Retinol urinary

Studies of renal function in stainless steel welders, whose exposure is mainly to chromium(VI) compounds, were negative. Stainless steel welders had significantly increased (p<0.001) levels of urinary chromium, increased clearance of chromium, and increased serum creatinine compared with controls, but no differences were found in the levels of retinol binding protein, p2-microglobulin or other indices of kidney damage (Verschoor et al. 1988). Similar negative results were found in another group of stainless steel welders (Littorin et al. 1984). 

Occupational exposure to chromium(III) or chromium(O) does not appear to be associated with renal effects. No renal impairment based on urinary albumin, retinol binding protein, and renal tubular antigens was found in 236 workers employed in the ferrochromium production industry where ferrochromite is reduced with coke, bauxite, and quartzite. The mean airborne concentration of chromium in various sample locations was 0.075 mg chromium(III)/m3 chromium(VI) was below the detection limit of 0.001 mg chromium(VI)/m3 at all locations (Foa et al. 1988). Workers employed in an alloy steel plant with a mean exposure of 7 years to metallic chromium at 0.61 mg chromium(0)/m3 and to other metals had normal urinary levels of total protein and p2-microglobulin, enzyme activities of alanine-aminopeptidase, N-acetyl-P-D-glucosaminidase, gammaglutamyl-transpeptidase, and P-galactosi-dase (Triebig et al. 1987). In boilermakers exposed to chromium(O), no increase in urinary levels of... 

Twyman SJ, Overton J, Rowe DJ (2000) Measurement of urinary retinol binding protein by immunonephelometry. Clin Chim Acta 297 155-161... 

RBP forms a 1 1 complex with the tetrameric thyroxine-binding prealbumin, transthyretin. This is important to prevent urinary loss of retinol bound to the relatively small RBP (Mr 21,000), which would be filtered by the glomerulus transthyretin has an Mr of 54,000 hence, the complex will not normally be filtered, ffowever, moderate renal damage, or the increased permeability of the glomerulus in infection, may result in considerable loss of vitamin A bound to RBP-transthyretin. 

A mild infection, such as measles, commonly triggers the development of xerophthalmia in children whose vitamin A status is marginal. In addition to functional deficiency as a result of impaired synthesis of RBP (Section 2.2.3) and transthyretin in response to infection, there may be a considerable urinary loss of vitamin A because of increased renal epithelial permeability and proteinuria, permitting loss of retinol bound to RBP-transthyretin. The American Academy of Pediatrics Committee on Infectious Diseases (1993) recommended vitamin A supplements for aU children who have been hospitalized with measles. 

Excessive doses of vitamin A lead to accelerated resorption of trabecular and cortical bone because of increased osteoclastic activity. A raised alkaline phosphatase, increased urinary hydroxyproline concentrations, and hypercalciuria correlate with these findings (54). One study suggested that high dietary intake of retinol might be associated with osteoporosis (55). 

Camara NO, Matos AC, Rodrigues DA, Pereira AB, Pacheco-Silva A. Urinary retinol binding protein isa good marker of progressive cyclosporine nephrotoxicity after heart transplant. Transplant Proc 2001 33(3) 2129-2131. 

Salem MA, el-Habashy SA, Saeid OM, el-Tawil MM,Tawfik PH Urinary excretion of n-acetyl-beta-D-glucosaminidase and retinol binding protein as alternative indicators of nephropathy in patients with type 1 diabetes mellitus. Pediatr Diabetes. 2002 3 37-41. 

Roels et al. [63] and Buchet et al. [118] observed a slightly higher prevalence of elevated urinary excretion of albumin, transferrin, retinol binding protein and the tubular enzyme [l-galactosidase in chloralkali workers with a urinary excretion of mercury exceeding 50 pg/ g creatinine. 

Attempts to define threshold levels for effects have produced mixed results. A no-efifect level of 72 g Hg/g creatinine was determined for urinary excretion of albumin, 2-microglobulin, or retinol binding protein (Bernard et al. 1987). However, other studies have shown increases in urinary albumin at urinary mercury levels >50 g Hg/g creatinine (Buchet et al. 1980) and increases in urinary /V-acetyl-... 

Ayatse JOJ, Kwan JTC. Relative sensitivity of serum and urinary retinol binding protein and aj-microglobuhn in the assessment of renal function. Ann CUn Biochem 1991 28 514-6. 

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