LOCALIZATION AND MOLECULAR HETEROGENEITY OF SULFATED GLYCOPROTEIN-2 (CLUSTERIN) AMONG VENTRAL PROSTATE, SEMINAL-VESICLE, TESTIS, AND EPIDIDYMIS OF RATS

In the rat reproductive tract, sulfated glycoprotein 2 (SGP-2) is pres ent in the ventral prostate, seminal vesicle, testis, and epididymis. In the ventral prostate, SGP-2 is associated with the process of progr ammed cell death, while in the testis and epididymis a role for SGP-2 in sperm maturation has been proposed. Available information suggests that there are both inter- and intra-organ variations in SGP-2 localiz ation, molecular forms, and response to androgen ablation. In the pres ent study, localization of SGP-2 within the ventral prostate, seminal vesicle, and epididymis was compared by immunohistochemistry. In the v entral prostate of intact rats, immunoreactive SGP-2 was confined to a discrete population of epithelial cells lining the proximal ducts. Ep ithelial cells in other regions of the ventral prostate did not stain for SGP-2. A similar staining pattern was observed for the seminal ves icle; a small population of SGP-2-expressing epithelial cells was foun d in epithelium that did not stain for SGP-2. The epididymis also demo nstrated a non-uniform staining pattern. The caput displayed strong im munoperoxidase reaction over the apical membrane and stereocilia of al l principal cells. Principal cells also showed variable degrees of cyt oplasmic staining ranging from weak to strongly positive. The corpus a nd cauda showed a similar staining pattern. After castration, all epit helial cells in the ventral prostate and seminal vesicle became intens ely positive for SGP-2 staining. In the caput and cauda epididymis the re was an increase in the number of principal cells demonstrating stro ng intracellular staining for SGP-2. These results suggest that as obs erved previously in the regressing ventral prostate, increased intrace llular SGP-2 staining may also be associated with the regressing epidi dymis and seminal vesicle. Differences in molecular forms of SGP-2 wer e investigated by two-dimensional Western and lectin blots. Molecular forms of SGP-2 differed between testis and epididymis but were similar between ventral prostate and seminal vesicle. Prostate and seminal ve sicle forms of SGP-2 differed from those of both testis and epididymis . Analysis of terminal carbohydrate present on the various SGP-2 molec ular forms also confirmed the existence of heterogeneity. These result s demonstrate the presence of multiple molecular forms of SGP-2 in var ious organs of the male reproductive tract in rats and suggest a possi ble variation in functional activity and/or half-life of SGP-2 in thes e organs.