Cycloheximide induces the alpha 1B adrenergic receptor gene by activation of transcription in DDT1 MF-2 smooth muscle cells.

alpha 1-Adrenergic receptors play important roles in mediating a wide range of important cellular responses; regulation of expression of these receptors may have pathophysiological significance in diseases such as hypertension. In order to pursue understanding of mechanisms involved in the regulation of expression of alpha 1 receptors, the effects of protein synthesis inhibitor cycloheximide on alpha 1B receptor gene expression were examined in DDT1 MF-2 smooth muscle cells. Cycloheximide markedly induced accumulation of the alpha 1B receptor mRNAs in a concentration- and time-dependent manner as detected by Northern blotting assays. The increased accumulation of alpha 1B receptor mRNA could be detected at 1 hr (1.7 +/- 0.2-fold) and the maximal accumulation occurred at 6 hr (5.4 +/- 0.3-fold, p < 0.01). Nuclear runoff assays reveal that cycloheximide markedly increased the transcriptional rate of the alpha 1B receptor gene. The stability of alpha 1B receptor mRNAs measured by RNase protection assays was essentially unchanged by cycloheximide. Incubation of DDT1 MF-2 cells with two additional protein synthesis inhibitors, anisomycin and emetine, had similar effects to those of cycloheximide. However, a further inhibitor, puromycin, did not induce alpha 1B receptor mRNAs when protein synthesis was almost completely inhibited. Furthermore, puromycin did not inhibit the capacity of cycloheximide to induce transcription of the alpha 1B receptor gene. These observations suggest that cycloheximide induces alpha 1B receptor gene expression through direct activation of gene transcription rather than inhibition of protein synthesis.