Degeneration release of noradrenaline in skin flaps in rats

To study if noradrenaline released from degenerating sympathetic nerves may contribute to metabolic stimulation and low blood flow in an experimental skin flap, we have determined noradrenaline levels in such skin flaps. Attempts to use radioenzymatic methodology for the determination of noradrenaline in rat skin extracts were unsuccessful due to interference with the assay. High performance liquid chromatography with electrochemical detection was, however, found to give accurate estimates of rat skin noradrenaline contents. Rat skin contained approximately 2.7 nmol (455 ng) noradrenaline per gram dry weight. Extensive depletion of skin flap noradrenaline, occurring mainly between 6 and 24 h postoperatively, was found. At 48 h nearly all sympathetic nerves in the skin flaps had degenerated as evidenced by noradrenaline levels of 0.13 nmol/g. The degeneration of sympathetic nerve endings appears to proceed from the sides towards the middle of the flap, indicating a segmental distribution of the nerves. Noradrenaline released from degenerating sympathetic nerves may adversely affect the survival of critical skin flaps by causing vasoconstriction and metabolic stimulation.