Brasil 1Bothrops jararaca venom (BJV) caused a fall in the carotid artery blood pressure of the anaesthetized snake. This effect was tachyphylactic and was potentiated by captopril, a kininase II inhibitor; it was partially antagonized by promethazine plus cimetidine and was not affected by atropine. 2 Similar hypotensive effects were obtained by administration of trypsin or a partially purified BJV kininogenase to the snake. 3 Incubation of Bothrops jararaca plasma (BJP) with trypsin released a substance (or substances) that produced hypotension in the snake but not in the rat; this hypotensive effect was also potentiated by captopril. 4 The trypsinised plasma contracted Bothrops jararaca isolated uterus, a pharmacological preparation weakly sensitive to bradykinin. Trypsinised plasma was inactive on pigeon oviduct and rat uterus and displayed a weak action on the guinea-pig ileum. Similar effects were observed with incubates of a fraction of BJP, containing globulins, with a partially purified BJV kininogenase. 5 Like mammalian kinins, the substance(s) was(were) dialysable, thermostable in acid but not in alkaline pH, and inactivated by chymotrypsin but not by trypsin. Its(their) inactivation by BJP or BJP kininase II was inhibited by captopril. 6 These findings strongly suggest that, besides releasing histamine, BJV or trypsin release a kininlike substance (or substances) from the snake plasma. 7 Since BJV and other kininogenases active on mammalian plasmas were shown to be unable to release kinins from BJP, in experiments conducted on pharmacological preparations suitable for the assay of mammalian kinins, these data also suggest that the snake Bothrops jararaca, like birds, may have developed its own kallikrein-kinin system.

By means of high voltage electrophoresis experiments it could be demonstrated that the dipeptide hydrolase present in the plasma of Bothrops jararaca is similar to the angiotensin I converting enzyme of human plasma. Therefore, angiotensin I can be considered as a probable natural substrate for this potent snake peptidase in contrast to bradykinin, which is excluded in that case, since this snake plasma was previously found to be deficient in intrinsic kinin releasing system. On the other hand, the presence of angiotensinase activity in this snake plasma could also be demonstrated. Through the pharmacological comparison of angiotensin II with the pressor peptide released from the Bothrops jararaca plasma by chymotrypsin, an indirect indication of the presence of angiotensinogen in the plasma of this reptile was obtained.

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