Water losses induced by heat exposure and the kinin system in the rat

Normal Wistar rats, normal and kininogen-deficient Brown Norway rats were kept at ambiant temperatures of 26 degrees C, 36 degrees C or 40 degrees C for 3 to 5 hours. Their colonic temperatures and body weights were measured. At 26 degrees C, the changes in these parameters were similar in the three strains. At 36 degrees C, body weight loss was increased more in normal rats than in kininogen-deficient rats. At 40 degrees C, body temperature increased more quickly and body weight loss was less enhanced in kininogen-deficient rats than in normal rats. The water content of muscles was less reduced in kininogen-deficient rats than in normal rats. HOE 140, a bradykinin antagonist, reduced the weight loss of Wistar rats kept at 36 degrees C and 40 degrees C. Atropine or removal of submaxillary glands increased colonic temperature and reduced the weight loss of Wistar rats at 36 degrees C and 40 degrees C. HOE 140 did not modify the reduction of weight loss induced by atropine but increased colonic temperatures and decreased thermal tolerance of atropinized Wistar rats at 36 degrees C. These results indicate that the kallikrein-kinin system plays a role in salivary secretion and in heat exchange during a heat exposure.