Aims: 

Aging-induced alterations in the vasomotor function of endothelium have been well investigated, whereas modulations of smooth muscle function are less known. We hypothesized that aging alters the magnitude of vasomotor responses to Angiotenzin II (Ang II) and this may correlate to the changes in systemic blood pressure (SBP).

Methods: 

SBP of rats of different ages was measured by an electromanometer. Carotid arteries from newborn (8 days: 8d), young (2 months: 2m), adult (6m) and aged (12m and 24m) rats were isolated and their isometric tensions were measured. Two dose response curves to Ang II were obtained in a sequential manner, 1- and 2-administration (1-Adm and 2-Adm). The expression of AT₁-receptors was visualized by immunohistochemistry.

Results: 

SBP of rats changed with age (8d: 60±17, 2m: 122±8, 6m: 137±10, 12m: 100±7 and 24m: 93±4 mmHg). Contractions of vessels to 1-Adm of Ang II in 8d vessels were significantly less compared to those of 2m, 6m, 12m and 24m, which were similar in magnitude (1.4±0.2 and 5.2±0.6, 5.6±0.4, 5.2±0.5, 5.7±0.4 mN, respectively). Contractions of vessels to 2-Adm of Ang II were significantly reduced at 2m, 6m, 12m and 24m (4.4±0.5; 3.6±0.4; 1.9±0.4, 0.5±0.2 mN), whereas it did not change in vessels of 8d rats (1.28±0.2 mN). The expressions of the AT₁-receptors were significantly reduced as a function of age (8d: 1.5±0.2, 2m: 0.8±0.2, 12m: 0.6±0.3, 24m: 0.4±0.01 pixel).

Conclusions: 

Aging-induced changes in Angiotensin II-induced constrictor responses seem to correspond to changes in blood pressure, but not to the expression of AT₁-receptors.

Support: 

AHA-0855910D, OTKA K71591 and T67984