Developmental changes in regulation of mitochondrial respiration by ADP and creatine in rat heart in vivo.
In saponin-skinned muscle fibers from adult rat heart and m. soleus the apparent affinity of the mitochondrial oxidative phosphorylation system for ADP (Km = 200-400 microM) is much lower than in isolated mitochondria (Km = 10-20 microM). This suggests a limited permeability of the outer mitochondrial membrane (OMM) to adenine nucleotides in slow-twitch muscle cells. We have studied the postnatal changes in the affinity of mitochondrial respiration for ADP, in relation to morphological alterations and expression of mitochondrial creatine kinase (mi-CK) in rat heart in vivo. Analysis of respiration of skinned fibers revealed a gradual decrease in the apparent affinity of mitochondria to ADP throughout 6 weeks post partum that indicates the development of mechanism which increasingly limits the access of ADP to mitochondria. The expression of mi-CK started between the 1st and 2nd weeks and reached the adult levels after 6 weeks. This process was associated with increases in creatine-activated respiration and affinity of oxidative phosphorylation to ADP thus reflecting the progressive coupling of mi-CK to adenine nucleotide translocase. Laser confocal microscopy revealed significant changes in rearrangement of mitochondria in cardiac cells: while the mitochondria of variable shape and size appeared to be random-clustered in the cardiomyocytes of 1 day old rat, they formed a fine network between the myofibrils by the age of 3 weeks. These results allow to conclude that in early period of development, i.e. within 2-3 weeks, the diffusion of ADP to mitochondria becomes progressively restricted, that appears to be related to significant structural rearrangements such as formation of the mitochondrial network. Later (after 3 weeks) the control shifts to mi-CK, which by coupling to adenine nucleotide translocase, allows to maximally activate the processes of oxidative phosphorylation despite limited access of ADP through the OMM.
Tiivel
T
T
Laboratory of Bioenergetics, Institute of Chemical and Biological Physics, Tallinn, Estonia.
Kadaya
L
L
Kuznetsov
A
A
Käämbre
T
T
Peet
N
N
Sikk
P
P
Braun
U
U
Ventura-Clapier
R
R
Saks
V
V
Seppet
E K
EK
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D019069:Cell Respiration; D003401:Creatine / Q000378:metabolism*; D003402:Creatine Kinase / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005456:Fluorescent Dyes; D006321:Heart / Q000187:drug effects / Q000254:growth & development*; D007700:Kinetics; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000378:metabolism; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009929:Organ Size; D010085:Oxidative Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D014357:Trypsin / Q000494:pharmacology
D005456:Fluorescent Dyes; D000244:Adenosine Diphosphate; D000226:Mitochondrial ADP, ATP Translocases; D003402:Creatine Kinase; D014357:Trypsin; D003401:Creatine