Prostaglandin F-2 alpha functions as a local hormone on human airways

Vasoactive hormones may be classified either as 'local' or as 'circulating', depending on whether they are or are not removed by the pulmonary circulation. Prostaglandin F-2 alpha is partially removed by the human pulmonary circulation. We examined the hypothesis that, with respect to the human lung, PGF-2 alpha functions as a local mediator. Prostaglandin F-2 alpha was given to normal and asthmatic subjects via both intravenous and aerosolized routes, and we measured specific airway conductance, spirometry, functional residual capacity, and closing volume. Aerosolized PGF-2 alpha induced significant changes of all measured parameters in both normals and asthmatics, while intravenous PGF-2 alpha-induced changes were limited to the FVC in both normals and asthmatics. The data suggest that intravenous PGF-2 alpha induced constriction of peripheral lung units. The greater sensitivity of the peripheral lung units of asthmatics versus normals to PGF-2 alpha, suggest that the increased sensitivity of airway smooth muscle of asthmatics versus normals to PGF-2 alpha is not restricted to the conducting airways, but extends to the smooth muscle of the peripheral lung units. The data is consistent with the hypothesis that, with respect to the lung, PGF-2 alpha functions as a local hormone, but, furthermore, suggest that, possibly of greater importance than the definition of a hormone as 'local' or 'circulating', is the definition of the intrinsic properties of the muscles on which the hormone is exerting its effects.