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 Gi alpha 2, Go alpha, and the G beta-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, Gs alpha mRNA was more abundant than mRNA for Go alpha, Gi alpha, and G beta. In adipose tissue, mRNA levels were as follows: 19.4, 7.6, 7.0, and 2.3 amol mRNA per micrograms total cellular RNA for Gs alpha, G beta, Gi alpha 2, and Go alpha, respectively. In heart Gs alpha mRNA was less abundant than in adipose, but the relative trend among the G-protein subunits was the same. In liver, G beta mRNA was more abundant than either Go alpha or Gi alpha 2. Go alpha mRNA levels ranged from 1.2 to 2.3 amol/micrograms 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 Gi alpha 2, Gs alpha, Go alpha, and G beta-subunit mRNAs in several mammalian tissues.