The effect of temperature acclimation on myocardial β-adrenoceptor density and ligand binding affinity in African catfish (Claris gariepinus)

This study assessed the effects of temperature acclimation on myocardial β-adrenoceptor density (Bmax) and binding affinity (Kd) in African catfish (Claris gariepinus) acclimated to 15, 22 and 32 °C. Bmax values were not significantly different (P > 0.05) among the three acclimation groups. Conversely, the Kd value of the 32 °C acclimation group (Kd = 0.88) was significantly higher (P = 0.002) than both the 15 °C (Kd = 0.48) and 22 °C (Kd = 0.46) acclimation groups. In addition, Kd of rainbow trout (Oncorhynchus mykiss) was significantly lower (P < 0.001) and Bmax significantly higher (P < 0.05) than that of African catfish at all three acclimation temperatures. These results contrast with those reported previously for temperate species, in which Bmax is inversely related to acclimation temperature, and counter a previous suggestion that Bmax is higher in tropical versus temperate species.