Myocardial capillaries in guinea pigs native to high altitude (Junin, Peru, 4,105 m).

Quantitative evaluation of the myocardial left ventricular capillarity was performed in three groups of guinea pigs: a) animals native to high altitude collected in Andean mountains, b) animals born at sea level and subjected to a stimulated high altitude postnatally, c) animals born and kept at sea level. The number of capillaries and muscle fibers/mm(2) as well as the fiber capillary ratio and the diffusion distance were similar in all three experimental groups. The only difference found during the detailed analysis of the myocardial capillarity was a slightly lower percentage of the myocardial tissue in the extreme distance from the capillary found in the hearts of high altitude natives when compared to sea level animals. From these morphometric data the distribution of diffusion distances was derived which can be approximated by lognormal distribution. Capillary inhomogeneity expressed as log standard deviation was found to be similar in all three groups.