Constancy of arterial blood pH during CO-induced hypoxia in the rainbow trout

Abstract

Rainbow trout were exposed to water equilibrated with 5% CO and 21% O2 for 30 min. During the exposure dorsal aortic blood pH remained stable at about 8.1 while breathing rate and pressure and heart rate and blood pressure increased. The bradycardia generally associated with environmental hypoxia was absent. It is suggested that the observed circulatory and respiratory responses were not due to acid–base related factors but rather to the stimulation of oxygen receptors. The findings suggest the presence of at least two loci of oxygen-sensitive respiratory control mechanisms in trout.