Characterization of bovine neutrophil β 2 ‐adrenergic receptor function

LaBranche, T. P., Ehrich, M. F., Eyre, P. Characterization of bovine neutrophil β 2 ‐adrenergic receptor function. J. vet. Pharmacol. Therap. doi: 10.1111/j.1365‐2885.2009.01143.x. This study compares bovine leukocyte β‐adrenergic receptor densities to that of the rat, demonstrates for the first time a functional β 2 ‐adrenergic receptor signaling pathway in steer neutrophils, and investigates the effect of an inflammatory stimulus on that signaling pathway. The β 1 ‐/β 2 ‐adrenergic antagonist [3H] CGP‐12177 demonstrated that rat lymphocyte specific binding‐site density was highest, followed by steer and dairy cow lymphocytes, and lastly steer and dairy cow neutrophils. The β 2 ‐adrenergic agonist terbutaline stimulated steer neutrophil adenosine 3,5‐cyclic monophosphate (cAMP) production, an effect increased by inclusion of ≥1 × 10 −8  m phorbol 12‐myristate 13‐acetate (PMA), an activator of protein kinase C. Both terbutaline and the nonselective phosphodiesterase inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX) independently decreased steer neutrophil superoxide anion production in a concentration‐dependent manner, with 1 × 10 −4  m IBMX enhancing both the potency and efficacy of the terbutaline effect (up to 74% reduction in superoxide anion production). Superoxide anion production was also reduced by the synthetic cAMP analog 8‐bromo‐cAMP, which increased the potency of the IBMX effect on superoxide anion production. Taken together, these data demonstrate the presence of a β 2 ‐adrenergic receptor signaling pathway in bovine neutrophils much like that described in other animal species, as well as the potential for an inflammatory stimulus to alter its function.