Evidence for the regulation of beta-N-acetylhexosaminidase expression during pregnancy in the rat

It is believed that the lysosomal glycohydrolase beta-N-acetylhexosaminidas e plays a part in several important processes of reproduction and it has be en postulated that this enzyme is subject to hormonal regulation. During pr egnancy, activity levels of the enzyme are strongly increased in both human and rat serum. However. little is known about the expression of this enzym e in the female reproductive apparatus and there is no evidence linking the production of hexosaminidase alpha- and beta-subunits to pregnancy. To cla rify these aspects better. we examined the enzyme activity, isoenzyme subun it composition and distribution, as well as steady state levels of alpha- a nd beta-subunit mRNAs in the female reproductive organs and in other select ed tissues of pregnant and non-pregnant rats. Among the female rat tissues tested, the ovary and kidney had the highest specific activity. Pregnancy m odulated the hexosaminidase activity differently in the tissues examined. I n pregnant rats, the activity decreased in the ovary but increased signific antly in the uterus, liver and to a lesser extent in other tissues. The dec reased hexosaminidase activity in the ovary from pregnant rats appeared to be accompanied by a disproportionately large decrease in beta-subunit mRNA abundance, whereas in the uterus and liver, an increased abundance of this transcript was detectable. The abundance of alpha-subunit mRNA was comparab le in pregnant and control rat tissues. Hexosaminidase histochemical staini ng of tissue sections clearly demonstrates that the greatly increased activ ity of hexosaminidase in the uterus during pregnancy is largely due to the enzyme in the endometrium. and not to the uterus as a whole. The overall re sults provide evidence that, during pregnancy, a mechanism(s) of regulation of beta-N-acetylhexosaminidase expression is in operation, and that the en zyme is differentially regulated in rat tissues. (C) 2000 Elsevier Science B.V. All rights reserved.