Effects induced by saliva of the aquatic hemipteran Belostoma anurum on the isolated guinea-pig heart

Abstract

1. The effects of the saliva of the aquatic hemipteran Belostoma anurum were investigated on the isolated guinea-pig heart, perfused with Locke solution by the Langendorff's method. 2. The electrocardiogram (bipolar lead), the contractile force (g) and coronary flow (ml/min) were simultaneously recorded. 3. The total protein present in the saliva of each belostomatid was 11.17 +/- 2.39 micrograms (N = 10), and SDS-PAGE of the saliva showed a complex protein composition (N = 10). 4. Bolus injections of 0.2 ml saliva obtained from 10 belostomatids elicited complex effects which were divided into two phases (N = 8): an initial phase characterized by sinus bradycardia and/or A-V block associated with a decrease in contractile force and an increase in coronary flow followed by a decrease and a second phase, 0.5-5 min after saliva injection, characterized by a progressive increase in resting tension (ventricular contracture). 5. Since pretreatment of the preparation with atropine or verapamil did not prevent the initial and the late effects (N = 12), we conclude that these effects are not explained either by a muscarinic effect or by a stimulation of calcium channels. 6. Injection of saliva previously mixed with heparin (1000 IU/ml, N = 7), evoked the first but not the second phase (ventricular contracture). 7. Injection of saliva from two belostomatids into the isolated hearts of guinea pigs, not previously treated with heparin, elicited dramatic effects, such as ventricular contracture (N = 6). 8. We suggest that the formation of an acid-base complex (heparin-saliva) would prevent, in part, the toxic effects of the saliva on the heart.