PARENT SESSION
TESTIS

Wednesday, August 4, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(729) CD 36 INFLUENCES DIFFERENTLY THE EXPRESSION OF DISTINCT ISOFORMS OF THE HORMONE-SENSITIVE LIPASE IN EACH COMPARTMENT OF THE TESTIS.

Chen, Li¹, Akpovi, Casimir¹, Ong, Huy², Vitale, María¹, Pelletier, R.-Marc¹, ¹ Dept. Pathology and Cell Biology, Montréal, Québec, Canada² Faculty of Pharmacy, Université de Montréal, Montréal, Québec, Canada

ABSTRACT- In the testis, cholesterol is present in similar concentration in the seminiferous tubules and the interstitial tissue. Because cholesterol is an essential component of all cellular membranes and a precursor of steroid hormones, in the testis, the compound is crucial for the development of germ cells, the fertility of spermatozoa as well as for the maintenance of adequate testosterone levels. Here, we investigate the role of CD36, a receptor for oxidized low density lipoproteins (ox LDL), high density lipoproteins (HDL) in the maintenance of the homeostasis of cholesterol levels in the two cellular compartments of the testis: the tubules and the interstitial tissue. To distinguish CD36 expression in the tubules from that in the interstitial tissue, we measured by Western blot analyses the CD36 expression separately in normal seminiferous tubule enriched (STf) and in interstitial tissue enriched fractions (ITf). We detected a 88- and a 96-kDa CD36 immunoreactive bands, the intensity of the former band was more than twice that of the latter. In addition, the levels of the two immunoreactive bands were significantly higher in the ITf than in the STf. To assess whether CD36 expression does have an effect on key factors involved in the metabolism of cholesterol in the testis, we measured the hormone-sensitive lipase (HSL) expression in the STf and ITf of wild type (wt) and CD36 knock out (-/-) mice. In the wt mice, the expression of the 120-, the 108- and the 104-kDa HSL isoforms was normally 30% higher in the STf than in the ITf and the expression of the 84-90-kDa HSL isoform was similar in STf and ITf. However, in the CD36 -/- mice, the expression of the 120-, 108- and 104-kDa HSL isoforms was increased by 30% in the ITf while the expression of these three bands and that of the 84-90-kDa remained unchanged in the STf. The results show that blocking the gene expression of CD36 modifies the expression of the 120-, 108- and 104-kDa HSL isoforms only in the interstitial tissue of the testis. It is hypothesized that this modification reflects in part the effect of CD36 on the transport of cholesterol to the Leydig cells. Supported by NSERC.

KEY WORDS: male reproductive system, lipids, testis, cholesterol