ISSN:
1432-2013
Keywords:
Mitochondrial Respiration Rate
;
$$P_{{\text{O}}_{\text{2}} }$$ Electrode
;
Critical Oxygen Tension
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The respiration of cells and mitochondria of different rat tissues and of ascites tumor cells was measured with a polarographic method. The rate of respiration (μl O2/mg mitochondria protein×min) was controlled by the substrate, by the addition of ADP and by the temperature (25° and 37°C). By means of a membrane-covered platinum electrode no correlation was found between the rate of respiration and the $$P_{{\text{O}}_{\text{2}} }$$ below of which the rate of oxygen consumption decreases. Under optimum conditions especially at saturating concentrations of ADP and substrate, the rate of respiration (measured between ∼120 and 0 Torr $$P_{{\text{O}}_{\text{2}} }$$ ) is not sufficiently constant to allow the definition of a “critical $$P_{{\text{O}}_{\text{2}} }$$ ” as the $$P_{{\text{O}}_{\text{2}} }$$ measured polarographically, at which the rate of respiration drops to 90% of the maximum rate. Due to the variations in the $$P_{{\text{O}}_{\text{2}} }$$ measurements the above “critical $$P_{{\text{O}}_{\text{2}} }$$ ” becomes strongly dependent on the method of computation used to fit the $$P_{{\text{O}}_{\text{2}} }$$ values measured to a straight line and to measure the rate of respiration from it. An additional difficulty is induced by the response time of the electrode which causes the $$P_{{\text{O}}_{\text{2}} }$$ measured to follow the real $$P_{{\text{O}}_{\text{2}} }$$ with a time lag large enough to significantly influence the measurements of the “critical $$P_{{\text{O}}_{\text{2}} }$$ ”. Because of these difficulties, the so measured “critical $$P_{{\text{O}}_{\text{2}} }$$ ” is not a function of the respiratory properties of cells and mitochondria but depends largely on the measuring device.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00587868
Permalink
