Effects of carp pituitary fractions on vitellogenesis, ovarian maintenance, and ovulation in hypophysectomized catfish, Heteropneustes fossilis (Bloch).

Abstract

SUMMARY Carp pituitary extracts obtained from the puntius carp, Puntius gonio-notus, the grass carp, Ctenopharyngodon idellus, and the big head carp, Aristichthys nobilis, were subjected to gel filtration on Sephadex G-100. The water-soluble proteins in the pituitary extracts resolved into three distinct components, referred to as fractions I, II and III. They were tested for their gonadotrophic activity in the female catfish, Heteropneustes fossilis, by evaluating ovarian maintenance and ovulation in hypophysectomized gravid specimens during the spawning season (July—August), and the induction of oogenesis and vitellogenesis in the regressed ovaries of hypophysectomized specimens during the preparatory period (February). Daily treatment with the puntius carp pituitary fraction II (100 or 300 μg) reinitiated and restored oogenesis and vitellogenesis. The grass carp pituitary fraction II (300 μg) induced vitellogenesis but its potency was much less than that of the puntius carp pituitary fraction II. The big head carp pituitary fraction II was ineffective. Daily treatment with the puntius carp pituitary fraction II (1 or 5 μg) maintained the yolky oocytes in the gravid ovaries and prevented atresia. Ovulation and spawning were induced in hypophysectomized gravid catfish by a single dose of the puntius carp pituitary fraction II (100 or 150 μg). The first and third fractions from the three species of carps were ineffective. Thus, all the reproductive processes in the hypophysectomized female catfish were initiated and/or maintained solely by the puntius carp pituitary fraction II.