blastocyst was actively growing were found to contain six uterine-specific proteins. These were separated by gradient polyacrylamide gel electrophoresis. Two of the proteins were prealbumins and the others were larger molecules (M.W. 153000-670000). Two proteins were only present at particular stages of pregnancy: the other four were present at all stages from diapause to birth, in exudate from gravid and nongravid uteri. The specific binding of progesterone and androstenedione to proteins in endometrial exudates or uterine flushings from pregnant wallabies was less than one per cent of the value obtained from day-5 pregnant rabbits. The ability of mouse blastocysts to take up and incorporate [H]uridine into acidinsoluble material increased threefold in the presence of day-10 endometrial exudates from wallabies. However, this was less than ten percent of the values obtained in the presence of bovine serum albumin. The concentration of calcium in endometrial exudates increased from 23-6 to 45-2/*g/ml during pregnancy; in endometrium it remained at 88-7/*g/g (wet weight) throughout pregnancy, and in plasma it was 53-3/Mg/ml. The concentration of zinc in endometrial exudates was 4-5/fg/ml; in endometrium it decreased from 21-8 to 13-3/^g/g (wet weight) during pregnancy and in plasma it was 0-6 /*g/ml.