Steroid levels in preovulatory and gravid lizards ( Uromastix hardwicki)

Abstract

Progesterone, testosterone, and estradiol-17β were measured by radioimmunoassay in the plasma and ovarian tissues of preovulatory and gravid spiny-tailed lizards ( Uromastix hardwicki). Plasma titers of all three steroids were significantly higher in females carrying the oviductal eggs as compared to the values obtained in the preovulatory animals. Progesterone content of the corpora lutea present in the ovaries of gravid females was several times higher than the concentration of this hormone in the preovulatory follicular tissue. Testosterone and estradiol concentrations were also significantly higher in the luteal than in the follicular tissues. These data suggest that the rise in plasma levels of steroids during gravidity is mainly due to the steroidogenic activity of the corpus luteum and that the functions generally attributed to the reptilian luteal tissue may be mediated not only by progestins alone but also by other steroids synthesized by the corpus luteum in this reproductive phase.