Does Pulse Wave Velocity Reflect Elasticity of Abdominal Aorta of Hypertensive Fowl?

Abstract

Chickens (males more than females) have maturation/age-dependent high blood pressure (BP) and neointimal plaques in the lower segment of the abdominal aorta (AbA) that partly resemble atherosclerotic lesions in mammals. In humans, pulse wave velocity (PWV) increases with aging and hypertension and is used as a measure of stiffness of central arteries. Using a catheter that holds two intravascular pressure transducers at a designated distance, we investigated in maturing/aging chickens whether PWV of AbA correlates with changes in elastin (dry weight of the residue), collagen (hydroxyproline assay), or protein levels in isolated and homogenized AbA media. We found that male chicks (6–7 wk old) had higher (P < 0.01) PWV (m/s) (9.3 ± 0.8) than females (6.1±0.5). PWV remained high in males (13–66 wk); in females, it increased with maturation (13 wk, 9.6 ± 0.9) but dropped significantly in sexually mature birds (27–44 wk; 6.7 ±0.4). With maturation/aging, collagen levels progressively increased, whereas elastin decreased, in AbA media of males (less markedly in females). Protein levels in AbA media were significantly higher in male chicks and continued to increase, while in females, they dropped after sexual maturation, similar to the finding for PWV. These results suggest that sustained high BP in males may cause medial hypertrophy, elastic module fatigue, and increased collagen levels. PWV is already higher in male chicks when elastin and collagen levels are similar in both sexes, suggesting that a factor other than elastin/collagen ratio may be the important determinant of PWV. The effects of female hormones on arterial stiffness, PVW, and medial protein levels remain to be examined. Supported by NIH grant HL52881.