Testosterone metabolism in neuroendocrine and peripheral tissues of male Japanese quail during photoinduced sexual maturation

Abstract

Abstract Changes in testosterone metabolism in neuroendocrine tissues and the cloacal gland of the Japanese quail were studied by an “in vitro” approach in immature birds raised in short day lengths and in maturing birds after 2, 4, 6, 8, 12, 20 days of photostimulation (16 h light, 8h darkness). Androstenedione, 5β-DHT, 5β-3α-diol and 5α-DHT were identified as the main metabolites of testosterone in the pituitary and in the cloacal gland. No 5α-DHT was found in incubates from the hypothalamus and hyperstriatum. In the pituitary gland, the hypothalamic and the hyperstriatal tissue conversion of testosterone into androstenedione was low in short day birds. After photostimulation conversion into androstenedione increased progressively in all tissues studied. Conversion to 5β-reduced metabolites was highest in short days and decreased progressively as the birds matured. Conversion to 5α-DHT was low in short day birds and increased significantly after 12 days of photostimulation. In the cloacal gland conversion into androstenedione was also low in short day birds and increased progressively during photostimulation while conversion into 5β-reduced metabolites decreased progressively during the same period. A slight increase in the conversion to 5α-DHT occurred in the cloacal gland after 12 and 20 long days. These data suggest that in the quail, as in the cockerel, the decrease of 5β-reductase activity in the neuroendocrine tissues may be involved in the initiation of puberty.