Serum Amino Nitrogen Concentration in Different Parts of the Vascular System

During investigations on amino nitrogen transport in the body a few studies were made on the amino nitrogen level in blood as it courses the vascular system. The observations were on dogs under nembutal anesthesia after they had been fed Purina Dog Chow exclusively for one to 2 weeks and then fasted 24 hours. Venous blood samples, except those from the femoral vein, were obtained by passing a long straight cannula with a closely fitting stilet through an opening in the external jugular vein, down through the right auricle to the lower part of the inferior vena cava. Specimens were first taken from the lower and upper parts of the inferior vena cava (below and above the renal veins). With a little manipulation the cannula could then be placed and held snugly in a branch of the hepatic vein and venous blood from the liver thus obtained. Finally samples were removed from the right heart and superior vena cava. Three workers could obtain the 7 samples of blood, including the arterial, almost simultaneously. Blood was promptly centrifuged and amino nitrogen determinations made on the serum in duplicate by a modification of the Folin method.

The results are presented in Table I. In 4 (Nos. 1 to 4) the amino nitrogen in the venous blood from the liver was definitely lower than the arterial level. These have been averaged to contrast with 7 (Nos. 5 to 11) in which blood from the liver was approximately the same as the arterial. The averages are recorded graphically in Fig. 1. The magnitude of the changes is noteworthy.

There was, as a rule, a distinct rise in amino nitrogen concentration as blood passed from artery to the femoral vein and a further rise in the lower part of the inferior vena cava.