Effects of acute or chronic exposure to cold on the lysosomal enzyme system in rat tissues

Abstract

To investigate the effect of cold exposure on the lysosomal enzyme system in brown adipose tissue (BAT), liver, or kidney, 38 male Wistar rats were divided into the following four groups: (1) acute-cold-exposed rats at −5°C for 1 h; (2) cold-acclimated rats at 5°C for 4 weeks; (3)cold-adapted rats by rearing at 5°C for 40 successive generations; and 94) warm-acclimated rats at 25°C (controls). The activities of the four lysosomal hydrolases measured [β-glucronidase, arylsulphatases A and B, and cathepsin D] in both BAT and liver from cold-acclimated and cold-adapted rats showed the same trends, namely, significant increases with one exception (β-glucronidase in cold-acclimated rats) as compared with warm-acclimated rats. The activity of N -acetylglucosamine-1-phosphotransferase, which generates a recognition marker for intracellular transport of the hydrolases to lysosomes via the Golgi apparatus, increased significantly only in BAT from cold-acclimated rats, but decreased markedly, though unexpected, in liver from cold-adapted rats. On the other hand, the activity of N -acetylglucosamine phosphodiester α- N -acetylglucosamidase, which is another key enzyme for generation of the recognition marker, did not vary substantially throughout the experiments. Each exposure to cold appeared to rather reduce the activities of the lysosomal hydrolases in kidney. These results suggest that acute or chronic exposure to cold, in particular the latter, significantly affects the lysosomal enzyme system in rat BAT, liver, or kidney, and that the responses of each enzyme system are different from one another.