5. Temperature Dependency of Gonadotropin Binding Reaction to Its Receptor in Poikilothermic and Homeothermic Vertebrates(Lectures presented at the Seminar of Japanese Society for Research of Freezing and Drying : "Low Temperature and Living Organisms")

Abstract

Effects of temperature on the kinetic and equilibrium parameters of the binding reaction of a gonadotropic hormone (follicle stimulating hormone, FSH) to its receptor in both homeothermic and poikilothermic vertebrates were studied, since we found that FSH could bind to its receptors at low temperatures in poikilotherms but not in homeotherms. The association rate constant in poikilotherms was significantly less affected by temperature than in homeotherms. The equilibrium constant of association was high at around 37℃ and decreased by lowering the temperature. That of amphibians was maximum between 15 and 25℃ and decreased as a whole at higher temperature. The affinity in a turtle did not vary significantly in the temperature range between 0 and 40℃. These optimal temperatures coincided well with the temperatures at which gonadotropin acts on the gonad in each species under the natural condition.