Temperature sensitivity of the sodium pump in red cells from various hibernator and non-hibernator species

Summary Ouabain-sensitive K influx was measured at 5°C and 37°C in red cells from seven species of mammals known to hibernate, and nine species of non-hibernators. Care was taken to saturate the internal and external cation sites of the sodium pump, and maintain the cell metabolism. Species variation in ouabain-resistance among rodents was also taken into account. In six out of seven species of hibernators the pump was relatively insensitive to lowering the temperature, the ratio of activity at 5°C/37°C being >1.8%. By contrast eight of the nine non-hibernator species gave a ratio <1.8%. The two exceptions were the hamster, which gave a ratio of 0.8% as a hibernator, and the mole which gave a ratio of 3% as a non-hibernator. No similar correlation was observed for the ouabain-insensitive K influx, in either groups of animals. It is concluded that cold tolerance of the sodium pump is a general but not essential property of hibernator red cells.