抄録
In vivo oxygen measurement is the key to understanding how biological systems dynamically adapt to reductions in oxygen supply. High spatial resolution oxygen imaging is of particular importance because recent studies address the significance of within-tissue heterogeneities in oxygen concentration in health and disease. Here, I report a new technique for in vivo molecular imaging of oxygen in organs using green fluorescent protein (GFP). GFP expressing COS7 cells were briefly photo activated with a strong blue light while lowering the oxygen concentration from 10% to <0.001%. Red fluorescence (excitation 520–550 nm, emission >580 nm) appeared after a photo activation at <2% oxygen (the red shift of GFP fluorescence). The red shift disappeared after reoxygenation of the cell, indicating that the red shift is stable as long as the cell is hypoxic. The red shift of GFP fluorescence was also demonstrated in single cardiomyocytes isolated from the GFP knocked-in mouse (green mouse) heart. Then, we tried molecular imaging of hypoxia in in vivo organs. Using the macroscopic optics, the red shift could be imaged in the ischemic liver and kidney in the green mouse provided that oxygen diffusion from the atmospheric air was prevented. In crystalloid perfused beating heart isolated from the green mouse, significant spatial heterogeneities in the red shift were demonstrated in the epicardium distal to the coronary artery ligation. It was concluded that present technique using GFP as an oxygen indicator may allow molecular imaging of oxygen in in vivo organs. [J Physiol Sci. 2007;57 Suppl:S22]
