Hypoxic Pulmonary Vasoconstriction: MODIFYING FACTORS
Several important factors modify hypoxic vasoconstriction (Table 1). While the effects of many of these factors have been repeatedly substantiated, the mechanisms of action remain largely unexplained.
Although the AHPR is present in the lungs of all mammalian species examined, there is considerable species variation in the magnitude of the response. Pigs and cows have a very vigorous response, while dogs and hamsters have a comparatively mild pressor response to alveolar hypoxia. This variability extends to individuals within a given species and among human subjects where significant differences in the strength of the response suggest the influence of unknown genetic factors. A genetic influence on the magnitude of the response is also apparent in animal studies of the adaptation to high altitude. Strains of cattle susceptible to the development of pulmonary hypertension at high altitude (“brisket disease”) have a larger acute hypoxic pressor response than nonsusceptible cattle. Different strains of rats exhibit differences in the magnitude of the response and in their susceptibility to the development of pulmonary hypertension at high altitude.










