DISTRIBUTION OF ALPHA-1C-ADRENERGIC RECEPTOR MESSENGER-RNA IN ADULT-RAT TISSUES BY RNASE PROTECTION ASSAY AND COMPARISON WITH ALPHA-1B AND ALPHA-1D

Two al-adrenergic receptor (AR) subtypes have been defined by pharmaco logical studies in rat tissues, the alpha 1A and the alpha 1B, whereas three alpha 1-ARs have been cloned, alpha 1B, alpha 1C, and alpha 1D. It has been reported that alpha 1C mRNA is absent in all rat tissues, making uncertain the correspondence of this cloned subtype, if any, t o the native alpha 1-ARs defined by pharmacological criteria. In the p resent study, a partial alpha 1C-AR cDNA was obtained from rat cardiac myocytes using RT-PCR with degenerate primers. A sensitive RNase prot ection assay was used to map the distribution of alpha 1C mRNA in adul t rat tissues, in comparison with alpha 1B and alpha 1D. alpha 1C mRNA was abundant in heart, brain, aorta, vena cava, vas deferens, submaxi llary gland, lung, and kidney; was detected at lower levels in prostat e, parotid gland, and skeletal muscle; and was undetectable in liver a nd spleen, alpha 1B and alpha 1D mRNAs were present in most of the sam e tissues. In contrast to alpha 1C, however, alpha 1B and alpha 1D wer e both present in spleen; alpha 1B was the sole al-AR mRNA in liver; a nd alpha 1D mRNA was not detected in submaxillary gland, a tissue know n to be enriched in the pharmacological alpha 1A. We conclude that the distribution of alpha 1C-AR mRNA in rat tissues is compatible with th e idea that the alpha 1C corresponds to the classical native alpha 1A- AR. Although many tissues contain all three al-AR mRNAs, distinct tiss ue-specific expression is evident. (C) 1994 Academic Press, Inc.