The Effect of Methallibure (ICI Compound 33, 828) on Folliculogenesis and Steroidogenic Potential of Developing Ovary in the Lizard, Calotes versicolor (Daud.)

Abstract

In vertebrates, it is well established that gonadotropins are crucial for vertebrate ovarian development and its endocrine functions. The current investigation envisages determining how methallibure affects the histoanatomical structure and steroidogenic capacity of the developing ovary of 10-day-old female hatchlings of Calotes versicolor. The eggs were collected from gravid females during the breeding season and incubated at a female-producing temperature of 31.5±0.5 oC till hatching. Hatchlings were fed with live termites. Intraperitoneal injections of 6μg of methallibure in 0.05ml of 0.7% saline were injected into 10-day-old female hatchlings on alternate days for 21 days. The appropriate saline-treated hatchlings served as control. The results reveal that methallibure significantly reduces the number of oocytes (P<0.02) and primordial follicles, decreases their diameter, and increases the number of previtellogenic atretic follicles (P<0.001) with concomitant suppression of the progression of ovarian development when compared with that of baseline control. Three types of atretic follicles were noticed. The histoenzymatic activity of Δ5-3β-hydroxysteroid dehydrogenase in the ooplasm of the follicle and the stromal region showed a decreased intensity. The downregulation of steroidogenesis is probably due to the deprived secretion of gonadal steroids which disturbs the negative feedback mechanism because of the action of the drug at the hypothalamic-hypophyseal-ovarian axis. The present study unveils that methallibure acts as an antigonadotrophic drug altering the synthesis/secretion of gonadotrophin by hypophysis. It is inferred that methallibure induces an anti-gonadotropic effect in the newly hatched hatchlings probably by quenching the pituitary gonadotropins.