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Effects of Exercise and Diet on Nitrogenous Constituents in Several Tissues of Adult Rats^1,2,

Department of Animal Science, Macdonald College, Province of Quebec, Canada

The effects of exercise and dietary protein level on amounts of DNA, RNA and total nitrogen in livers, gastrocnemius muscles and skin samples, and on serum albumin-to-globulin ratios were examined. The purpose was to test the stability of DNA and hence the validity of nitrogen-to-DNA and RNA-to-DNA ratios where exercise of various durations was imposed; also to evaluate the hypothesis that exercise might reduce protein reserves by converting labile to stable nitrogen compounds, and that protein in excess of the maintenance requirements might compensate for this conversion. One group of rats was preconditioned by intermittent periods of exercise prior to this test while two other groups underwent no previous exercise. The one-month period of exercise imposed during this test led to reduced serum albumin-to-globulin ratios. Feeding a sub-maintenance protein diet had the same effect, but in combination these treatments did not result in a greater decrease. Preconditioning brought about a marked elevation of plasma globulin level. Preconditioned rats when exercised during this trial had greatly increased amounts of DNA, RNA, and total nitrogen in their gastrocnemius muscles. This increase did not occur in rats exercised daily for 28 days. Liver DNA content was increased in the preconditioned group. Neither exercise nor diet brought about statistically significant changes in skin composition. It was concluded that albumin-to-globulin ratios and DNA ratios could give misleading results in comparisons of exercised and idle rats.

² Financial support for this work was received from the Defence Research Board, Canada Department of National Defence.

³ Present address: Department of Animal Science, University of Saskatchewan, Saskatoon, Saskatchewan.

Manuscript received 10 December 1964.