Specificity of a new lipid mediator produced by testicular and peritoneal macrophages on steroidogenesis

Macrophage-derived factor (MDF) is a lipophilic factor produced by rat test icular and peritoneal macrophages that maximally stimulates testosterone pr oduction by rat Leydig cells through a steroidogenic acute regulatory prote in independent mechanism. The purpose of the present study was to determine whether MDF is also produced by human macrophages, and/or if it acts on hu man steroidogenic cells. We also studied the tissue-specific functions of M DF by determining if it also acts on steroidogenic cells of the ovary and a drenal glands and, if so, does it require new protein synthesis. It was fou nd that MDF was produced by human peritoneal macrophages, and was capable o f stimulating human steroidogenic cells. In terms of tissue specificity, it was found that primary cultures of rat adrenocortical cells respond to MDF with increased secretion of aldosterone and corticosterone, as did rat gra nulosa cells by producing progesterone. MDF acted in the presence of cycloh eximide, indicating that it does not require new protein synthesis. These r esults indicate that MDF may have significant therapeutic potential and pro vide a basis for future studies concerning its physiological role in humans . These results further suggest that MDF is not only involved in paracrine regulation of Leydig cells, but also has the potential for the local regula tion of steroidogenesis in both granulosa and adrenal cortical cells.