Phosphate metabolites in rat skin.

A model for studying the 31P NMR spectrum of rat skin without contribution from other tissue signals has been developed by creating a skin pedicle. 31P NMR spectra were obtained with a solenoidal coil, which was separated from the flank of the rat by a Faraday shield. Phosphomonoesters, inorganic phosphate (Pi) (1.63 +/- 0.12 mumols per g wet wt), phosphodiesters, phosphocreatine (PCr) (1.4 +/- 0.12 mumols per g wet wt) and ATP (1.35 +/- 0.22 mumols per g wet wt) were observed, superimposed on broader signals, probably due to phospholipids. Extracts of freeze-clamped pedicles contained concentrations of phosphorus metabolites similar to those seen by NMR. The exception was Pi which was twofold higher in the extract. The presence of the broader phospholipid contribution suggests that the signals did not arise solely from the panniculus carnosus muscle of rat skin, although this muscle was evident on histological examination of the pedicles. In extracts of normal rat skin levels of creatine, ATP, ADP and Pi were similar to those of pedicles, whereas PCr was about twofold higher. Signals from rat skin are likely to contribute to spectra of subcutaneous organs and tumours. Two kinds of rat hepatoma that contained no PCr frequently gave PCr signals from the overlying skin, whereas in three other subcutaneous tumours the contribution from skin was negligible.