DAILY RHYTHMS OF RENAL EXCRETION IN ARCTIC-DWELLING INDIANS AND ESKIMOS

¹ Division of Human Physiology, National Institute for Medical Research, (Hampstead Laboratories), London, N.W.3

The daily rhythms of renal excretion of indigenous arctic subjects were recorded under natural conditions during the continuous midsummer daylight (Indians and Eskimos) and in the continuous darkness of midwinter (Indians only). The excretory patterns for water, potassium, sodium and chloride have been compared with those of a group of British control subjects, recorded when they were newly introduced into a summer arctic environment in adult life. In general, the excretory patterns of the arctic subjects contain a high proportion of abnormalities, such that the averaged patterns for the indigenous groups are less well defined than are those for the control group of subjects from a temperate zone. The loss of definition of the rhythms is most marked in the Eskimo subjects, where differences between day and night excretory rates have virtually disappeared.

Mathematical analysis of the individual results shows that the relative amplitude of the rhythm of potassium excretion decreases from British controls summer Indians winter Indians summer Eskimos. The differences between control subjects and all indigenous subjects and between Indians and Eskimos are significant, and cannot be accounted for by variations in age, activity pattern or diet.

It is suggested that the normal daily alternation of light and darkness in the environment is important not only for the day-to-day maintenance of renal diurnal rhythms but also for the initiation and full expression of these rhythms in the early life of the human subject.

Note:

This work was made possible by generous financial aid from the Royal Society and from the Wellcome Trust. I should also like to thank Dr. Laurence Irving and his colleagues at the Arctic Health Research Center, Anchorage, Alaska, who helped me in so many ways and who introduced me to the villages of Old Crow and Wainwright and their interesting and co-operative inhabitants. Finally, I am indebted to Dr. 0. G. Edholm for his helpful criticism of the manuscript.