Seasonal variation of magnesium and calcium in serum of the hypothermic rat

¹ Department of Zoology, The University, Hull, England

Records of changes in blood Mg and Ca during body cooling are conflicting. Although a rise in serum magnesium is established in hibernators and with less certainty in artificially cooled animals, some workers have associated these changes with CO₂ accumulation. In the present experiments rats were cooled to a rectal temperature of 15 C with artificial respiration to prevent CO₂ accumulation. Cardiac arrest did not occur. A mean 24% rise in serum magnesium was found in the winter months. A fall occurred in the summer but the mean figure for these months was not significant. No change in the calcium levels was observed. The possible significance of the findings is discussed.