Table 1.

Typical level of radioactivity incorporated into adenine nucleotides in cultured rat cardiac fibroblasts

	ATP	ADP	AMP
5 mm glucose, 10 nm insulin	553 612	91 312	1477 215
5 mm glucose, no insulin	511 560	81 968	1344 382
25 mm glucose, 10 nm insulin	571 725	93 573	1525 668
25 mm glucose, no insulin	503 213	79 901	1401 032

The data show counts min⁻¹ (mg cellular protein)⁻¹. Cells cultured in Dulbecco's modified Eagle's medium containing indicated concentrations of glucose and insulin (no insulin refers to a concentration of 10⁻¹¹m) were labelled with [8-¹⁴C]adenine as described in the Methods. The cells were extracted with perchloric acid, and acid-soluble radiolabelled purine nucleotides were separated by thin-layer chromatography, located under UV, and the radioactivity was counted in a β-counter. In consecutive experiments, the radioactivity ratio between these nucleotides varied by 10–20%.