Catecholamines can induce pulmonary remodeling in rats

Previously, we found that catecholamine (CA) infusion in rats induced pulmonary injury with edema and inflammation resembling acute lung injury in humans. Here, we examined effects of norepinephrine (NE) and of selective α- and β-adrenergic agonists on the remodeling of pulmonary extracellular matrix.

Eighty rats were infused over 8-72 h with NE, phenylephrine (PE), isoproterenol (ISO) or NaCl solution. We investigated mRNA expression of collagen, matrix metalloproteinase (MMP)-2, its tissue inhibitor (TIMP-2) and transforming growth factor (TGF)-β isoforms in lung tissue. Additionally, lung histology, hemodynamic function and cardiac hypertrophy were evaluated.

After 72 h of infusion, lung histology showed beginning fibrosis and vascular hypertrophy. Collagen type I, MMP-2 and TIMP-2 mRNA expression were significantly elevated. All these effects were most pronounced with NE while PE and ISO induced weaker responses. TGF-β mRNA expression was also elevated after 72 h, predominantly after PE infusion. Cardiac hypertrophy was most pronounced after ISO infusion.

CA infusion over 72 h may induce pulmonary remodeling. Mainly α-adrenergic but also β-adrenergic mechanisms contribute to these processes. In contrast, cardiac hypertrophy is predominantly mediated by β-adrenergic stimulation and hence, is considered to be a direct adrenergic effect rather than a consequence of pulmonary fibrosis.