McPherson, F., Nielsen, S., and Chenoweth, P. (2012) Sperm factors influencing sow insemination outcomes. Reproduction in Domestic Animals, 47 (Supplement 4). p. 610.

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Abstract

Sulfonated steroids (sSt) are traditionally regarded as inactive metabolites but have recently gained increasing interest as a potential pool of precursors which may enter the synthesis of active free steroids (fSt) by the activity of steroid sulfatase (StS). Due to its remarkably high production of sulfonated estrone (E1S) and dehydroepiandrosterone (DHEAS), the porcine testicular-epididymal compartment (pTEC) may be a useful model to gain further insight in the metabolism, transport and function of sSt. Expression of relevant genes was measured by real-time RT-PCR in five sexually mature boars at the following localizations: testis (TE), epididymal head (proximal and distal segment, EH1-2), epididymal body (four segments, EB1-4), epididymal tail (ET1-2) and deferent duct (DD). Expression of the steroidogenic enzymes CYP11A1, CYP17, CYP19 and HSD17B3 was virtually restricted to TE. Expression of HSD3B was only low in TE (median: 11.9 relative units) and EH1, increased gradually from EH2 to ET1 and was highest in ET2 (median: 244 R.U.). Substantial StS expression was detected from TE to DD with the exception of EB1-4. A similar expression pattern was found for the sSt transporter candidate SLC10A6. The sulfotransferases (SULTs) 1A1 (phenol preferring) and 1E1 (estrogen preferring) were predominantly expressed in EH1-2 and DD, whereas only minimal expression was detected in TE. Different from SULT2A1 (DHEA preferring), which was highly expressed in TE, the cholesterol and pregnenolone preferring SULT2B1 was predominantly localized in ET2 and DD. Expression patterns of StS and of the SULTs 1E1, 2A1 and 2B1 were basically confirmed on the protein level by immunohistochemistry. Despite low RGE values for HSD3B in TE, testosterone (T) concentrations in testicular superficial veins (tSV) as measured by liquid chromatography-tandem mass spectrometry were 20 to 30-fold higher compared to concentrations in testicular artery and systemic circulation confirming a significant T output from TE. Although gene expression data suggest that the epididymis is the major site of HSD3B expression in the pTEC and thus may provide 3-keto-4-ene precursors for T synthesis in Leydig cells, corresponding measurements showed a substantial efflux of androstenedione in tSV indicating testicular origin. Despite the virtual absence of SULT1E1 in TE, also a high efflux of E1S was measured in tSV challenging the role of this SULT as the major enzyme catalyzing the sulfonation of testicular estrogens in boars. In conclusion, the results suggest that in boars the epididymis and DD exhibit a significant steroid metabolic activity and challenge the current concept of the testis as the sole organ encompassing the whole machinery for T and E1S synthesis in boars.

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