Sympathetic neuroeffector transmission to pulmonary vascular smooth muscle in porcine superior mesenteric arterial occlusion (SMAO) shock.

Splanchnic arterial occlusion shock results in pulmonary endothelial damage and depression of porcine intralobar pulmonary artery and vein contractility. This study evaluates the functional integrity of the adrenergic nerves innervating intralobar pulmonary arteries and veins and the changes in neurotransmission following 1) superior mesenteric artery occlusion (SMAO) shock in swine; 2) sequential inhibition of prostacyclin, thromboxane, and prostaglandin synthesis; and 3) mechanical stripping of the endothelium. Rings of porcine intralobar pulmonary arteries and veins were obtained from sham and SMAO shocked swine. They were suspended in muscle baths and stimulated transmurally at 1-32 Hz, 2 msec duration, 2 msec delay at 7.5-10V. Some experiments were performed on rings of intralobular pulmonary arteries and veins in which the endothelium was stripped with a razor blade. Appropriate inverted-reverted controls were used to account for any deleterious effects of the preparatory techniques involved in stripping. Intralobar pulmonary arteries and veins from sham swine contracted in response to 1 Hz, with maximum responses at 32 Hz. The responses to nerve stimulation were enhanced by cocaine and inhibited by phentolamine, an alpha-receptor antagonist. Inhibition of endothelial prostacyclin synthesis, as well as endothelial stripping, diminished by 30-40% the responses to nerve stimulation. The responses to nerve stimulation were depressed in both intralobar pulmonary arteries and veins in SMAO shocked swine. The data demonstrate physiologic regulation of neural control in porcine pulmonary blood vessels. Furthermore, the data suggest that prostaglandin, the vascular endothelium, and shock, may modify this process.