Avian gonadotropin receptors: a comparative view.

Avian testicular receptors for gonadotropins show a species-specificity similar to mammalian receptors for the binding affinity to gonadotropins of various origins. In the affinity-capacity relationships, avian FSH receptors are classified in the same group with chelonians, that is, they exhibit relatively low affinity and high capacity. FSH receptors of the Japanese quail resemble the rat receptor with respect to the temperature-dependence of affinity in the low-temperature range, but also resemble reptilian or amphibian receptors with respect to binding affinities in the middle- to high-temperature range. We conclude that avian gonadotropin receptors have some characteristics of homeothermic vertebrates, but still retain characteristics of poikilothermic groups.