The potassium and sodium contents of sheep tissues in relation to the potassium content of the erythrocytes and the age of the animal

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Abstract
Potassium and sodium concentrations in kidney, heart and liver tissue in sheep with either high (HK) or low (LK) concentrations of K in their erythrocytes were determined in young, adult and aged animals. The concentration of Na in the cortex of the kidneys of LK animals was significantly higher (about 5.6%) than in those of NK animals. Differences of the order of those found in the erythrocytes of sheep were, however, not found in any tissue. The concentration of K decreased with age in both kidney and heart but not in the liver; the average difference between young and aged sheep was 5.7% in the kidney and 6.9% in the heart. A reciprocal rise in Na occurred in the kidney and the average difference between young and aged sheep was 7.4%. The ratio of K to Na decreased significantly with advancing age in kidney and heart tissue. Nine tissues were analyzed from another 5 LK and 5 HK aged ewes. The skeletal muscle, liver, spleen and kidney (expressed on a fat- and blood-free basis) of the aged HK ewes tended to have higher concentrations of K(1.52.2, 3.6 and 1.9% respectively) and lower concentrations of Na (10.7, 12.3, 9.2 and 4.8% respectively) than those of the aged LK ewes. Rumen epithelium from LK sheep had a significantly lower K concentration (19.5%) than that from HK animals. The fat content of the skeletal muscle of aged LK sheep was significantly higher (17 g of fat/kg wet wt. or about 48%) than that of aged HK sheep but this difference was not found in a group of lambs of the same breed.