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.
Laboratory of Bioenergetics, Institute of Chemical and Biological Physics, Tallinn, Estonia.
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T
Tiivel
L
L
Kadaya
A
A
Kuznetsov
T
T
Käämbre
N
N
Peet
P
P
Sikk
U
U
Braun
R
R
Ventura-Clapier
V
V
Saks
E K
EK
Seppet
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