Effects of clodronate-containing liposomes on testicular macrophages and Leydig cells in vitro.

We undertook the present studies to determine if clodronate-containing liposomes have direct effects on Leydig cells. Macrophages and Leydig cells were isolated and maintained separately in culture. Following treatment with clodronate-containing liposomes, macrophages were killed in a dose-response fashion over a range of 5-200 microliters liposomes. By comparison, a 500 microliters dose was required to kill Leydig cells, but this was not dependent upon clodronate since liposomes containing buffer elicited an identical response. The concentration of testosterone in medium from Leydig cells treated with clodronate-containing liposomes was significantly reduced compared with untreated cells. However, we subsequently found that liposomes can adsorb testosterone. Therefore, testosterone production was determined at various times following removal of liposomes from Leydig cells, thereby circumventing this complication. It was found that testosterone production was not altered by liposomes under these conditions. Finally, free clodronate had no effect on testosterone production, even at doses representing the amount present within the 500 microliters dose of liposomes. In summary, clodronate-containing liposomes killed testicular macrophages at a far smaller dose than required to kill Leydig cells. Most importantly, neither liposomes no free clodronate had a direct effect on testosterone production. Thus, clodronate-containing liposomes represent a valuable tool to study Leydig cell-macrophage interactions.