It has been well documented that a negative relationship exists between blood, plasma, or milk urea nitrogen and fertility in dairy cattle, with increased concentrations of plasma urea nitrogen (PUN; > 19 mg/dL) and milk urea nitrogen (MUN; > 15.4 mg/dL) being associated with suppressed fertility. Although this relationship is not fully understood, likely contributing factors have been suggeste...

Although the mammalian urinary tract is generally held to be solely a transit and storage vehicle for urine made by the kidney, in vivo data suggest reabsorption of urea and other urine constituents across urinary tract epithelia. To determine whether urinary tract tissue concentrations are increased as a result of such reabsorption, we measured urea nitrogen and creatinine concentrations and d...

Urea rebound refers to an early postdialysis phenomenon in which urea returns to the systemic circulation, raising the blood level to a near plateau over a period of 0.5 to 1 hour [1]. The urea involved is believed to have come from either the intracellular compartment by means of diffusion resulting from the dialysis-induced concentration gradient [2,3], or tissues poorly perfused as a result ...

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...

Investigations using ammonium citrate-(15)N and urea-(15)N showed that children in the acute stage of kwashiorkor and marasmus receiving a diet of adequate protein content retained a considerable percentage of the label from both compounds. Excretion of both total (15)N and urea-(15)N was subnormal and elimination was virtually completed 36 hr after administration of the isotope. During recover...

Thirty-seven young healthy subjects with normal renal function were studied to assess the quantitative effect of protein intake on creatinine clearance. A standard 24-h urine collection and blood sample at the end of the collection were obtained for creatinine and urea concentrations. Correlations between creatinine clearance and urinary urea nitrogen excretion (r = 0.8; P less than 0.0001) and...

The present study was aimed to observe the effects of urea ingestion, non-protein nitrogen, on the disorder of nitrogen metabolism with the L-carnitine contents using the blood, kidney, liver, and femoral muscle as markers. A total of 8 Japanese white rabbits were used in this experiment. They were fed a basal diet prepared for the control group and the nitrogen volume proportionated to one-thi...

According to the usually accepted concept, the urea removed from the blood by the kidneys is excreted in two forms, chiefly as urea itself, but partly as ammonia. That the ammonia of the urine is formed in the kidneys was demonstrated by Nash and Benedict (1921), in work which has been confirmed by other authors (cf. Peters and Van Slyke, I, p. 373). Evidence from animal experiments in v4vo has...