Cloning of the rat α(1C)-adrenergic receptor from cardiac myocytes: α(1C), α(1B), and α(1D) mRNAs are present in cardiac myocytes but not in cardiac fibroblasts

A. F.R. Stewart, D. G. Rokosh, B. A. Bailey, L. R. Karns, K. C. Chang, C. S. Long, K. I. Kariya, P. C. Simpson

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93 Scopus citations

Abstract

α1-Adrenergic receptor (AR) activation in cardiac muscle has several different physiological effects that might be mediated through different α1-AR subtypes. Two α1-AR subtypes have been cloned from the rat, the α(1B) and the α(1D); both are present in adult rat heart. A third subtype, the α(1C), cloned from the cow and human, was reported to be absent in the rat. However, we recently found α(1C) mRNA in adult rat heart by using a partial α(1C) cDNA. Thus, all three cloned α1-AR subtypes are present in the heart, but it is unknown whether each is expressed in cardiac myocytes or in cardiac fibroblasts. In the present study, the full-length rat α(1C)-AR was cloned from cultured neonatal cardiac myocytes. α(1C) mRNA transcripts of 3, 9.5, and 11 kb were present in adult rat heart by Northern blot analysis, α(1B)-, α(1C)-, and α(1D)-subtype mRNAs were each present in isolated adult and neonatal cardiac myocytes by RNase protection assay. In addition, cultured neonatal cardiac myocytes expressed the three α1-AR subtype mRNAs. In contrast, none of the α1-AR mRNAs was detected in cultured neonatal cardiac fibroblasts. In addition, α1-ARs were absent in fibroblasts by [3H]prazosin binding and norepinephrine-stimulated [3H]inositol phosphate production. The absence of α1-ARs in cardiac fibroblasts differs from β-adrenergic and angiotensin II receptors, which are present in both cardiac fibroblasts and cardiac myocytes. Three α1-AR subtypes in cardiac myocytes will need to be considered in future studies of the physiological effects of α1-AR activation in cardiac muscle.

Original languageEnglish
Pages (from-to)796-802
Number of pages7
JournalCirculation research
Volume75
Issue number4
DOIs
StatePublished - 1994

Keywords

  • cardiac fibroblasts
  • cardiac myocytes
  • α-adrenergic receptors

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