Androgen Regulation of Molecular Forms of β‐D‐Glucuronidase in the Mouse Epididymis: Comparison With Liver and Kidney

Abstract

ABSTRACT: The expression and androgen regulation of β‐glucuronidase molecular forms were examined in mouse epididymis, liver, and kidney. Two‐dimensional polyacrylamide gel electrophoresis performed under nondenaturing conditions showed that, compared to liver and kidney, which contain four microsomal (M1‐M4) and a major lysosomal (L) form of β‐glucuronidase, the epididymis revealed regional differences and tissue specificity in the expression of the various molecular forms of the enzyme. Only the lysosomal form (pl 5.4–6.1) is present in the caput epididymidis while the corpus/cauda contains the lysosomal form, the free X form (pl 5.9‐6.3) and the four microsomal forms (X form complexed with egasyn). Mutant mice that lack egasyn have no microsomal forms in the distal epididymis. In epididymal fluid, the lysosomal form is found throughout the epididymis, whereas the X form appears only in the corpus/cauda epididymidis. Sodium dodecyl Sulfate (SDS)‐gel electrophoresis and western blot analysis of immunoprecipitated β‐glucuronidase revealed only one band corresponding to the L form (apparent molecular weight 74 kDa) in the caput epididymidis and two bands in the corpus/cauda (apparent molecular weights 73 and 75 kDa), corresponding to L and X forms, respectively. Castration of mice led to the suppression of the regional differences in the appearance of X and M forms in the epididymis. Testosterone supplementation to castrated mice restored the characteristic electrophoretic pattern of β‐glucuronidase in the caput epididymidis. In the liver and kidney, castration has no effect on the expression of the molecular forms, whereas androgen treatment induced the X form in the kidney. Histochemical localization of β‐glucuronidase confirmed the region specificity seen in the epididymis and in addition revealed cell specificity in the expression of β‐glucuronidase. These results indicate that β‐glucuronidase shows tissue specificity and, in the case of the epididymis, region and cell specificity. In addition, the enzyme in the different tissues responds differentially to androgens.