Fig. 4. Effect of forskolin on the expression of G1 cyclin, CDK and CKI proteins. Reh cells were treated with forskolin (100 µM) for the hours indicated. Total cell lysates (50 µg) from treated or untreated cells were subjected to immunoblot analysis, as described in Materials and Methods, using antibodies specific for (A) cyclins and CDKs and (B) CKI proteins. One representative immunoblot of three is shown.