Evolution and Adaptation of Gonadotropin Receptors

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We used radioiodinated homologous gonadotropins of the mammal, bird, amphibia and fish, and studied their specific bendings to the gonad of the homologous and heterologous species. From results of these studies, it was concluded that the fish has a single type gonadotropin and corresponding single type gonadotropin receptors, the amphibia or at least the anuran amphibia has two type gonadoftropins of FSH and LH but single type gonadotropin or FSH/LH receptors, and the bird has two type gonadotropins of FSH and LH and corresponding two type receptors for FSH and LH, respectively. We also showed some evidences showing that fish has multiple type qonadotropins but they are not homologous nor analogous to FSH and LH.We postulated that the differentiation of gonadotropin molecules to FSH and LH took place in the ancestral amphibian but the differentation of the corresponding two type receptors took place later in the ancestral reptilian during the course of the vertebrate evolution. Further studies in the retilia are needed. We also found that the liver of amphibians has specific receptors for gonadotropins of the homologous species or group and these recetors are coupled withe the mmbrane-bound adenylate cyclase. The physiological role of the gonadotropin receptors in the amphibian liver must be clarified.