REGULATION OF ALPHA(2)-MACROGLOBULIN EXPRESSION IN RAT SERTOLI CELLS AND HEPATOCYTES BY GERM-CELLS IN-VITRO

Germ cells isolated from rat testes by trypsinization have been shown to yield unwanted artifacts in biological assays, since conditioned me dia derived from these germ cells (germ cell-conditioned media [GCCM]) can modulate Sertoli cell secretory function because of the presence of residual trypsin. To determine whether germ cells themselves can mo dulate Sertoli cell function, we isolated germ cells from tubules by a mechanical procedure and assessed the effect of these cells on Sertol i cell alpha(2)-macroglobulin (alpha(2)-MG) steady-state mRNA level, l it was found that germ cells indeed could stimulate Sertoli cell alpha (2)-MG expression. This effect is probably mediated by a soluble facto r(s) released from germ cells, since GCCM fractionated by HPLC contain ed multiple fractions that can stimulate Sertoli cell alpha(2)-MG expr ession dose-dependently, These results illustrate that germ cells play a role in regulating testicular alpha(2)-MG expression. Since Sertoli cells synthesize and secrete many of the serum proteins behind the bl ood-testis barrier that are also produced by hepatocytes, we sought to ascertain whether germ cells can affect hepatic alpha(2)-MC expressio n. When germ cells were cocultured with hepatocytes isolated from adul t rats, the hepatocyte alpha(2)-MG steady-state mRNA level was shown t o be stimulated by germ cells dose-dependently. Using different pools of fractions derived from GCCM after their fractionation by a preparat ive anion-exchange HPLC column, GCCM was found to contain a factor(s) that stimulated hepatocyte alpha(2)-MG expression dose-dependently. Mo re importantly, the fractions that stimulated hepatocyte alpha(2)-MG e xpression had a retention time different from that of the factor(s) th at affected Sertoli cell alpha(2)-MG expression. These data illustrate that germ cells secrete multiple biological factors capable of regula ting alpha(2)-MC expression in the testis and the liver. In summary, t his study reveals a possible physiological link between the testis and the liver in that germ cells may release a factor(s) capable of modul ating alpha(2)-MC expression in both organs.