Are so many adrenergic receptor subtypes really present in domestic animal tissues? A pharmacological perspective

Bovine ovarian and myometrial cell membranes express higher concentrations of β2-ARs than the β1 subtype, whereas as far as α-ARs are concerned, a single class of α1-ARs and two distinct classes of α2-AR binding sites have been discriminated. Interestingly, it has been observed that the activation of the sympathetic system could play an important role in the pathogenesis of bovine ovarian cysts as suggested by the modifications in β-AR levels in the hypophysis and ovary of cows affected by ovarian cysts. In this species, the phenomenon of down-regulation has been well studied in different organs of veal calves treated with clenbuterol as a “partitioning agent”. Since differences exist in AR distribution among species, data obtained in laboratory animals or in human beings cannot be extrapolated to domestic animals and further investigation on AR subtypes in domestic animal tissues is necessary.