Blood plasma proteins modulate the broncholytic effects of a muscarinic receptor antagonist.

Blood plasma proteins modulated the effects of muscarinic receptor antagonist methacin. Administration of methacin in combination with albumin or C-reactive protein (but not with IgG) abolished the broncholytic effect of methacin. It was probably associated with allosteric antagonism to M2, cholinergic receptors on non-nervous cells, which increased antibody production and mediator response. The concentration of serotonin in mesenteric lymph nodes was high during shock.