1. Urea is present in the cells of the proximal convoluted tubule in a concentration higher than that of the blood or than that of the cells of any of the other kidney tubules. 2. Such a condition can only be reconciled to an assumption of an active secretion (excretion) on the part of these cells. 3. Urea also passes through the glomerular filter with the other crystalloids of the blood plasma...

In an earlier publication’ dealing with a micro method for the estimation of urea in blood, I also described a micro method for the estimation of ammonia in blood and in organic secretions. For the determination of the ammonia two analyses are made; in the first the total urea plus ammonia is determined; and in the second the urea alone after the ammonia has been removed by evaporating the bloo...

The Kidd (JK) blood group locus encodes a urea transporter that is expressed on human red cells and on endothelial cells of the vasa recta in the kidney. Here, we report the identification in human erythroblasts of a novel cDNA, designated HUT11A, which encodes a protein identical to the previously reported erythroid HUT11 urea transporter, except for a Lys(44) --> Glu substitution and a Val-Gl...

The Kidd blood group system (ISBT009), identified in 1951, was the ninth blood group system and it is considered the ninth most clinically important. Antigens of the Kidd blood group system are expressed on type 3 glycoproteins, also known as the urea transporter B (UT-B). The JK protein is expressed on red blood cells (RBCs) and in the endothelium of the descending vasa recta and epithelial su...

Our laboratory previously reported that uremic levels of urea inhibit L-arginine (L-Arg) transport into endothelial cells. The present study further investigated this effect. We measured L-Arg transport in cultured bovine aortic endothelial cells with normal or high urea (25 mM). The urea transport inhibitor phloretin abolished the inhibitory effect of urea on L-Arg transport, suggesting a role...

The objective of this study was to determine the comparative changes in the monthly blood urea nitrogen (BUN) concentration, total protein (TP) concentration in blood serum and the body condition score of Nguni cows and heifers raised on sweetveld. Twenty-four clinically healthy animals in different parities, namely Parity 1 (n = 5), Parity 2 (n = 5), Parity 3-6 (n = 9) and heifers (n = 5), wer...

Home hemodialysis is the most cost-effective form of dialysis and is associated with the lowest mortality. Home hemodialysis patients are usually highly motivated, independent, and actively employed. Because of the minimal supervision they require and the fact that they are not in a controlled environment, it is easy to overlook the measurement of their dialysis adequacy. We studied 6 home hemo...

We performed two experiments to determine (1) whether the metabolism and growth of embryonic snapping turtles (Chelydra serpentina) incubating in wet and dry environments are correlated inversely with the concentration of urea inside their eggs, and (2) whether urea accumulating inside eggs might be the cause of reductions in metabolism and growth by embryos. Eggs in the first experiment were i...

Lactatingdairy cows (n=177) fed with grass and corn silage ad libitum kept in pasture, were randomly assigned to evaluate how urea nitrogen in plasma and milk can be related to their pregnancy rate. Blood and milk samples were collected on the artificial insemination (AI) day to evaluate plasma urea nitrogen (PUN) and milk urea nitrogen (MUN) as well as progesterone levels, excluding cows with ...