Published online by Cambridge University Press: 19 January 2009
1. Twenty pigs were reared to a weight of 90 kg on various dietary regimens so that their lipid content varied from 16 to 38%;. They were injected intravenously with ~ 400 μCi of 42KCl. The animals were killed ~ 28 h after injection and their contents of water, lipid, sodium and potassium were determined.
The specific activity of plasma reached equilibrium 10–12 h after injection, that of urine not until 20 h after.
Losses of activity in urine, faeces and gut contents in the 24 h after injection amounted to 3·1, 0·3 and 1·5% of the injected dose, respectively.
Total body K was more accurately estimated from urine specific activity than from plasma specific activity.
Exchangeable K, estimated from urine specific activity Ke(u), was highly correlated with the weight of fat-free tissue (r = 0·93), the residual standard deviation of the regression being 1·8 kg fat-free tissue.
Percentage extractable fat was equally well correlated with Ke(u) (r = −0·92).