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Fowl (males more than females) show maturation-dependent rises in blood pressure (BP) and formation of neointimal plaques (NPs), resembling balloon catheter injury-induced neointima, in the abdominal aorta (AbA) just above the bifurcation. The plaque comprises neointimal cells containing abundant endoplasmic reticulum and extracellular matrix. Hence, we investigated whether rapid incremental BP increases in male chicks trigger NP formation, possibly via endothelial injury in hemodynamically selective areas. In 6-wk-old chicks (n ϭ 8) treated 4 wk with solvent (Sv; minipump) or arginine supplement (Arg; 0.3% in drinking water), BP increased from 140 Ϯ 5 to 159 Ϯ 4 (Sv) and from 138 Ϯ 4 to 157 Ϯ 3 (Arg) mmHg, whereas propranolol treatment (Prop, 8 mg⅐kg Ϫ1 ⅐day Ϫ1; minipump) prevented the rise. Arg and Prop groups had, respectively, 73% and 77% smaller (P Ͻ 0.05) NP areas and 19% and 25% less (P Ͻ 0.01) AbA medial thickness than Sv controls. In 16-wk-old cockerels, established BP remained high after Sv and Arg treatments. In the Prop group, BP decreased, but neither NP area nor medial thickness was lower than in the Sv group, whereas the Arg group showed greater NP area and medial thickness. Pulse pressure, determined by intravascular transducer, increased as the pulse wave descended the aorta. The results suggest that maturation-dependent rises in BP in chicks may trigger NP formation in the lower segment of the AbA, which was prevented by inhibition of BP increase, or via a possible increase in nitric oxide availability. BP reduction exerts no effect once BP reaches a plateau. Involvement of endothelial injury leading to NP formation and hemodynamic forces selective for the lesion-prone area remain to be determined. arginine supplement; nitric oxide; hypertension; atherosclerosis; fowl model; pulse pressure; endothelial dysfunction; endothelial nitric oxide synthase uncoupling BIRDS, particularly fowl, have higher blood pressure (BP) than most mammals. In both male and female fowl, BP is already ϳ150 mmHg at 2-3 wk after birth, and at plateau levels, mean BP is higher in males (194 Ϯ 4.6 mmHg) than in females (169 Ϯ 3.1 mmHg) (13,29,30). In males, BP tends to increase with maturation and/or age, whereas an age-dependent change is not clear in females (30). Before sexual maturation, vascular neointimal plaques (NPs), comprising deformed endothelial cells, proliferating neointimal cells of synthetic phenotype, increased endoplasmic reticulum, and abundant extracellular matrix, are spontaneously formed without a high-cholesterol or high-fat diet (30). The NP lesions are seen in the abdominal aorta, most frequently just before the aortic bifurcation into the ischiadic arteries (referred to as the lesion-prone area); the size of the NP area increases with maturation and/or age, whereas vascular smooth muscle (SM) exhibits adaptive hypertrophy (30). In humans, aging and hypertension are major factors in the induction of arterial hardening (6, 28), and increased brachial pulse pressure (PP), aortic pulse wave velocity ...

Before sexual maturation, chickens (Gallus gallus) show high blood pressure (BP) and neointimal plaques in the lower abdominal aortae (AbA). We investigated age/sex-related changes in pulse wave velocity (PWV), elastin, collagen, and protein levels in AbA, and cardiac morphology to determine whether PWV increases during incremental increases in BP of maturing fowl, while arterial stiffness becomes dominant with aging. PWV (m/s) was significantly greater in male chicks (6-7 wk, 9.3 ± 0.8; females, 6.1 ± 0.5) and remained high in cockerels (13 wk), young (27-28 wk), and adults (44-66 wk). PWV increased in prepubertal pullets (10.0 ± 0.9), dropped significantly in young hens, and remained low in adults. In contrast, medial thickness, protein levels, and collagen levels increased, while elastin/collagen ratios decreased, with maturation/aging. Males had heavier ventricular mass and thicker ventricular walls than females at all ages; left ventricular thickness decreased with maturation/aging. Thus, sustained high BP may have caused progressive medial hypertrophy, increased aortic rigidity, and enlarged hearts with left ventricular dilation. PWV of AbA was already greater in male chicks at an age when both sexes have similar collagen levels and low protein levels, suggesting that a factor other than structural stiffness may be an important determinant of PWV.

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