Adrenergic receptor density in brown adipose tissue of active and hibernating hamsters and ground squirrels

The ligand-binding characteristics (Bmax and KD) of α1- and  β1/β2-adrenoceptors were investigated in membranes prepared from brown adipose tissue (BAT) of warm-acclimated, cold-acclimated, hibernating and arousing ground squirrels (Spermophillus undulatus) and hamsters (Mesocricetus auratus) by specific binding of [3H]prazosin and [3H]CGP-12177, respectively. The physiological state did not change the affinity for the adrenoceptors in the BAT of ground squirrels and hamsters. There was a significant decrease in α1-receptor density in arousing ground squirrels and a significant decrease in β1/β2 density in hibernating ground squirrels. The level of α1-receptors was in all conditions higher than that of β1/β2 receptors. The results indicate a possible change in balance of adrenoceptor density in the processes of cold acclimation, hibernation and arousal. The balance between the various adrenoceptor subtypes may be important for the final effect of catecholamines in BAT in different physiological states.