DEVELOPMENTAL EXPRESSION OF THE GLUTATHIONE-S-TRANSFERASE YO SUBUNIT IN THE RAT TESTIS AND EPIDIDYMIS USING LIGHT-MICROSCOPE IMMUNOCYTOCHEMISTRY

Background: Glutathione S-transferases (GSTs) are a family of isozymes that catalyze the conjugation of glutathione with various toxic elect rophilic compounds. GSTs are composed of several classes based on the degree of sequence homology of their subunits. The Yo subunit, a membe r of the mu class, is expressed at high levels in the testis and epidi dymis. The purpose of this study was to immunolocalize the GST-Yo in t hese tissues during development. Methods: The testes and epididymides of rats aged 7, 15, 21, 28, 39, 42, 45, 49, and 56 days were fixed in Bouin's fixative, and immunostained for light microscopic analysis. Re sults: In the testis the cytoplasm of all germ cells was unreactive un til day 39. At that time, step 18 spermatids appeared moderately react ive, while the few observed step 19 spermatids were intensely reactive as were their residual bodies. The presence of residual bodies indica tes that spermiation takes place as early as day 39; however, the numb er of step 19 spermatids is low at this age. A progressive increase in the size of the tubule and number of elongating spermatids was seen b etween days 42 and 49. In addition, by day 49, a weak staining was obs erved in steps 12-15, moderate in steps 16-17, and intense in steps 18 -19 spermatids. In terms of the intensity of staining, cell types stai ned, size of the tubules, and number of elongating spermatids, no diff erence was noted between day 49, 56, and adult animals. Thus Yo protei n expression in germ cells reached maturity by day 49. The epithelial cells of the rete testis were intensely reactive at day 7 and remained so throughout development. In contrast, while the epithelial cells of the efferent ducts at day 7 were intensely reactive, they were weakly reactive by day 39 and remained so at later ages. Along the entire ep ididymis, the columnar epithelial cells showed a moderate apical/supra nuclear reaction from day 7 to 28. By day 39 principal cells of the in itial segment became weakly reactive, while those in the caput and cor pus were moderately stained, a situation seen at later ages including adults. Only by day 49 did principal cells of the proximal cauda becom e moderately stained as seen in adult animals. Thus the expression of the Yo protein in the principal cells of the proximal cauda may be reg ulated by different factors than those of the caput and corpus epididy midis. Alternatively, the expression of the Yo subunit in principal ce lls of the proximal cauda may develop later since this region would be the last to receive luminally derived testicular products. In the ini tial segment, the decrease in staining of principal cells at day 39 ma y be due to an inhibiting factor emanating from the testis. Spermatozo a appeared in the lumen of each epididymal region well after the expre ssion of Yo had reached its adult staining pattern indicating that the y are not a factor. Conclusions: Overall these results suggest that th e expression of GST-Yo in the various cells of the testis and epididym is are controlled by different factors during postnatal development. ( C) 1994 Wiley-Liss, Inc.