Maintenance of heterogeneity of capillary spacing is essential for adequate oxygenation in the soleus muscle of the growing rat.
OBJECTIVE
Normal muscle growth is accompanied by capillary proliferation, which usually lags behind the increase in muscle size, causing a decline in mean capillary density (CD). It is not known, however, how the capillary distribution is affected and what impact it has on the oxygenation of the muscle.


METHODS
The capillarization of soleus muscles of rats (64-425 g) was determined with the method of capillary domains. As well as quantifying CD, capillary to fiber ratio (C:F), and fiber size, this method provides a measure of the heterogeneity of capillary spacing. Capillary locations were used to mathematically model oxygenation levels within the muscle.


RESULTS
The increase in muscle mass was largely attributable to 5-fold increase in fiber size, accompanied by a more than 3-fold rise in C:F. The mismatch between rates of angiogenesis and muscle growth resulted in a decrease in CD. However, the heterogeneity of capillary spacing was unaffected (heterogeneity index logRSD: 0.091 +/- 0.013; mean +/- SD) as was muscle PO2, with modal values between 4 and 60 mmHg (0.5 and 8 kPa).


CONCLUSIONS
Angiogenesis during normal muscle growth does not maintain CD, but with similar heterogeneity of capillary spacing it preserves the potential for adequate intramuscular oxygenation.
Degens
Hans
H
Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Alsager Campus, Alsager, Cheshire, UK. h.degens@mmu.ac.uk
Deveci
Durmus
D
Botto-van Bemden
Angie
A
Hoofd
Louis J C
LJ
Egginton
Stuart
S
D000818:Animals; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008955:Models, Cardiovascular; D024510:Muscle Development / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000254:growth & development* / Q000378:metabolism; D018919:Neovascularization, Physiologic; D010101:Oxygen Consumption / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar