Expression, activity, and subcellular localization of testicular hormone-sensitive lipase during postnatal development in the guinea pig

The present work reports on testicular hormone-sensitive lipase (HSL), the biological significance of which has been documented in male fertility. The HSL protein levels and enzymatic activity were measured, respectively, by densitometry of immunoreactive bands in Western blots, performed with antib odies against recombinant rat HSL, and by spectrophotometry in seminiferous tubules (STf) and interstitial tissue (ITf) enriched fractions generated f rom neonatal, pubertal, and adult guinea pig testes. In addition, HSL was s tudied in subcellular fractions obtained from STf isolated from adult teste s and in epididymal spermatozoa (Spz). A 104-kDa HSL protein was detected i n STf and ITf, the expression and activity of which increased with testicul ar development. Three immunoreactive bands of 104, 110, and 120 kDa were de tected in the lysosomal subfraction, and two bands of 104 and 120 kDa were detected in Spz. The HSL activity was positively correlated with free (FC) and esterified (EC) cholesterol ratios in STf and IV, but not with triglyce ride (TG) levels, during testicular development. Immunolabeling localized H SL to elongated spermatids and Sertoli cells, where its distribution was st age-dependent, and within the cells lining the excurrent ducts of the testi s. The findings of the 104- and 120-kDa HSL immunoreactive bands and of HSL activity in Spz as well, as the detection of the 104-, 110-, and 120-kDa i mmunoreactive bands in lysosomes, suggest that part of HSL may originate fr om germ cells and be imported in Sertoli cells. The HSL protein levels and enzymatic activity in ITf and STf were positively correlated with serum tes tosterone levels during development. To the best of our knowledge, this stu dy is the first to contribute insights regarding the impact of HSL on FC:EC cholesterol ratios and TG levels in the interstitial tissue and tubules in relation to serum testosterone levels during postnatal development, and re garding the immunolocalization of the enzyme in regions of the male gamete consistent with spermatozoa-oocyte interaction.