[Heat-induced salivary gland hypertrophy: change during chronic heat exposure (34 degrees C). (author's transl)]

1 A slight rise in ambient temperature (34 degrees C) increased saliva secretion in the rat and this was accompanied by licking behavior, thus increasing heat loss by evaporation. 2 The rise in ambient temperature was accompanied by a hypertrophy of the submaxillary glands (Fig.1, 2), arising from activation of seromucous acini (Fig. 4, 5). 3 The hypertrophy reached a maximum after 2 to 4 days of heat exposure (Fig. 2); it was followed by a slow decrease. Normal values were obtained only after at least 3 weeks in the climatic chamber (Fig. 2, 3), which agreed with behavioral observations. Increased secretion of saliva may help to increase heat loss and maintain survival in a hot environment. 4 The absence of morphological changes in the sublingual g and and the evolution of the granular circonvoluted tubules (Fig. 6) contrast greatly with the hypertrophy of the submaxillary acinus. It is possible that heat-induced saliva secretion may be controlled by both sympathetic and parasympathetic systems.