Adenosine 3',5'-monophosphate effects on cartilage ribonucleic acid synthesis

We have previously shown that N6-monobutyryl-cAMP stimulates the incorporation of radiolabeled precursors into the macromolecules of embryonic chicken cartilage incubated in organ culture. The present study assessed the specific effects of N6-monobutyryl-cAMP on RNA synthesis in the cartilage organ culture system. The data show that treatment of cartilage with N6-monobutyryl-cAMP results in a coordinated stimulation of mRNA, rTNA, and tRNA synthesis. Incubation of cartilage with N6-monobutyryl-cAMP causes an increase of [5-3H]uridine incorporation into poly A-containing cartilage RNA and 28S, 18S, and 4S RNA as well. Increased incorporation of the radiolabeled nucleotide occurs without a measurable change in uridine triphosphate specific activity or in the rate of RNA degradation. Further, the isolated poly A-containing RNA directs protein synthesis in an in vitro cell-free system, and stimulation of cartilage mRNA by N6-monobutyryl-cAMP does not alter the size distribution of the mRNA species synthesized from that present in control tissue. These data indicate that cAMP enhances cartilage transcriptional activity. In addition, the increased synthesis of mRNA occurs antecedent to demonstrable effects on protein synthesis. Thus, the effects of cAMP on protein synthesis may be secondary to action at the nucleus.