- Regulation of Vitamin D hydroxylases gene expression by 1,25-dihydroxyvitamin D(3) and cyclic AMP in cultured human syncytiotrophoblasts. Avila, E., D??az, L., Barrera, D., Halhali, A., M??ndez, I., Gonz??lez, L., Zuegel, U., Steinmeyer, A., Larrea, F. J. Steroid Biochem. Mol. Biol. (2007)