PARENT SESSION
TESTIS

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

(725) EXPRESSION OF THE SCAVENGER RECEPTOR CLASS B TYPE I (SR-BI) AND ITS ISOFORM SR-BII IN THE TISSUES AND IN THE TWO CELLULAR COMPARTMENTS OF THE TESTIS IN A SEASONAL BREEDER, THE MINK (Mustela vison).

Akpovi, Casimir¹, Vitale, María¹, Pelletier, R.-Marc¹, ¹ Dept. Pathology and Cell Biology, Montréal, QC, Canada

ABSTRACT- The Sertoli cells have been shown to possess the capacity to synthesise cholesterol from acetate in vitro. However, there is no evidence that these cells do so in vivo nor that they would be responsible for maintaining the total cholesterol concentration similar in the two cellular compartments of the testis namely, the seminiferous tubules and the interstitial tissue. Moreover, the fact that a blood-testis barrier prevents the free passage of substances including cholesterol and cells from the blood into the tubules suggests that the compound is transported into the seminiferous epithelium by a mechanism that allows to bypass the barrier. We measured the expression of the scavenger receptor class B type I (SR-BI) and its isoform SR-BII who we hypothesise are involved in this process. The mink, a seasonal breeder, was used as the animal model in this study. We detected a 82k Da SR-BI immunoreactive band in the testis, liver, pituitary, adrenal, lung, and traces in kidney, intestine and brain. Moreover, a 85 kDa SR-BII reactive band was detected in the same tissues but the intensity of the band was strongest in the testis, brain and kidney. In the mink testis, SR-BI and SR-BII expression was measured once a month throughout the annual seasonal reproductive cycle in seminiferous epithelium (STf) and interstitial tissue enriched fractions (ITf) respectively to assess the individual role of each receptor in each of the two compartments of the testis in relation to the spermatogenic activity. SR-BI expression significantly increased from October to February and decreased from March to June in the STf and ITf. Conversely, SR-BII expression significantly decreased from October to December but increased from January to February in the STf. In the ITf however, SR-BII expression significantly increased from November to June but decreased thereafter. The results support the concepts that SR-BI and SR-BII are involved in the intratesticular and intratubular cholesterol movement and transport and that the two receptors play distinct roles in these processes. Supported by NSERC.

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