Testosterone induced Ca2+ influx in bone marrow-derived macrophages via surface binding sites

The biological activity of testosterone is thought to occur predoininantly through binding to the androgen receptor (AR), a member of the nuclear receptor superfamily that functions as a ligand-activated transcription factor. Here, we found that testosterone could induce a rapid rise it? the intracellular free Ca2+ concentration ([Ca2+](i)) of Fura-2 loaded bone marrow-derived macrophages (BMMs), which was found to be predominantly due to the influx of extracellular Ca2+ through Ni2+-blockable Ca2+ channels in the plasma membrane. However, these effects of testosterone could not be associated with the classical intracellular AR in BMMs since AR was not delectable using different experimental techniques. Instead, it was found that testosterone could bind to the surface of BMMs by the use of an impermeable testosterone-BSA-FITC, and Ca2+ influx could also be induced by testosterone conjugated to BSA. Our data indicated a novel mode of direct action of testosterone on BMMs, which was not mediated through the classical AR response, but through the binding sites of testosterone on cell surfaces. (c) 2005 Prous Science. All rights resemed.