AJP - Heart and Circulatory Physiology, Vol 246, Issue 6 739-H746, Copyright © 1984 by American Physiological Society
Structural compensatory mechanisms in rat heart in early spontaneous hypertension
P. Anversa, M. Melissari, C. Beghi and G. Olivetti
The response of the left ventricle (LV) during the development of
spontaneous hypertension (SH) in rats was studied morphometrically at 21,
28, 35, and 45 days after birth and compared with that of normotensive (WK)
controls. LV hypertrophy, varying from 24 to 27%, was characterized by the
preservation of the volume fraction of capillary lumen and capillary
luminal surface in the myocardium, as a result of capillary proliferation.
From 21 to 45 days the number of capillaries per unit area of myocardium
increased 68% in SH rats by the insertion in parallel of new capillary
elements among the myocytes. This estimation was obtained by correcting the
value of capillary density at 45 days for the amount of spreading produced
by myocyte growth during this interval. On a similar basis capillary
proliferation was only 24% in WK rats. Myocyte growth in experimental
animals (151%) was achieved by a 77% enlargement in myocyte cross-sectional
area (MCSA) and by a 42% lengthening of the cells. In controls myocyte
expansion (124%) was the result of comparable increments in MCSA (47%) and
myocyte length (53%).
