The role of LH-RH in induction of spawning in grass carp (Ctenopharyngodon idellus). I. Cytological and histochemical studies of the pituitary and of the ovary.

Histochemical studies indicate that in teleost, just like the case in mammalian species, the functional changes of the pituitary and the ovary are directly and indirectly under the control of the hypothalamic releasing hormone. The medium lobe of the grass carp's pituitary has only one type of gonadotroph which contains two kinds of granules differing in size and staining reaction. The gonadotrophs show extensive activity of hormone synthesis and release following the LH-RH treatment. This is evidenced by the progressing decrease in number of the small granules, increase in number and size of the huge heterogenous granules and the appearance of cytoplasmic vacuolation. The small granules are likely to be the LH secreting granules and the huge granules, the FSH secreting granules. Owing to the rapid elevation of pituitary LH, the ovary is activated. This is demonstrated by the increased activities of G-6-Pase, AKP, 3 beta-0H-SDH, and ACP in the follicular cells of the ovary after hormonal treatment. The result suggest that the steroid hormone plays an important role in the regulation of the gonadotropin action.