Differences in Cardiac Hypertrophy in Exercise and in Hypoxia

Abstract

A group of rats, including both sexes, was exercised on an electrically-driven treadmill at the rate of one mile per hour for two hours daily to a total of 60 hours. Another group, also including both sexes, was exposed to intermittent hypoxia for eight hours daily, six days per week, for four weeks at a barometric pressure of 303 mm Hg corresponding to a simulated altitude of approximately 24,000 feet (7,315 m). All these animals showed significant hypertrophy of both ventricles. Exercise produced about the same percentage of weight increase in the right and also in the left ventricular walls. The per cent increase of the right ventricular wall relative to that of the left ventricular wall was greater after intermittent hypoxia than after exercise. The ratio of left ventricular weight/right ventricular weight was significantly less in the hypoxic group than in the exercised group. This indicates a relative right ventricular hypertrophy produced by the intermittent hypoxia. Reasons are given to indicate that the pulmonary hypertension associated with hypoxia is the cause of this right ventricular predominance.

Morphometry of exercise-induced right ventricular hypertrophy in the rat.

“…When the primary stimulus is volume overload, however, the elevation in diastolic wall stress should be relatively greater per unit volume of tissue in the right ventricle because of its smaller total number of myocytes, less ventricular mass, and thinner wall. In contrast with the present findings in Wistar Kyoto rats, an approximately similar amount of hypertrophic growth in the right and left ventricular myocardium has been shown in albino rats subjected to the same kind of physical conditioning (Van Liere et al, 1965). On the other hand, both female and male Sprague-Dawley rats on a more moderate treadmill running program did not develop hypertrophy of either ventricle (Dowell et al, 1976a(Dowell et al, , 1976b.…”

Bilateral Ventricular Hypertrophy in Rats Exposed to Acute or Chronic Hypobaric Hypoxia

“…Since this disagreement exists we would point out that many factors such as the sex, age, and health of the animals play a role in the genesis of hypoxia-in duced left ventricular hypertrophy. More over, in our experiments the rats under went a more severe and sustained degree of hypoxia than in previous studies [11,16,21,23]. Our data show a significant de gree of left ventricular hypertrophy in the posthypoxic rats.…”

“…However, a number of critical factors including increase in cardiac out put [21]: overload imposed to the left ven tricle by polycythemia [I]; deficiency of high energy phosphate [13] and/or circu lating factors [2,3] may account for the de velopment of the hypertrophic process in our experimental conditions.…”

Effects of exercise‐training on hypoxia and angiotensin II‐induced pulmonary vasoconstrictions

“…This study has shown that rats undergoing chronic running exercise-training develop increased left ventricular hypertrophy. Previous studies have shown that endurance exercisetraining increases the left ventricular wall thickness in rats (Liere et al 1965). Left ventricular hypertrophy can be explained by a marked increase in the systemic circulation during the exercise, i.e.…”