The presence of CRBP in those cells also expressing CRABP(II) is consistent with its role in the production of retinoic acid. CRBP was also present in the smooth muscle cell layers that expressed CRABP. There its role is less clear. Smooth muscle cells from the uterus of the pseudopregnant rat were found not to synthesize retinoic acid. It is generally accepted that CRBP also mediates retinol esterification as well as production of retinoic acid. We have observed that the smooth muscle of the small intestine possesses large stores of retinol esters and that it contains both CRBP and the enzyme activity responsible for the esterification of retinol, lecithin-retinol acyltransferase, suggesting that the muscle may serve as a local store of vitamin A. buy diabetes drugs

We have recovered significant retinol ester in extracts of total uterus (unpublished results). The muscle cell may serve a similar role as a site of storage of retinol in the uterus, since the uterus appears to carry out extensive retinoid processing. The mechanism for mobilization of the esters to produce retinol or active retinoids has not been elaborated, although the smooth muscle of the intestine does contain a potent retinol ester hydrolase activity.