EXPRESSION OF CLUSTERIN SULFATED GLYCOPROTEIN-2 UNDER CONDITIONS OF HEAT-STRESS IN RAT SERTOLI CELLS AND A MOUSE SERTOLI-CELL LINE

Clusterin is the major protein produced by rat Sertoli cells and is de posited onto sperm membranes; however, its function is unknown. In ord er to gain insight into the regulation of clusterin in Sertoli cells, the objective of the present study was to develop a model where the ex pression of clusterin could be affected in Sertoli cells in vitro. Rat Sertoli cells and mouse Sertoli cells (MSC1) were cultured under heat stress conditions (41 degrees C) for up to 48 hours. The mRNA for clu sterin in Sertoli cells was compared to that in human epitheliod cance r cells (A431) to determine if clusterin expression was regulated in a testis-specific manner. The mRNA for heat shock protein 70 (HSP70) wa s also examined as it is a known stress-regulated gene. Expression of HSP70 mRNA was increased in all three cell types by 4 hours after the start of heat stress. Clusterin mRNA was increased over that of contro ls by 4 hours in heat-stressed A431 cells but did not significantly in crease in MSC1 or Sertoli cells until 12 hours (P < 0.05). The inducti on of clusterin mRNA in MSC1 cells continued for at least 48 hours and required the sustained exposure of cells to the 41 degrees C temperat ure. The increase in the amount of clusterin mRNA was not due to an in crease in transcript half-life, as determined by the addition of actin omycin D to the media of control vs. heat-stressed MSC1 cells. From th e development of this in vitro model, we have seen that the timing of induction of clusterin by heat stress is Sertoli cell specific and is different than that of HSP70. This response in surviving cells during heat stress may be protective in that clusterin would bind to toxic co mpounds or solubilize cellular debris released by degenerating cells.