In situ double-beam NADH laser fluorimetry: choice of a reference wavelength.

A double-beam laser fluorimeter, using a single optical fiber to guide the lights, was constructed for in situ and on-line monitoring of NADH concentration [( NADH]) from normally blood-perfused living tissues. The device was tested on an isolated blood-perfused rat heart system to determine the most efficient reference wavelength for the compensation of the hemodynamic artifact induced by blood circulation in the tissues on the fluorescence measure; 586 nm was found to be an accurate reference wavelength, and a mathematical relationship was established that allowed the digital treatment of the measured fluorescence to give a signal (compensated fluorescence) that varied only with [NADH] in the volume of tissue investigated.