G-protein subunit mRNA levels in rat heart, liver, and adipose tissues: Analysis by DNA-excess solution hybridization

The steady-state levels of mRNAs for the G-proteins G_iα2, G_oα, and the G_β-subunits common to each were established in rat adipose, heart and liver. Uniformly-radiolabeled, single-stranded antisense probes were constructed from cDNAs or assembled from oligonucleotides. Direct comparison of the steady-state levels of the G-protein mRNAs was performed under identical assay conditions, and on a molar basis. In adipose, liver and heart, G_sα mRNA was more abundant than mRNA for G_oα, G_iα, and G_β. In adipose tissue, mRNA levels were as follows: 19.4, 7.6, 7.0, and 2.3 amol mRNA per μg total cellular RNA for G_sα, G_β, G_iα2, and G_oα, respectively. In heart G_sα mRNA was less abundant than in adipose, but the relative trend among the G-protein subunits was the same. In liver, G_β mRNA was more abundant than either G_oα or G_iα2. G_oα mRNA levels ranged from 1.2 to 2.3 amol/μg total RNA in liver and adipose, respectively. The present work demonstrates the many advantages of this strategy when applied to the study of a family of homologous, low-abundance proteins and establishes for the first time the molar levels of G_iα2, G_sα, G_oα, and G_β-subunit mRNAs in several mammalian tissues.