FIG. 9.

Antagonistic effects of the synthetic retinoids CD2331 and CD2366 on RA-induced activation of TREpal-tk-CAT and inhibition of specific receptor subtypes. CV-1 cells were transiently transfected with 100 ng of TREpal-tk-CAT reporter together with RARα and RXRα expression plasmids (top panel), RARβ₂ and RXRα (middle panel), or RARγ₁ and RXRα (bottom panel). Transfected cells were treated with 10 nM RA, with the indicated concentrations of CD2366 and CD2331, or with the combination of RA and antagonists. CAT activity was assayed after 24 h as described in Materials and Methods. The activation obtained in the presence of 10 nM RA alone represents the maximum value. The data shown represent the means from two experiments carried out in duplicate, and the error bars represent standard deviations. The standard errors of the mean values were between 0.02 and 0.5.