Please click here to obtain permission to reproduce this image.
Click on image to view larger version.
Figure 1 Examples of the Michaelis-Menten kinetics of the oxygen consumption of permeabilized vastus lateralis myofibers to increasing levels of the phosphate acceptor adenosine diphosphate (ADP). (A) Raw data obtained by myofibers respiration within the oxygraphic chamber from a representative patient with chronic heart failure (CHF) (upper) and an active control (lower). The tissue O2 consumption (V, µmoles O2·min–1·g–1 dry weight) increases with increasing doses of the phosphate acceptor ADP. These experiments were performed in the absence (thick line) or in the presence (thin line) of 20 mM creatine. Panel B shows the ADP-related respiration characterizing the Michaelis and Menten kinetics of ADP phosphorylation for the same CHF (interrupted lines) or active normal controls (ACT) (continuous line) groups as in panel A. The upper part represents the experiments without creatine and the lower part those with 20 mM creatine. The striking difference in maximal tissue oxygen uptake between the patients with CHF and the active control group is reflected by the differing asymptotic values of O2 uptake. In CHF, the fast increase in oxygen uptake with ADP reflects the low Km without creatine (42 µM), which is unchanged with creatine (25 µM). In the active control, the Km is much higher (214 µM) and decreases with creatine (59 µM).
|
