Vasoconstrictor components in the Arabian Gulf catfish (Arius thalassinus, Ruppell) proteinaceous skin secretion

The Arabian Gulf catfish (Arius thalassinus, Ruppell) produces toxic substances from its skin and from venom glands located near the base of the pectoral fins. Investigation of the pharmacological properties of the skin toxin have previously shown cholinergic vasoconstrictor activity in umbilical arteries. Cholinergic vasoconstriction was confirmed in sheep renal arteries. This activity was partially blocked by atropine, while most of the residual contraction was eliminated by simultaneous addition of indomethacin. Skin toxin treatment of arterial specimens caused a release of prostaglandin (PGE2, TXB2 and 6-keto-PGF1 alpha) into the organ bath. Prostaglandin release was blocked by pretreatment with indomethacin. Heat denaturation of skin toxin caused a loss of only the indomethacin-sensitive muscle contraction activity; most of the residual activity was blocked by atropine.