A METHOD FOR MEASURING THE RATE OF OXYGEN RELEASE FROM SINGLE MICROVESSELS

A system determining the rate of oxygen release from erythrocytes flow ing in single microvessels was constructed with an inverted microscope by connecting 1) a scanning/grating spectrophotometer equipped with a photon-counting detector through a thin light guide, to obtain the vi sible absorption spectrum of a spot (5-mu-m in diameter) focused on a microvessel, 2) two photomultipliers (connected to a microcomputer via an analog-to-digital converter) through two light guides, to determin e the flow velocity of erythrocytes by calculating the cross correlati on between the light-intensity changes of two spots (3-mu-m in diamete r, 5-mu-m apart from each other) focused on the microvessel, and 3) an image processor through a video camera, to estimate the diameter of m icrovessel from the digitized video images. The rate of oxygen release from single microvessels 7-25-mu-m in diameter in rat mesentery was m easured under the superfusion of deoxygenated solution: 1) The maximal rate was obtained in capillaries, and the rate in arterial microvesse ls was larger than that in venous microvessels, when similar diameters were compared. 2) The rate was maximum at pH 7.0-7.2, and it decrease d in more acidic and alkaline pH values. 3) The rate decreased with a decrease in temperature. The reliability of the measurement using the present apparatus was tested in detail.