Pharmacological studies of the venom of an Australian bulldog ant (Myrmecia pyriformis)

Abstract

The purpose of this study was to examine some of the pharmacological actions of venom from the Australian bulldog ant Myrmecia pyriformis. M. pyriformis venom was prepared by extraction of venom sacs in distilled water and centrifugation to remove insoluble material. Venom (2 micrograms/ml) produced a biphasic response of 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 approximately 80%. In the isolated rat stomach fundus strip (histamine-insensitive), venom (2-4 micrograms/ml) produced only a single contraction. Responses to venom of egg-albumin-sensitized guinea-pig ileum, were not significantly different before and after an anaphylactic response induced in vitro by egg albumin (0.5 mg/ml). Fluorometric assay showed that histamine accounted for 3.5 +/- 0.5% of the dry weight of M. pyriformis venom. Both the lipoxygenase/cyclooxygenase inhibitor BW755C and the cyclooxygenase inhibitor indomethacin significantly inhibited the response to venom of guinea-pig ileum (second phase) and rat fundus strip. M. pyriformis venom caused hemolysis of guinea pig blood. The degree of hemolysis was reduced significantly when boiled venom was used. No evidence was found that the venom contains acetylcholine, bradykinin, or 5-hydroxytryptamine or that the venom releases histamine from guinea-pig ileum. However, the results indicate that the venom contains histamine-like activity. In addition the venom was found to cause the release of cyclooxygenase products and to contain a heat-sensitive hemolytic factor.

Diversity of peptide toxins from stinging ant venoms

“…In South Eastern Australia around 2.7% of the population are allergic to Myrmecia pilosula venom, with approximately 50% of allergic people experiencing life-threatening reactions (Brown et al, 2003). The toxicity of the venom appears to result from the presence of a variety of histamine-like, haemolytic and eicosanoid-releasing factors, peptides such as pilosulins, and enzymes including phospholipases, hyaluronidase, and phosphatases (Matuszek et al, 1994a(Matuszek et al, , 1992(Matuszek et al, , 1994bMcGain and Winkel, 2002).…”

A comprehensive portrait of the venom of the giant red bull ant, Myrmecia gulosa , reveals a hyperdiverse hymenopteran toxin gene family

“…Cavill et al showed that (i) the venom of M. gulosa is primarily polypeptidic [with a small amount of histamine (~2%)], (ii) at least eight distinct polypeptide fractions could be separated by electrophoresis, and (iii) multiple distinct biological activities are associated with some of these polypeptide fractions, namely, hyaluronidase, kinin-like, and hemolytic activity. Further studies have since revealed that the venoms of other species of Myrmeciinae are similarly polypeptidic (6)(7)(8)(9)(10)(11)(12), as are those of ants of at least seven other subfamilies, namely, Amblyoponerinae (13), Dorylinae (14), Ectatomminae (15), Myrmicinae (16), Paraponerinae (17), Ponerinae (18), and Pseudomyrmecinae (19).…”

Neuroretinitis following bull ant sting

“…The venom contains histamine-like activity, a heat-sensitive haemolytic factor and causes the release of cyclooxygenase products 7. We felt it was unlikely that the venom was responsible for this patient's ocular presentation because it was unilateral, presented some time after the sting and has not been reported previously despite bull ant stings being relatively common.…”