Autacoid and anaphylactic reactivity of pulmonary and hepatic smooth musculature of the cat.

Histamine, 2-methylhistamine (2-MeH: a relatively specific H1 receptor agonist), 5-HT, carbachol, bradykinin (BK) and PGF2alpha contract isolated cat pulmonary vein, artery and hepatic vein. PGE1, PGF2alpha and 4-methylhistamine (4-MeH: a relatively specific H2-receptor agonist) contract pulmonary arterial strips but further increase in the dose of PGE1 produces relaxation. Isoproterenol relaxes partially contracted blood vessels at low doses, but contracts at high doses. Cat trachea contracts to 5-HT, acetylcholine and carbachol but is insensitive to histamine, its analogues, BK and PGF2alpha. However, partially contracted trachea relaxes to histamine, 4-MeH, 2-MeH, isoprenaline, BK, PGE1, E2 and F2alpha. PGF2alpha and SRS-A contract cat bronchus. Isoprenaline, PGE1 and E2 relax cat bronchus contracted to carbachol, 5-HT, PGF2alpha, SRS-A and antigen. The in vitro anaphylactic contraction (Schultz-Dale reaction) of isolated pulmonary and hepatic veins, bronchus and trachea from horse plasma sensitized cat suggested the involvement of lung and liver in anaphylaxis of the cat.