Appearance of β-hexosaminidase and other lysosomal-like enzymes in the uterine lumen of gilts, ewes and mares in response to progesterone and oestrogens

Abstract

In one experiment, ovariectomized gilts were treated with corn oil (vehicle), progesterone, oestradiol-17β or both steroids. While oestradiol treatment did not stimulate enzyme activity in uterine flushings relative to vehicle-treated animals, gilts treated with progesterone had elevated amounts of all enzymes measured. Progesterone was less effective when co-administered with oestradiol-17β. Enzymes were not equally stimulated by progesterone. For example, there was a 909-fold increase in acid phosphatase activity in uterine flushings and a 304-fold increase in β-N-acetylglucosaminidase, but only a 10-fold increase in β-glucosidase. Endometrial explants from gilts synthesized and secreted radiolabelled β-N-acetylglucosaminidase, suggesting that at least some lysosomal enzymes enter the uterus through secretory processes. In other experiments, changes in β-N-acetylglucosaminidase in uterine fluids of mares and ewes treated with hormonal regimens similar to those given to the gilts were evaluated. Treatment with the combination of progesterone and oestrogen stimulated accumulation of the enzyme relative to that in vehicle-treated animals. The biochemical properties of porcine β-N-acetylglucosaminidase were examined in detail. Properties of the uterine enzyme were similar to reported values for lysosomal hexosaminidase. These included molecular weight (82,000-89,000), pH optimum (pH 4.4), presence of two isomers (isolectric points of 5.5 and 8.0) and ability to hydrolyse substrates for glucosaminidase and galactosaminidase. We conclude that steroids induce the accumulation of lysosomal enzymes in the uterine lumen. The degree of stimulation differed between enzymes, suggesting that those enzymes stimulated to the greatest extent may play an important role in pregnancy.