Cells of hibernating animals are compared with those of mammals which do not hibernate to examine basic mechanisms of ion transport and interactions of transport mechanisms which ensure cellular ionic balance. The principal adaptation of hibernators studied so far has been the ability of their cells to function at low temperature. Past effort has documented the involvement of the Na/K pump and of general leak in this adaptation in several tissues (kidney, erythrocytes, brain, liver). Future efforts will focus on erythrocytes.
Our aim i s to define the points of failure in the cold in terms of the pump's kinetics and its overall scheme in cold-sensitive cells of non- hibernators and to exploit unusual features of the pump in hibernator cells for a better understanding of pumps in general. The second objective is to define the differences in the several components of passive permeability to Na between cold-sensitive and cold-tolerant red cells that permit ion balance with reduced active transport at low temperature and to determine how cytoplasmic factors may be involved in bringing pumps and leaks into balance under widely changing conditions. Another adaptation of many hibernators is seasonal inanition and self-starvation. Some species, such as bears and prairie dogs, exhibit this ability even without the concomittant lowering of metabolism by cooling. Studies in human and mammalian red cells have suggested that reduction in energy-dependent membrane transport may be a factor in the energy conservation of the cell during starvation, but this has not been examined in these species which specialize in starvation-adaptation and previous studies have not considered the contribution of reduced permeability as a possibility. We propose to do this. The perceived areas of health-relatedness are, for the low temperature studies, improved viability of cells during storage and, for the seasonal/inantion studies, cellular adaptation to and effects of under-nutrition.
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