Distribution of endogenous retinoids, retinoid binding proteins (RBP, CRABPI) and nuclear retinoid X receptor ? (RXR?) in the porcine embryo

Abstract

-Retinoids are important signalling molecules in the development of limbs and in the determination of the anterior-posterior orientation of the embryo. The present study examined the content and distribution of retinoic acid, retinol and retinyl esters in porcine embryos during early gestation (gestation days 22-30) macroscopically and microscopically by its autofluorescence and by HPLC. Macroscopically, the yellowish-greenish autofluorescence characteristic of vitamin A was observed in tissues affected by morphogenesis, such as the limbs, in a spatial and temporal manner. Changes in the intensity of autofluorescence in the limbs paralleled changes in the concentration of retinoids in these structures. In the limbs and the body, retinol, retinyl palmitate, and all-trans-retinoic acid but neither the isomers of all-trans retinoic acid nor other retinoid metabolites were detected. In addition, the distribution of specific retinoid-binding proteins was investigated; these are involved in vitamin A transport, metabolism and signal transduction. Immunoreactive retinol-binding protein as well as cellular retinoic acid binding protein type I were only localised in the mesonephros, while the retinoid X receptor b was widely distributed in most of the tissues and organs of the embryo throughout the time period investigated. The combination of autofluorescence and HPLC analysis allowed for the first time to attribute the yellowish-greenish autofluorescence in specific regions of the embryo to vitamin A, and offers a method to study the local cellular distribution of retinol and/or retinyl esters as well as their concentrations in embryonic tissues. retinoid / vitamin A / binding protein / nuclear receptor / autofluorescence / embryo / pig Reprod. Nutr. Dev. 42 (2002) 285-294 285

An Endogenous Mammalian Retinoid X Receptor Ligand, At Last!

“…[23b] Similarly,L C analysiso fp orcinee mbryos during early gestation didn ot detect anyo ft he isomersof2c. [32] Studies in humans led to similar results. Both 2c and its 13cis isomer 4c were characterized ase ndogenousr etinoids in the serum of fastingv olunteers by normal-and reversed-phase LC, with UV detection, and by comparison with standards, at ac oncentration of approximately 4.7nm (1.4 ng mL À1 ).…”

“…The same ultrasensitive technique was unable to identify 9‐ cis ‐retinoic acid ( 1 c ) in any region of the spinal cord unless teratogenic doses of all‐ trans ‐retinoic acid ( 2 c ) were administered to feeding pregnant mice . Similarly, LC analysis of porcine embryos during early gestation did not detect any of the isomers of 2 c …”

Methods for detecting and identifying retinoids in tissue

“…yellowish-greenish autofluorescence has been used to macroscopically localize retinol and/or retinyl esters in specific regions of the porcine embryo (Schweigert et al, 2002).…”

Bovine Early Embryonic Development and Vitamin A

“…These levels are functionally active, and a higher ROH contents in the TE is consistent with tissues undergoing active differentiation (Schweigert et al 2002). Endogenous retinoids in the embryonic cells can derive from the culture environment, the originating oocyte or both.…”

“…1998). These levels are functionally active, and a higher ROH contents in the TE is consistent with tissues undergoing active differentiation (Schweigert et al. 2002).…”