An isolated perfused dog lung preparation for the study of cyclic GMP metabolism: effects of sodium nitroprusside and oxygen.

The intact, isolated perfused dog lung was evaluated as a model for studies directed at defining the role of oxidative modulation of lung cyclic GMP metabolism in pulmonary function. Sodium nitroprusside added to the perfusion blood increased the cyclic GMP content of lung over 4-fold in a dose-dependent manner. Although sodium nitroprusside administration caused changes in lung vascular resistance, these occurred independently of the changes in cyclic GMP. Ventilation of lungs with a high oxygen gas mixture containing 95% O2. 5% CO2 acutely increased the cyclic GMP content of lungs after 15 min from 1.3 +/- 0.06 (mean +/- SE) to 3.4 +/- 0.12 pmol cyclic GMP/mg protein. Cyclic GMP levels returned toward control during continued ventilation with the high oxygen concentration. The oxygen-induced elevation of lung cyclic GMP content was not accompanied by changes in lung vascular resistance. The results indicate that the isolated perfused lung may be useful in studies of cyclic GMP, tissue oxidation and pulmonary function.