Humic acid induced growth retardation in a Sertoli cell line, TM4

Humic acid (HA) is a fluorescent deep brown organic, polymeric compound com posed of phenolic acid. Intraperitoneal injection of HA in rats induced tes ticular morphological changes including degeneration of the seminiferous tu bule, reduction in the number of Sertoli cells and spermatogonia, and a los s of spermatids. It was suggested that Sertoli cells may be involved in the progression of testicular atrophy. In this study, we used a mouse Sertoli cell Line, TM4, to investigate the effect of HA on Sertoli cells and the me chanism of the testicular atrophy induced by HA. We found that the cell gro wth of TM4 cells were reduced in 1 to 4 days of HA exposure. FACScan analys is of the DNA content of HA-treated TM4 cells revealed that there was no su b-G, peak, indicating that the TM4 cells did not commit to the programmed c ell death. However, a large proportion of TM4 cells were arrested at the Gl phase. The percentage of TM4 cells at the Gl phase increased from 36% to 8 4% after HA treatment for 4 days. Western blot assay of HA-treated TM4 cell s showed that the expression of cyclin D-1 protein decreased while the expr ession of p27(kip1)protein increased. These results suggest that HA-induced testicular atrophy is linked in part to an inhibitory effect on the growth of Sertoli cells. This model may be useful in investigation of environment al agents inducing testicular atrophy. (C) 2001 Elsevier Science Inc. All r ights reserved.