Kallikrein, nitric oxide and the vascular responses of the submaxillary glands in rats exposed to heat.

Abstract

During exposure of normal rats to an ambient temperature of 36 degrees C or 40 degrees C, body temperature increases; thermolytic processes are set up and saliva is spread on the skin. In Wistar rats, thermolytic salivation started when body temperature was above 39 degrees C. This water loss was associated with a loss of body weight. A 10% reduction of plasma volume was observed in animals exposed to 40 degrees C but no change was observed in those exposed to 36 degrees C. Body weight loss was reduced by hexamethonium, atropine, prazosin, HOE 140, a bradykinin-antagonist, and NG-nitro-L-arginine (NOARG), a NO synthase inhibitor. The weight and blood content of the submaxillary glands, which are the main effectors of the thermolytic processes, increased as a function of the ambient temperature. The increase of blood content was enhanced by hexamethonium but reduced by atropine and NOARG. The weight increase was inhibited by hexamethonium, prazosin, HOE 140 and NOARG. At an ambient temperature of 40 degrees C, a large swelling developed around the submaxillary glands, resulting in a distention of the surrounding soft tissues. This local oedema fluid contained low levels of endogenous proteins but accumulated exogenous labelled albumin. This swelling was enhanced by atropine but decreased by hexamethonium, trasylol, HOE 140, NOARG, ketoprofen, a cyclooxygenase inhibitor, and prazosin. In kininogen deficient rats, the blood content of submaxillary glands increased as a function of ambient temperature. No increase in glandular weight and no swelling of the of the soft tissues were observed. After atropine, the weight of the glands increased and a swelling of the soft tissues appeared.(ABSTRACT TRUNCATED AT 250 WORDS)