Urine retinol-binding protein

Monitoring of Cd exposure can take place by the determination of Cd in whole blood (reflects recent exposure) or urine (reflects body burden) by GF-AAS. Early effects can be monitored by the determination of a tubular protein (e.g. 132-microglobulin, retinol binding protein, a2-microglobulin) or the activity of an enzyme (e.g. N-acetyl 3-D-glucosaminidase) in urine. 

Donaldson MD, Chambers RE, Woolridge MW, Whicher JT (1989) Stability of alpha-1-microglobulin, beta-2-microglobulin, and retinol binding protein in urine. Clin Chim Acta 179 73-77... 

Thyroid hormones have a lengthy life-span in the bloodstream — several days — probably because they are bound to proteins in the circulation. More than of T4 and T3 is bound to plasma proteins. These prolerns arc thyroid hormone-binding protein, transthyretin, and albumin. Most of the hormone is carded by thyroid hormone-binding protein. Transthyretin (from thyroid and retinol) occurs in a Irl complex with retinol-binding protein In the bloodstream. This complex serves to prevent the loss of retinol-binding protein, which is a small protein, in the urine. Transthyretin has also been called prealbumin, it binds T4 and not TJ,... 

Urine Urinalysis with microscopic examinination of urine sediment Albumin Retinol binding protein N-acetyl-p-D-glucosaminidase Alanine aminopeptidase Osmolality Creatinine Glomerulus Proximal tubule Proximal tubule Proximal tubule Distal tubule Control for urine concentration... 

Vitamin A is readily absorbed from the intestine as retinyl esters. Peak serum levels are reached 4 h after ingestion of a therapeutic dose. The vitamin is distributed to the general circulation via the lymph and thoracic ducts. Ninety percent of vitamin A is stored in the liver, from which it is mobilized as the free alcohol, retinol. Ninety-five percent is carried bound to plasma proteins, the retinol-binding protein. Vitamin A undergoes hepatic metabolism as a first-order process. Vitamin A is excreted via the feces and urine. Beta carotene is converted to retinol in the wall of the small intestine. Retinol can be converted into retinoic acid and excreted into the bile and feces. The elimination half-life is 9 h. 

Beetham R, Dawnay A, Landon J, Cattell WR. A radioimmunoassay for retinol-binding protein in serum and urine. Clin Chem 1985 31 1364-7. 

Bernard AM, Moreau D and Lauwerys R (1982) Comparison of retinol-binding protein and fS-2-micro ohulin determination in urine for the early detection of tubular proteinuria. Clin Chim Acta 126 1-9. 

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