Digital Imaging of The Oxygenation State within an Isolated Single Rat Cardiomyocyte

Abstract

Oxygen molecules released from erythrocytes in the capillary blood traverse plasma, capillary wall, extracellular fluid, cell membrane, cytosol, and mitochondrial membrane, and finally reach the mitochondrial inner membrane where they are utilized for ATP production. This process mainly depends on passive diffusion of the molecule along the oxygen pressure gradient between capillary blood and mitochondria. Therefore, the oxygen pressure at the mitochondrial inner membrane, P _i , can be represented by Eq.1

$$\mathop P\nolimits_i = \mathop P\nolimits_o - RV$$

(1)

where P _o is the capillary blood Po₂ while V and R are the oxygen flux (oxygen consumption rate) and the lumped diffusion resistance for oxygen, respectively. Above equation indicates the possibility that mitochondrial oxidative phosphorylation might be limited in the case that either capillary blood Po₂ is lowered or oxygen consumption is increased. However, at least physiologically, it may sound unlikely that this diffusion resistance critically limits oxidative ATP production, since the Km of isolated cytochrome c oxidase for oxygen is considerably low (i.e. less than 0.1 Torr) compared to the capillary blood Po₂ (usually well above 20 Torr).