Mammalian and chicken I forms of gonadotropin-releasing hormone in the gonads of a protochordate, Ciona intestinalis

Two forms of gonadotropin-releasing hormone (GnRH) were isolated from the g onads of the tunicate, Ciona intestinalis. The primary structure of the pur ified peptides was determined by MS and chemical sequence analysis. Both Gn RH forms have blocked NH2 and COOH termini, and their primary structures ar e identical to mammalian (mGnRH) and chicken I (cGnRH-I) forms reported pre viously in vertebrates. A total of 1.2 mg of purified cGnRH-I and 0.98 mg o f mGnRH was obtained from 100 g of Ciona gonads. The physiological effects of native GnRHs included the induction of synthesis and secretion of sex st eroids from ciona gonads and the secretion of luteinizing hormone from rat pituitary. These results suggest that the primary structure and functional roles of mGnRH and cGnRH-I have been highly conserved throughout evolution of chordates.