Some Effects of Cold-Acclimation on the Biochemistry and Histology of the Hamster Kidney.

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Abstract
Summary The effects of cold acclimation on the kidney of the adult male hamster (Mesocricetus auratus) were studied. The animals were exposed to an ambient temperature of 4°C for periods of 4 to 10 weeks. Biochemical changes induced by cold acclimation include: 1) increased succinoxidase and succinic dehydrogenase activity, 2) increased total microsomal DPNH-cytochrome c reductase activity per kidney, but a decreased specific activity of this enzyme, and 3) increased total nitrogen, microsomal nitrogen, and DNA. The activity of glutamicoxaloacetate transaminase is unchanged. The wet weight of the kidney is much greater in cold-acclimated than in control animals, but decreases in heat stress. Thus, renal growth in the cold-acclimated animals probably is not simply a response to stress. Kidney growth is the same in cold-acclimated males and females, indicating that gonadal hormones are not specifically involved. Striking histological changes occur very soon after the animals are exposed to cold. After 2 days of cold-exposure, mitotic figures and multinucleate cells appear, especially in the proximal tubule. Between the fourth and tenth days, the number of mitosing cells remains fairly constant, but the number of multinucleate cells increases. Quite a few binucleate and, less frequently, tetranucleate cells appear. In a few cells, clusters of 6 nuclei were observed. After 8 weeks of exposure, mitosis has ceased and multinucleate cells are very uncommon. The tubules are dilated in some areas, diminished in size or, quite frequently, even occluded in others. These areas alternate, and probably are areas of hyperemia and ischemia, respectively. There is hyaline degeneration and angiomatous stroma in the cortico-medullary junction zone. Albuminous casts are common. The number of cells in the glomeruli is conspicuously high. The kidneys appear to have quite a few of the classic characteristics of renal hypertension, but sclerosis per se is not detectable in most of the acclimated animals.