Testosterone-dependent transformation of nephronic tubule cells into serous and mucous gland cells in stickleback kidneys in vivo and in vitro

Abstract

When male sticklebacks come into breeding condition, the cells of the second proximal segments and collecting tubules of the nephrons are transformed into cells producing secretions used for nest building. This investigation is aimed at determining whether this transformation of renal tubule cells is induced directly by androgens. To this end, renal tissue is cultured with androgen supplement, either methyltestosterone or 11-ketotestosterone. The results are compared with the effects of methyltestosterone on the tubule cells in castrated males. In the nephronic tubules of methyltestosterone-treated fish, the basal labyrinth—and thus most of the ion reabsorbing capacity of the tubules—disappears within 4 days, probably as a result of autophagous digestion. During this period the cells become considerably enlarged and an extensive granular endoplasmic reticulum develops. The Golgi apparatus proliferates and starts to form secretory granules. In renal tissue cultured for 10 days with methyltestosterone, secretory granules are observed in the second proximal tubule cells, but no secretory activity can be detected in the collecting tubules. After 5 days in cultures supplemented with 11-ketotestosterone, however, signs of secretory activity are apparent already in the second proximal tubules, and to a lesser extent, in the collecting tubules. After 10 days of incubation with 11-ketotestosterone, glandular transformation is almost completed. The results provide strong evidence that the transformation of nephronic tubule cells into mucus-secreting cells in sexually mature sticklebacks is due to a direct effect of androgen. It can be concluded then that, at least in vitro, 11-ketotestosterone may be considered more androgenic than methyltestosterone.