Effect of hypothermia and ether anesthesia on the dispositions of creatinine and urea in mice

Hypothermal mice were used under the anesthetized condition with ether to clarify the effect of diminished blood circulation on the dispositions of creatinine and urea which are considered to pass through the water-filled pores of biological membranes easily. The total body clearance of each chemical was considerably decreased in hypothermal mice compared with normal mice. This was considered to be caused by the decrease of glomerular filtration rate. The whole-body autoradiograms obtained following intravenous administration of 14C-urea and the rate of muscular blood flow showed that the transfer of urea from blood to muscle was apparently delayed by the decrease of muscular blood flow rate. However, the transfer of creatinine to muscle was not influenced by the change of muscular blood flow rate. This difference between creatinine and urea might be related to the higher permeability of muscular cell membrane to urea than to creatinine.