Melatonin administration acutely decreases the diffusing capacity of carbon monoxide in human lungs

Most physiological measurements of the pulmonary diffusing capacity use carbon monoxide (CO) as a tracer gas. Similar to CO, melatonin binds the hemoglobin in the blood.

The present study was designed to assess the effect of exogenous melatonin administration on pulmonary functions including diffusing capacity for carbon monoxide (DL(CO)) in healthy subjects.

The study was performed in a randomized, double-blind, placebo-controlled manner. DL(CO) was measured in 22 healthy male volunteers (age 18-25 years) who were randomized to melatonin (n = 11) and placebo administration (n = 11). At baseline, DL(CO), alveolar volume (V(A)) and other spirometric parameters such as forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), peak expiratory flow (PEF) and maximal voluntary ventilation (MVV) were measured. DL(CO) was then corrected for the hemoglobin concentration. Measurements were repeated in a double-blind fashion 60 min after the administration of melatonin (1 mg) or placebo.

DL(CO) was significantly decreased (39.31 +/- 4.75 vs. 34.82 +/- 6.18 ml/min/mm Hg) 60 min after the melatonin administration (p = 0.01), while FEV(1), FVC, FEV(1)/FVC, PEF and MVV values did not demonstrate significant differences. Placebo administration did not result in significant alteration in any of these parameters.

In healthy subjects, oral administration of melatonin acutely influences the DL(CO) without affecting other pulmonary function test results. We conclude that melatonin may have a reducing effect on the DL(CO) in the lungs.