The role of imidazole ionization in the control of breathing

Interacting effects of pH and temperature on ventilation in turtles and alligators have suggested that pH is monitored in terms of imidazole ionization, but the view that this is true in alligators and ectotherms generally has been attacked. Published evidence re-interpreted here indicates that this "alphastat control" could indeed operate in turtles, alligators, chickens (i.e. intrapulmonary chemoreceptors) and perhaps cats. Nevertheless, studies on temperature effects cannot distinguish with certainty between imidazole and some amino groups in this context.