The effects of type 1 diabetes mellitus and of tobacco smoke on dissipation of catecholamines in pulmonary endothelial cells--a non-neuronal site of uptake1.

The effects of Type 1 diabetes mellitus and of exposure to mainstream cigarette smoke on noradrenaline (NA) uptake and its subsequent metabolism by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in the perfused lungs of rats were examined. In diabetic (streptozotocin-treated) rats, there was an increase in the metabolic clearance of NA in the lungs, and this appeared to be due to the observed increase in NA uptake. During acute exposure of rat lungs to cigarette smoke, there was again an increase in the metabolic clearance of NA, and this was not due to any increase in the activity of either COMT or MAO, but we have not yet investigated whether it is due to an increase in NA uptake. After prolonged exposure of rats to cigarette smoke (daily for 3 months), NA uptake in the lungs was increased, but there was no change in the activity of either COMT or MAO. The results suggest that increased pulmonary clearance may reduce the elevated plasma catecholamine levels that have been described both in patients with Type 1 diabetes mellitus and in cigarette smokers.