Lung mast cell hyperplasia and pulmonary histamine-forming capacity in hypoxic rats.

KAY, JOHN MICHAEL, JACK C. WAYMIRE, AND ROBERT F. GROVER. -Lung mast cell h..perplasia and pulmonary histamine-forming capacity in hypoxic rats. Am. J. Physiol. 226(l): 178-184. 1974.We have studied lung mast cells (MC), histamine, and pulmonary histamine-forming capacity (PHFC) in acute and chronic hypoxic pulmonary hypertension in rats. Histochemical examination of lung tissue showed no evidence of histamine depletion of perivascular MC in six rats subjected to acute hypoxia in a decompression chamber simulating 5,500 m altitude. In contrast, intravenous injection of compound 48/80 into five rats produced degranulation and histamine depletion of pulmonary MC within 2 min. Chronic hypoxia for 20 days increased the mean lung MC density in eight rats to 7.65 & 1.23/mm2, compared with 2.97 & 0.48/mm2 in nine untreated controls. PHFC was not increased by chronic hypoxia. There was a linear logarithmic relation between lung MC density and right ventricular weight (an index of pulmonary hypertension) in control and chronically hypoxic rats. Although we have not demonstrated histamine release from lung MC during brief periods of acute hypoxia, our data support the idea that the perivascular lung MC may be concerned in the mediation of the pulmonary pressor response to chronic hypoxia.