Pharmacological studies of jumper ant (Myrmecia pilosula) venom: evidence for the presence of histamine, and haemolytic and eicosanoid-releasing factors.
Jumper ant venom was prepared by extraction of venom sacs in distilled water and centrifugation to remove insoluble material. Jumper ant venom (2 micrograms/ml) produced a biphasic response on isolated guinea-pig ileum, i.e. an initial rapid contraction followed by a slower prolonged contraction. The histamine antagonist mepyramine (0.1 microM) inhibited the first phase of this response by greater than 90%. In the isolated rat stomach fundus strip (which is insensitive to histamine), jumper ant venom (6 micrograms/ml) produced only a single contraction. No tachyphylaxis was observed to repeated doses of jumper ant venom in guinea-pig ileum or rat fundus strip. Responses to jumper ant venom of the egg-albumin-sensitised guinea-pig ileum were not significantly different before and after an in vitro anaphylactic response induced by egg albumin (0.5 mg/ml). Fluorometric assay revealed a mean value of 0.9 +/- 0.2% of the dry weight as histamine in jumper ant venom. Both the lipoxygenase/cyclo-oxygenase inhibitor BW755C and the cyclooxygenase inhibitor indomethacin significantly inhibited the second phase response to jumper ant venom of the guinea-pig ileum, and the response of the rat fundus strip. The muscarinic receptor antagonist atropine (0.1 microM), the bradykinin antagonist [Thi5,8,D-Phe7]-bradykinin (10 microM) and the angiotensin converting enzyme inhibitor captopril (20 microM) did not affect either phase of the venom response in guinea-pig ileum. Jumper ant venom caused haemolysis of guinea-pig blood. The degree of haemolysis was significantly reduced when boiled venom was used. These results suggest that jumper ant venom contains histamine and may cause the release of cyclo-oxygenase products. It also contains a heat-sensitive haemolytic factor.
Matuszek
M A
MA
Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
Hodgson
W C
WC
Sutherland
S K
SK
King
R G
RG
D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine / Q000494:pharmacology; D000109:Acetylcholine / Q000032:analysis; D000818:Animals; D000862:Ant Venoms / Q000032:analysis / Q000494:pharmacology*; D001920:Bradykinin / Q000032:analysis; D004386:Duodenum / Q000187:drug effects; D015777:Eicosanoids / Q000378:metabolism*; D006168:Guinea Pigs; D006461:Hemolysis / Q000187:drug effects*; D006632:Histamine / Q000032:analysis*; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence
D000862:Ant Venoms; D015777:Eicosanoids; D015772:4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyrazol-3-amine; D006632:Histamine; D000109:Acetylcholine; D001920:Bradykinin