Sexual dimorphism in phagocytic activity of wall lizard's splenic macrophages and its control by sex steroids.

The splenic macrophages of wall lizards exhibited marked sex-related difference in their phagocytic activity. The percentage phagocytosis and phagocytic index in females was considerably higher than that of males. Gonadectomy resulted in significant increase in percentage phagocytosis and phagocytic index in both male as well as female lizards, suggesting that gonadal hormones inhibit macrophage phagocytosis. This was further confirmed by dose and time-related in vivo and in vitro experiments in which DHT suppressed phagocytosis which increased with dose or duration of treatment, while E(2) either suppressed or had no effect on phagocytosis, depending on dose and duration of treatment. Exposure of macrophages to steroid receptor antagonists, cyproterone acetate (CPA), or tamoxifen citrate (Tam) prior to treatment with their respective sex steroids markedly reduced the DHT- or E(2)-modulated suppression of macrophage phagocytosis. It is concluded that the sex steroids modulate splenic macrophage phagocytosis via receptor-mediated systems. Copyright 1999 Academic Press.