FIG. 4.

(A) Multiple-tissue Northern blot hybridized to a β3-specific exon B probe. A 7.0-kb mRNA is predominant in the kidneys, liver and lungs, expressed at lower levels in the skeletal muscle, spleen, brain, and heart, and absent from the testes. An additional 4.0-kb mRNA is restricted to skeletal muscle. (B) The same blot hybridized to a Δβ3 probe at high stringency. A 7.0-kb mRNA predominates in the lungs and spleen and is present at low levels in the brain. A 3.0-kb mRNA is present in the same tissues, and a 1.5-kb transcript is evident in the spleen. (C) The same blot hybridized to a β-actin cDNA to show that similar amounts of intact RNA are loaded in each lane. (D) Multiple-tissue Northern blot hybridized to a β1-specific probe. A 6.2-kb mRNA is predominant in the kidneys, liver, brain, and heart, expressed at lower levels in the skeletal muscle, just detectable in the lungs and spleen, and absent from the testes. (E) The same blot hybridized to β2- and α1/α2-specific probes. A 6.2-kb β2 mRNA is clearly expressed in the brain and is just detectable in the lungs and heart but absent from other tissues. The 5.5- and 2.6-kb TRα1 and TRα2 transcripts were expressed at the highest levels in the brain and at lower levels in the kidneys, skeletal muscle, lungs, and heart, were barely detectable in the testes and liver, and were absent from the spleen. (F) Same blot as in panels D and E hybridized to a β-actin cDNA.