Catecholamine Clearance from Alveolar Spaces of Rat and Human Lungs

Abstract

Background: Although aerosolized β-adrenergic agonists have been used as a therapy for the resolution of pulmonary edema, the mechanisms of catecholamine clearance from the alveolar spaces of the lung are not well known. Objective: To determine whether catecholamine clearance from the alveolar spaces is correlated with the fluid transport capacity of the lung. Methods: Albumin solution containing epinephrine (10^–7M) or norepinephrine (10^–7M) was instilled into the alveolar spaces of isolated rat and human lungs. Alveolar fluid clearance rate was estimated by the progressive increase in the albumin concentration over 1 h. Catecholamine clearance rate was estimated by the changes in catecholamine concentration and alveolar fluid volume over 1 h. Results: The norepinephrine clearance rate was faster than the epinephrine clearance rate in the rat and human lungs. In the rat lungs, amiloride (a sodium channel blocker) caused a greater decrease in alveolar fluid clearance and epinephrine clearance rate than propranolol (a nonselective β-adrenergic antagonist). Although propranolol and phentolamine (an α-adrenergic antagonist), and 5-(N-ethyl-N-isoprophyl)amiloride (a Na⁺/H⁺ antiport blocker) changed neither the alveolar fluid clearance nor the norepinephrine clearance rate, amiloride and benzamil (a sodium channel blocker) decreased both clearance rates. As in the rat lungs, amiloride decreased alveolar fluid and norepinephrine clearance rates in the human lungs. Conclusion: These results indicate that the catecholamine clearance rate from the alveolar spaces is correlated with alveolar fluid clearance in rat and human lungs.

Ketamine Inhibits Lung Fluid Clearance through Reducing Alveolar Sodium Transport

“…In this setup, the rate of ex vivo AFC was significantly reduced in human lobes intratracheally administrated ketamine. Addition of amiloride to the instillate decreased AFC by about 50%, which is in accordance with previous studies [17, 18, 22, 24]. Previous studies showed that S-ketamine via iv at clinically relevant bolus concentrations does not affect AFC in rats [25], the difference might result from the many divergent properties of ENaC between different species.…”

“…Preoperative pulmonary function tests were normal in all patients (see Table 1). The surgical procedure and lung segment chosen were done as described previously [17, 18]. Briefly, immediately after removal of the lung, we occluded the segmental bronchus with a 10-Fr.…”

Adrenergic Influence on the Permeability of Sheep Diaphragmatic Parietal Pleura

“…This additive effect indicates that adrenergic stimulation acts by an amiloride-independent mechanism. In a previous in vivo study in humans and rats amiloride was shown to change adrenaline alveolar clearance; however, this effect does not apply to our in vitro experiments [11] . In previous animal studies regarding the sodium transport in rabbit experimental hydrothoraces, Zocchi et al [12] also reported that the ␤ -adrenergic influence was amiloride insensitive.…”

8-(4-Chlorophenylthio)-Guanosine-3′,5′-Cyclic Monophosphate-Na Stimulates Human Alveolar Fluid Clearance by Releasing External Na+ Self-Inhibition of Epithelial Na+ Channels

“…Human lung segments were prepared and AFC measurements were done as described previously (27,28). Briefly, the segmental bronchus was occluded by a 10-Fr.…”