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Plasma concentrations of prostaglandins E₂ (PGE₂) and F_2α (PGF_2α) are studied in venous and arterial blood in 14 healthy subjects and 32 asthmatic patients. In the asthmatic patients we found: (1) a good correlation between PGE₂ concentration in venous blood and the seriousness of the airway obstruction; (2) a good correlation between PGE₂ and PGF_2α in the arterial blood, but not in the venous blood; (3) a decrease in the arterial concentrations of PGE₂ and PGF_2α after fenoterol-induced bronchodilatation, but the variations of PGE₂ and PGF_2α still correlate. None of these results were obtained in normal subjects. It seems that the asthmatic allergic patient has a disorder of the metabolism of prostaglandins in the lungs; however, the results obtained do not allow us to say if it is a causal condition or a metabolic consequence of the bronchospasm. Concerning the venous blood, there could be an increase in the peripheral production of PGE₂ which might result from the hypoxemia following airway obstruction.

The hyperreactivity-modulating effect of SCH 1000 and fenoterol was tested in two groups of 10 patients. The drugs were administered at random, in simple blind fashion. Baseline pulmonary function was in the range of predicted values for all patients. One group received 80 μg of SCH 1000. When the drug was inhaled after carbachol challenge, pulmonary function returned to normal values in all patients. When the drug was inhaled before challenge, a shift to the right of the dose-effect curves was observed in all patients but 1. The other group received 800 μg of fenoterol. When the drug was administered after carbachol challenge, all 10 patients returned to baseline within 10 min. When it was given before carbachol challenge, a shift to the right of the dose-effect curves was observed in 9 patients out of 10. SCH 1000 and fenoterol induced an effective protection against carbachol, increasing the PD20 and shifting the dose-effect curves to the right in most of the asthmatics. In 2 patients, 80 μg of SCH 1000 or 800 μg of fenoterol seemed too low in order to achieve a complete protective effect