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Relationship of the Hormone-Sensitive Lipase-Mediated Modulation of Cholesterol Metabolism in Individual Compartments of the Testis to Serum Pituitary Hormone and Testosterone Concentrations in a Seasonal Breeder, the Mink (Mustela vison)¹

^a Département de pathologie et biologie cellulaire, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada H3T 1J4 ^b Department of Cell and Molecular Biology, Lund University, Lund, Sweden ^c Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209

The role of cholesterol differs in the two compartments of the testis. In the interstitial tissue, cholesterol is necessary for the synthesis of testosterone, whereas in the seminiferous tubules, membrane cholesterol content in developing germ cells will influence the gametes' fertility. Here we evaluate the hormone-sensitive lipase (HSL) modulation of the cholesterol metabolism in each compartment of the testis. Two HSL immunoreactive bands of 104- and 108-kDa were detected in Western blots performed with polyclonal anti-human HSL antibodies in the interstitial tissue (ITf)- and seminiferous tubule (STf)-enriched fractions generated from testes harvested at 30-day intervals during puberty and, in the adult mink, during the annual seasonal reproductive cycle. Epididymal spermatozoa expressed a 104-kDa HSL isoform, and HSL was active in these cells. Immunolabeling localized HSL to interstitial macrophages; Sertoli cells, where its distribution was stage specific; spermatids; and the equatorial segment of spermatozoa. Total HSL protein levels, specific enzymatic activity, and free cholesterol (FC):esterified cholesterol (EC) ratios varied concomitantly in STf and ITf and reached maximal values in the adult during the period of maximal spermatogenic activity. In STf, HSL-specific activity correlated with FC:EC ratios but not with triglyceride levels. In STf, high HSL-specific activity occurred concomitantly with high FSH serum levels. In ITf, HSL-specific activity was high during periods of low serum prolactin levels and high serum testosterone levels. The results suggest that 1) modulation of cholesterol metabolism in individual testicular compartments may be regulated by HSL isoforms expressed by distinct cells; 2) interstitial macrophages may be part of a system involved in the synthesis of steroid hormones and in the recycling of sterols in the interstitium, whereas in the tubules, recycling could be ensured by Sertoli cells; 3) there is distinctive substrate preference for testicular HSL; and 4) HSL may be the only cholesterol esterase in this location.

¹ This work was supported in part by NSERC grant OGP0041653 to R.M.P., by NSERC grant OGP0194652 to M.L.V., and by Swedish Research Council grant 11284 to C.H. M.L.V. is also funded by scholarships from fonds de la Recherche en santé du Québec.

² Correspondence: R.-Marc Pelletier, Département de pathologie et biologie cellulaire, Faculté de Médecine, Université de Montréal, 2900 Édouard-Montpetit, Montréal, QC, Canada H3T 1J4. FAX: 514 485 7932; e-mail: marc.pelletier{at}umontreal.ca

³ M.L.V. and R.M.P. made equal contributions to these studies, and the order of their names is arbitrary

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