retinoic acid ( ra ) , a naturally occurring metabolite of vitamin a , increased the number of receptors for nerve growth factor ( ngf ) in cultured human neuroblastoma cells ( la-n-1 ) , as indicated by an immunofluorescence assay of cell surface receptors and by specific binding of 125i-ngf to solubilized receptors .
C0040845
retinoic acid
C0042839
vitamin a