Retinol-binding protein clinical studies

What defects in vitamin A transport or utilization are likely to occur in the diseased eye The cytosol and IPM binding proteins and their possible receptors are clearly essential components of the visual system, as are the specific enzymes that are implicated at certain stages of the visual cycle (Table II). Failure to isomerize el -trans to Il-cu-retinoid is one obvious possibility, and a clinical trial was carried out by Chatzinoff et al. (1968) in an attempt to answer this question. The compound ll-c/5- vitamin A (the retinoid used was not reported) was injected intramuscularly into retinitis pigmentosa patients over a 3-year period. This group was then compared with a parallel group of patients that had received the all-trans isomer. No beneficial effect of 11-crr-retinoid was found. However, the ease with which the 11-cis isomer isomerizes back to all-trans when dispersed in tissue preparations (see Section III,G,4,b) casts doubt on the likelihood that in this study any 11-cM-retinol would have survived to be delivered to the RPE. 

The retinol transport system provides an interesting model for the study of protein-protein and protein-retinoid interactions and of the characteristics and metabolic regulation of a specific binding and transport system. The aim of this chapter is to summarize the information available about this transport system, including information about the structure and chemistry, biochemistry, and metabolism of RBP, and about related clinical phenomena. Brief comments are also... 

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