DEVELOPMENTAL EXPRESSION OF THE YF-SUBUNIT OF GLUTATHIONE-S-TRANSFERASE-P IN EPITHELIAL-CELLS OF THE TESTIS, EFFERENT DUCTS, AND EPIDIDYMISOF THE RAT

Background: Glutathione S-transferases (GSTs) are a family of isozymes that catalyze the conjugation of the tripeptide, glutathione, to vari ous electrophilic compounds. The major GST in the pi class is GST-P, a homodimer of the Yf subunit, also known as Yp or rat subunit 7. This subunit is found in high concentrations in the epididymis and has rece ntly been immunolocalized within epithelial principal and basal cells of the epididymis. Methods: In the present study we examine in groups of animals fixed in Bouin's fixative for light microscopy and in 4% pa raformaldehyde and 0.5% glutaraldehyde in phosphate buffer for electro n microscopy, the pattern of immunostaining for the Yf subunit of GST- P in the testis, efferent ducts and epididymis at various ages after b irth. Results: In the epididymis, on postnatal days 7 and 15, an immun operoxidase reaction was localized exclusively to the apical and supra nuclear regions of the undifferentiated columnar epithelial cells of t he entire epididymis. By day 21, a dramatic change had taken place. In the initial segment, intermediate zone and proximal caput epididymidi s, the columnar cells showed a distinct checkerboard-like staining pat tern with cells ranging from being intensely reactive to unreactive. I n contrast, principal cells of the distal caput, corpus, and proximal cauda epididymidis were weakly reactive. By day 28 the ratio of reacti ve to unreactive cells in the initial segment, intermediate zone, and proximal caput epididymidis was higher. By day 39, the differentiated columnar epithelial cells, referred to as principal cells, took on the ir adult staining pattern in the proximal and middle areas of the init ial segment as well as the corpus and proximal cauda epididymidis wher e they were slightly reactive; in the distal initial segment they were strongly reactive. At day 49, principal cells in the intermediate zon e and proximal caput became intensely reactive, while showing a distin ct checkerboard-like staining pattern in the distal caput; similar obs ervations were made for tissues taken from 56 and 90-day-old animals. Basal cells also showed a variable staining pattern in the different e pididymal regions as a function of age. At day 21, when they first app eared, they were unreactive except for an occasional reactive cell in the corpus region. At day 28, only in the corpus epididymidis were man y basal cells seen to be reactive. By day 39 the more numerous basal c ells of the corpus and proximal cauda epididymidis were intensely reac tive and remained so into adulthood. In these regions, basal cells app eared as dome-shaped cells (days 21, 28, 39), but then gradually flatt ened out and exhibited processes (days, 49, 56, adults) which collecti vely appeared to envelop the base of each tubule in a mesh-like networ k. The change in basal cell shape in each region coincided with the ar rival of fluid and spermatozoa into the lumen (corpus day 49, proximal cauda day 56). In other epididymal regions, basal cells at day 28 wer e mostly unreactive. However, there was a gradual increase in the numb er of reactive basal cells of these regions between day 39 and 56. Con clusions: The present results thus demonstrate a dramatic change in th e immunostaining pattern for the Yf subunit of GST-P during postnatal development for both principal and basal cells along the epididymis. S uch results suggest that different factors play a role in the regulati on of the expression of the Yf protein, not only in different epididym al regions, but also in different cell types during postnatal developm ent. (C) 1994 Wiley-Liss, Inc.