EFFECTS INDUCED BY SALIVA OF THE AQUATIC HEMIPTERAN BELOSTOMA-ANURUM ON THE ISOLATED GUINEA-PIG HEART

1. The effects of the saliva of the aquatic hemipteran Belostoma anuru m were investigated on the isolated guinea-pig heart, perfused with Lo cke solution by the Langendorff's method, 2. The electrocardiogram (bi polar lead), the contractile force (g) and coronary flow (ml/min) were simultaneously recorded. 3. The total protein present in the saliva o f each belostomatid was 11.17 +/- 2.39 mug (N = 10), and SDS-PAGE of t he saliva showed a complex protein composition (N = 10). 4. Bolus inje ctions of 0.2 ml saliva obtained from 10 belostomatids elicited comple x 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 follow ed by a decrease and a second phase, 0.5-5 min after saliva injection, characterized by a progressive increase in resting tension (ventricul ar contracture). 5. Since pretreatment of the preparation with atropin e or verapamil did not prevent the initial and the late effects (N = 1 2), we conclude that these effects are not explained either by a musca rinic effect or by a stimulation of calcium channels. 6. Injection of saliva previously mixed with heparin (1000 IU/ml, N = 7), evoked the f irst but not the second phase (ventricular contracture). 7. Injection of saliva from two belostomatids into the isolated hearts of guinea pi gs, not previously treated with heparin, elicited dramatic effects, su ch as ventricular contracture (N = 6). 8. We suggest that the formatio n of an acid-base complex (heparin-saliva) would prevent, in part, the toxic effects of the saliva on the heart.