The capillarity of the subendocardium of left ventricle in rats reared at a low temperature for many generations.
The cardiac capillarity in adult rats reared at 5 degrees C for 68 generations was studied with a double staining method of alkaline phosphatase and dipeptidylpeptidase IV. Capillary density, proportions of arteriolar, intermediate and venular capillary portions and capillary domain area were measured in the left ventricular wall. Compared with the control rats which had been brought back from the low temperature at the 12th generation and reared at 25 degrees C since then, the heart and the cardiac cells were hypertrophied, total capillary density increased and the capillary domain areas were reduced along the capillary path from the arteriolar to venular capillary portions. The number of the venular capillary portions showed no significant change but the arteriolar and intermediate capillary portions significantly increased. All these changes suggest that the cardiac capillary network was better developed in the cold-reared rats than in control rats. In the cold-adapted rats the hypertrophic changes in cardiac cells are thus accompanied by improvements in the oxygen delivery capacity. This adaptation provides a basis for the maintenance of increased thermogenesis in many organs. The changes cannot be established by several weeks exposure to low temperature, but only after rats have been bred in a cold room for generations.
Gao
M
M
Physiology Section, Hokkaido University, Sapporo, Japan.
Batra
S
S
Koyama
T
T
Yahata
T
T
Kuroshima
A
A
D000222:Adaptation, Physiological; D000818:Animals; D001160:Arterioles / Q000033:anatomy & histology; D001835:Body Weight; D002196:Capillaries / Q000033:anatomy & histology*; D003080:Cold Temperature; D004699:Endocardium / Q000033:anatomy & histology*; D006352:Heart Ventricles / Q000033:anatomy & histology; D008297:Male; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D014699:Venules / Q000033:anatomy & histology