Pulmonary vascular β-adrenoreceptor activity in conscious dogs after left lung autotransplantation

Our objective was to determine whether chronic denervation associated with left lung auto-transplantation (LLA) results in an alteration in sympathetic β-adrenoreceptor regulation of the pulmonary circulation in conscious dogs. Continuous left pulmonary vascular pressure-flow (LPQ̇) plots were generated in conscious dogs 2-4 wk post-LLA and in sham-operated control conscious dogs. We tested the hypothesis that endogenous sympathetic β-adrenoreceptor activation via circulating catecholamines acted to attenuate the chronic increase in pulmonary vascular resistance post-LLA. Administration of the sympathetic β-adrenoreceptor antagonist propranolol had no significant effect on the LPQ̇ relationship post-LLA. We also tested the hypothesis that pulmonary vascular reactivity to sympathetic β-adrenoreceptor activation would be increased post-LLA. The thromboxane analogue U-46619 was used to acutely preconstrict (P < 0.01) the pulmonary circulation in control dogs; this preconstriction shifted the LPQ̇ relationship to the same position measured post-LLA. Under these conditions, cumulative doses of the β- adrenoreceptor agonist isoproterenol caused pulmonary vasodilation (P < 0.01) in the control group but had no effect post-LLA. However, after acute preconstriction with U-46619, the pulmonary vasodilator response (P < 0.01) to isoproterenol post-LLA was not significantly different from that in the control group. These differential responses to isoproterenol with and without acute preconstriction indicate that a significant component of the chronic increase in pulmonary vascular resistance post-LLA is mediated by passive nonvasoactive mechanisms. Moreover, sympathetic β-adrenoreceptor reactivity of the pulmonary circulation is not enhanced by chronic denervation resulting from the LLA procedure.