Retinol-binding protein function

The other major class of extracellular LBPs of mammals is the lipocalins (Flower, 1996). These are approximately 20 kDa, P-sheet-rich proteins, performing functions such as the transport of retinol in plasma or milk, the capture of odorants in olfaction, invertebrate coloration, dispersal of pheromones, and solubilizing the lipids in tears (Flower, 1996). The retinol-binding protein (RBP) of human plasma is found in association with a larger protein, transthyretin, the complex being larger than the kidney threshold and thus not excreted, although the RBP itself may dissociate from the complex to interact with cell surface receptors in the delivery of retinol (Papiz et al., 1986 Sundaram et al., 1998). 

Godovac-Zimmermann, J., Conti, A., Liberatori, J., and Braunitzer, G. 1985. Homology between the primary structures of beta-lactoglobulins and human retinol-binding protein Evidence for a similar biological function Biol Chem Hoppe Seyler 366(4) 431-434. 

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). 

Estimation of the glomerular filtration rate (GFR) is considered a sensitive index of functional nephron mass (Newman and Price 1999). Point measurements of the plasma levels of several endogenous small molecules (urea, creatinine, 2-(a-mannopyranosyl)-L-tryptophan) or small (less than 66 kDa) proteins (cystatin C (y-trace), prostaglandin D synthase (15-trace protein), ai-microglobulin, p2-microglobulin, and retinol binding protein) have been used to assess GFR in many species. 

Pervaiz S, Brew K. Homology and structure-function correlations between tti-acid glycoprotein and serum retinol-binding protein and its relatives. FASEB J 1987 1 209-14. 

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. 

Napoli JL. A gene knockout corroborates the integral function of cellular retinol-binding protein in retmoid metabolism. Nutr Rev 2000 58 230-6. 

Tubular function p-Ami noh ippu rate N- -Methyinicotinamide (NMN) Tetraethylammonium (TEA) /J2-Microglobulin Retinol-binding protein (RBP) Protein HC (ai-microglobulin) N-Acetylglucosaminidase (NAG) Alanine aminopeptidase (AAP) Adenosine binding protein (ABP)... 

LBM includes skeletal muscle, somatic protein, and functional proteins such as circulating proteins and the visceral proteins. Biochemically, LBM can be assessed by measuring the serum visceral proteins, albumin (ALB), transferrin (TFN), and prealbumin (thyroxine-binding prealbumin or transthyretin). Other serum proteins, such as retinol-binding protein, flbronectin (an opsonic protein), and somatomedin-C (insulin-like growth factor-1), that have a very short half-life (less than 12 to 24 hours), have been suggested as... 

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