Cold acclimation in the secretory responses of the isolated exocrine pancreas of the rat.

1. The secretory function of the isolated and perfused exocrine pancreas has been studied in the course of cold acclimation in rats that were fed at an ambient temperature of 1 degrees C in an artificial climatic room.2. A series of experiments was carried out in early autumn (autumn series). The sums of the outputs of protein, amylase, zymogen protease, lipase, and juice flow in samples collected for a total of 30 min during and after 5 min stimulation with different concentrations of cholecystokinin-pancreozymin (CCK-PZ; 5-50 m-u./ml.) were simultaneously measured in the autumn series of experiments, and they were plotted against the logarithmic scale of concentration of CCK-PZ to obtain a dose-response relation.3. The sums of protein output, lipase output, and juice flow evoked by different concentrations of CCK-PZ in the group of rats fed at 1 degrees C for 3 weeks were almost identical to the corresponding value in the group fed at about 21 degrees C for 3 weeks.4. The sum of output of zymogen protease in the former group was almost identical to the corresponding value in the latter group except that the sum induced by 20 m-u. CCK-PZ/ml. was significantly larger in the former.5. The sum of output of amylase induced by various concentrations of CCK-PZ in the former group was significantly smaller than the corresponding value in the latter group.6. It was thus concluded that the CCK-PZ-induced outputs of protein, lipase, and zymogen protease were little affected if any by 3 weeks of cold exposure, whereas the CCK-PZ-induced amylase output was significantly suppressed.7. Another similar series of experiments was performed in the summer of the same year. The results obtained suggest that the secretory function of exocrine pancreas is directly inhibited by prolonged cold exposure in summer but it is not in autumn.