AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 4 982-R988, Copyright © 1989 by American Physiological Society
Capillary and mitochondrial unit in muscles of a large lizard
K. E. Conley, K. A. Christian, H. Hoppeler and E. R. Weibel
Department of Anatomy, University of Berne, Switzerland.
We asked whether capillaries and mitochondria form a structural and
functional unit in the musculature of the Cuban iguana (Cyclura nubila)
similar to that found in mammals. We found a significant correlation
between capillary length density [Jv(c, f)] and mitochondrial volume
density [Vv(mt, f)] of the musculature with a slope that revealed that on
average 3.5 km of capillaries were associated with each milliliter of
mitochondria (vs. approximately 11 km/ml in mammals). These capillaries had
a diameter of 9 microns (vs. 4.5 microns in mammals), and the mitochondria
had a surface density of the inner membranes of 25 m2/ml (vs. 30-45 m2/ml
in mammals). These dimensions resulted in ratios of capillary to
mitochondrial volume (0.22 ml/ml) and capillary wall to mitochondrial
membrane surface area (39 cm2/m2) that were similar in Cyclura to those
found in mammals (approximately 0.18 ml/ml and 35-52 cm2/m2, respectively).
Also in agreement with mammalian values were the average oxidative capacity
of the mitochondria derived from maximum rate of O2 consumption (VO2max)
during exercise at 37 degrees C and the inner mitochondrial membrane
surface area [S(im)] of the musculature [VO2max/S(im) = 0.04 vs. 0.06-0.15
ml O2.m-2.min-1 in mammals]. These common structural and functional
relationships support the notion that capillaries and mitochondria
represent a similar fundamental unit in muscles of both Cyclura and
mammals.
