Cyclic AMP and cyclic AMP-dependent protein kinase in mouse skin. II. In vitro effects of isotretinoin and etretinate.

Skin from hairless mice was incubated with two synthetic retinoids, isotretinoin and etretinate, and the cAMP content as well as the activity of cAMP-dependent protein kinase were determined. A crude plasma membrane preparation was used to measure adenylyl cyclase activity. Neither isotretinoin (10(-6) and 10(-5)M) nor etretinate (10(-6)-10(-4)M) produced any significant changes in adenylyl cyclase activity. Tissue cAMP levels also remained unaltered after treatment with these retinoids. Although the protein kinase activity ratios remained constant over the concentration range of each retinoid, absolute protein kinase activity was stimulated by treatment with etretinate. These data suggest that cAMP may not mediate the action of retinoids in skin, and that the stimulation of protein kinase activity caused by etretinate probably involves an alternative mechanism.