The “continuing” metabolism of nitrogen in animals

Abstract

It has been known since the time of Voit that in passing from a high to a low level of nitrogen intake, or vice versa, there is a lag, which in rats, for example, may last as long as a month before equilibrium at the new low level is established. Martin and Robison (1922) pointed out that the logarithm of the difference between the daily nitrogen excretion at the low level, designated as x , and the daily excretion in the interval between the two levels, a, i. e ., log ( a-x ), plotted against time gives a straight line. The same relationship is demonstrable in the data of the experiment of Deuel, Sandiford, Sandiford, and Boothby (1928). This logarithmic relation indicates that the decomposition of the nitrogen represented by ( a - x ), which we shall term the continuing metabolism, resembles a first-order reaction. The following question arises out of this phenomenon, which, so far as the writers are aware, has been given little attention. “ Is the continuing metabolism suspended during the period when nitrogen equilibrium is being maintained by the ingestion of the larger quantity of protein, or does it persist at a rate indicated by the extrapolated value of log ( a-x ) to zero time ? ” If the second alternative be true, it follows that in the state of nitrogen equilibrium there is storage of a portion of the exogenous nitrogen corresponding to the extent of the continuing metabolism.

Plasma Protein Metabolism—electrophoretic Studies

“…Tables 6 and 6 FzG. 4. Electmphorefic patterns d u n g recovery from severe acute plasma protein depletion complicated by hemolytic reaction.…”

Catabolic Rate of Body Protein in Adult Rat over an Entire Period of Protein Depletion

“…All the animals were preliminarily fed a stock diet containing 20~;; of casein for 8 days. The animals of the control group were sacrificed for assay at the end of this period and others were given a protein-free diet thereafter.…”