Inhibitory action of the defensive discharge of the grasshopper, Poecilocerus pictus, on certain enzymes in the lizard, Calotes nemoricola.

Administration of the defensive secretion of the grasshopper, Poecilocerus pictus inhibited acetyl-cholinesterase (AChE) and adenosine triphosphatases (ATPases) in the brain and muscle tissues of the garden lizard, Calotes nemoricola. The inhibition was gradual, continuous and irreversible with lethal doses of the defensive secretion, whereas the inhibition observed with sublethal doses was followed by an increase towards control levels within 24 h after injection. In vitro application of defensive secretion also showed concentration-dependent inhibition in the activity of AChE and ATPases in the tissue homogenates. Inhibition in AChE activity might be a factor for the observed mortality is the defensive fluid-treated lizards. Since the cardenolides are known to inhibit the activity of ATPases, the inhibition in the activity of ATPases observed in the present study suggests the presence of cardenolides in the defensive fluid of P. pictus.