Steroid sulfotransferases in the porcine testis and epididymis (subproject 3, DFG research group 1369 “Sulfated Steroids in Reproduction”)

In adult boars high levels of various sulfated steroids have been determined with maximum concentrations in the systemic circulation up to 150 ng/ml for dehydroepiandrosterone sulfate (DHEAS), 45 ng/ml for estrone sulfate (E1S) and 20 ng/ml for pregnenolone sulfate (P5S). Measurements in the testicular circulation clearly indicate that they mainly originate from the testis. In order to obtain further information on their formation, the expression of sulfotransferases (SULTs) considered relevant for the sulfation of estrogens (SULT1E1), DHEA (SULT2A1) and of P5 and cholesterol (SULT2B1) was investigated on the mRNA (SULTs 1E1, 2A1 and 2B1) and the protein level (SULTs 1E1 and 2B1) in the porcine testis and epididymis applying real-time RT-PCR, western blot and immunohistochemistry (IHC). Moreover, sulfation of E1, DHEA and P5 was assessed in an in vitro assay using cytosolic fractions in the presence of 3′-phosphoadenosine-5′-phosphosulfate. Relative gene expression (RGE) levels of SULT1E1 were high in the epididymal head (EH), decreased gradually in the epididymal body (EB) and tail (ET) but were at the limit of detection in the testis. Corresponding results were obtained from IHC and determinations of enzyme activity. RGE levels for SULT2B1 were minimal in the testis and EH, increased gradually in EB and were maximal in the hind part of ET. In the epididymis this expression pattern was consistent with sulfation of P5 and with cytosolic immunostaining in epithelial cells. However, in the EH epithelium and in various cell types of the testis distinct nuclear signals occurred in the absence of sulfation of P5. RGE levels of SULT2A1-mRNA were high in the testis and variable in the epididymis. However, sulfation of DHEA was virtually undetectable. The release of high amounts of steroid sulfates from the porcine testis in the virtual absence of relevant sulfotransferase activities remains unclear but might be explained by the extensive utilization of sulfated precursors.