A comparison of the role of kinins and serotonin in endotoxin induced fever and Trypanosoma vivax infections in the goat.

Goats were infected with Trypanosoma vivax or inoculated with a low pyrogenic dose of lipopolysaccharide (LPS) obtained from Escherichia coli or Salmonella typhimurium in order to obtain evidence about the role of kinins and serotonin in the pathogenesis of trypanosomiasis and in endotoxin induced ruminal stasis. The following conclusions were made: (1) whole blood serotonin and bradykinin-like activity levels and clinical symptoms during fever, induced by LPS E coli or T vivax infection are not comparable. (2) There is no good correlation between the changes in heart rate and the temperature rise during fever, evoked by LPS E Coli or T vivax infection. (3) No change of whole blood serotonin level was found during LPS induced fever and only a small increase in the whole blood bradykinin-like activity could be detected. These data suggest that the inhibition of the extrinsic ruminal contractions and the bradycardia followed by a biphasic increase in heart rate during LPS induced fever are not mediated by these substances. (4) The peaks of parasitaemia during the acute phase of T vivax infection are associated with increases in whole blood bradykinin level. However, the high blood bradykinin-like activity did not cause an inhibition of the extrinsic ruminal contractions. (5) The slightly raised bradykinin-like activity during the chronic phase of T vivax infection suggests that bradykinin is not a major factor in the pathogenesis of chronic T vivax infection. (6) The fluctuations of the blood serotonin level during temperature peaks, associated with peaks of parasitaemia and the presence of many platelet thrombi in goats dying during overwhelming parasitaemia suggests a correlation between T vivax, platelet aggregation and blood serotonin decrease.