Airway effects of slow reacting substance, prostaglandin F2alpha and histamine in the guinea-pig.

SRS, PGF2chi, and histamine were administered intravenously or as aerosols to artifically ventilated guinea-pigs in order to asses their capacity to affect tracheal insufflation pressure measured by means of Konzett-Rössler technique, Independently of route of administration all three compounds increased tracheal insufflation pressure, SRS being the most potent one. Bilateral cervical vagotomy did not alter the effect. Relative to histamine SRS and PGF2chi were considerably more active by aerosol administration than by intranvenous injection. The aerosols had little or no effect on systemic blood pressure. On intravenous injection, histamine decreased and SRS and PGF2chi increased arterial blood pressure in a dose-dependent fashion. The airway effects of histamine were correlated to those on blood pressure whereas with SRS and PGF2chi this was not seen when the blood pressure effects were marked. Preadministration of adrenaline or isoprenaline as aerosols antagonized the increase in insufflation pressure, but not the effects on blood pressure, produced by intravenously injected histamine or PGF2chi. It is concluded that SRS, PGF2chi and histamine on intravenous or aerosol adminstration increase tracheal insufflation pressure in the guinea-pig mainly by an action on airway tone. The data emphasize that SRS is a potent bronchoconstricting agent, possibly of pathophysiological significance in guinea-pig anaphylaxis.