Gender differences in biomechanical properties of intramural coronary resistance arteries of rats, an in vitro microarteriographic study

Abstract

The prevalence of ischemic heart disease is lower in premenopausal females than in males of corresponding age. This should be related to gender differences in coronary functions. We tested whether biomechanical differences exist between intramural coronary resistance arteries of male and female rats. Intramural branches of the left anterior descending coronary artery (uniformly ∼200 μm in diameter) were isolated, cannulated and studied by microarteriography. Intraluminal pressure was increased from 2 to 90 mmHg in steps and steady-state diameters were measured. Measurements were repeated in the presence of vasoconstrictor U46619 (10 −6 M) and the endothelial coronary vasodilator bradykinin (BK) (10 −6 M). Finally, passive diameters were recorded in calcium-free saline. A similar inner radius and a higher wall thickness (41.5±2.9 μm vs. 31.4±2.7 μm at 50 mmHg in the passive condition, p < 0.05 ) resulted in lower tangential wall stresses in male rats (18.9±1.9 kPa vs. 24.9±2.5 kPa at 50 mmHg, p < 0.05 ). Isobaric elastic modulus of vessels from male animals was significantly smaller at higher pressures. Vasoconstrictor response was significantly stronger in male than in female animals. Endothelial relaxations induced by BK were not different. This is the first demonstration that biomechanical characteristics of intramural coronary resistance arteries of a mammalian species are different in the male and female sexes. Higher wall thickness and higher vascular contractility in males are associated with similar endothelial function and larger high-pressure elasticity compared to females. These gender differences in biomechanics of coronary resistance arteries of rats may contribute to our better understanding the characteristic physiological and pathological differences in humans.