Differential biomechanics in resistance arteries of male compared with female Dahl hypertensive rats

BACKGROUND: Increase in vascular stiffness is associated with a higher risk of cardiovascular morbidity and mortality and is likely sex-specific. METHOD: Our objectives were to compare structural and functional alterations in small resistance arteries as related to vascular stiffness from Dahl salt-sensitive male and female rats (n = 8, mean ± s.e.m.). RESULTS: Arterial blood pressure and pulse wave velocity were significantly (P < 0.05) elevated in males (161 ± 3 mmHg; 6.4 ± 0.2 m/s) and females (147 ± 2 mmHg; 5.5 ± 0.1 m/s) on a high (H) salt compared with regular (R) diets but were significantly higher in males (H) than in all others. Significant increases in collagen and smooth muscle cell areas were evident in ultrastructure of mesenteric arteries of hypertensive males compared to normotensive or corresponding females. There were no significant differences in composite Young's modulus (CYM) between groups. Vasoconstriction resulted in significantly higher CYM in male (H: 8.6 ± 1 KPa) than R (4.5 ± 0.8 KPa), and the corresponding females (H: 5.6 ± 0.6 KPa and R: 5 ± 0.9 KPa). In contrast, vasodilation significantly reduced CYM in the male groups (H: 2.5 ± 0.4 KPa and R: 2.7 ± 0.5 KPa) compared with the corresponding values in females (H: 4.2 ± 0.6 KPa and R: 5 ± 0.5 KPa). Moreover, the slope of pressure-volume curves revealed significantly greater distended vascular compliance in male H than R, and the corresponding females. CONCLUSION: Our findings are supportive of a link between high salt intake and elevated blood pressure as being sex specific, likely involving sex-dependent changes in ultrastructure of the vessels, which ultimately may alter the biomechanics, and thus, the haemodynamic functions of both macro-circulation and micro-circulations.