Angiotensin II (Ang II) is the main mediator of the Renin-Angiotensin-System acting on AT<sub>1</sub> and other AT receptors. It is regarded as a pleiotropic agent that induces many actions, including func...Angiotensin II (Ang II) is the main mediator of the Renin-Angiotensin-System acting on AT<sub>1</sub> and other AT receptors. It is regarded as a pleiotropic agent that induces many actions, including functioning as a growth factor, and as a contractile hormone, among others. The aim of this work was to examine the impact of Ang II on the expression and function of α<sub>1</sub>-adrenergic receptors (α<sub>1</sub>-ARs) in cultured rat aorta, and aorta-derived smooth muscle cells. Isolated Wistar rat aorta was incubated for 24 h in DMEM at 37˚C, then subjected to isometric tension and to the action of added norepinephrine, in concentration-response curves. Ang II was added (1 × 10<sup>−5</sup> M), and in some experiments, 5-Methylurapidil (α<sub>1A</sub>-AR antagonist), AH11110A (α<sub>1B</sub>-AR antagonist), or BMY-7378 (α<sub>1D</sub>-AR antagonist), were used to identify the α<sub>1</sub>-AR involved in the response. Desensitization of the contractile response to norepinephrine was observed due to incubation time, and by the Ang II action. α<sub>1D</sub>-AR was protected from desensitization by BMY-7378;while RS-100329 and prazosin partially mitigated desensitization. In another set of experiments, isolated aorta-derived smooth muscle cells were exposed to Ang II and α<sub>1</sub>-ARs proteins were evaluated. α<sub>1D</sub>-AR increased at 30 and 60 min post Ang II exposure, the α<sub>1A</sub>-AR diminished from 1 to 4 h, while α<sub>1B</sub>-AR remained unchanged over 24 h of Ang II exposure. Ang II induced an increase of α<sub>1D</sub>-AR at short times, and BMY-7378 protected α<sub>1D</sub>-AR from desensitization.展开更多
Desensitization is a process characterized by the loss of cellular response to an agonist when this is present for a long time. α<sub>1D</sub>-adrenergic receptor (α<sub>1D</sub>-AR) desensit...Desensitization is a process characterized by the loss of cellular response to an agonist when this is present for a long time. α<sub>1D</sub>-adrenergic receptor (α<sub>1D</sub>-AR) desensitization is important since this receptor is involved in the contraction of large caliber arteries, such as the aorta. The aim of this research was to evaluate the desensitization of α<sub>1D</sub>-AR due to the endogenous release of norepinephrine in cultured rat aorta. Wistar rat aorta was incubated for 2 h or 24 h in DMEM at 37°C, and then subjected to isometric tension and the action of added norepinephrine, in concentration-response curve (CRC). In some experiments, BMY-7378 (α<sub>1D</sub>-AR antagonist) or 5-methylurapidil (α<sub>1A</sub>-AR antagonist) was used to identify the α<sub>1</sub>-AR involved in the response, or BMY-7378 to protect the α<sub>1D</sub>-AR from desensitization. Results showed that α<sub>1D</sub>-AR was desensitized when the aorta was incubated for 24 h, since the CRC to exogenous norepinephrine showed lower maximal contraction and the curve was displaced to the right, indicating that the receptor involved in contraction was not the α<sub>1D</sub>-AR, as compared to the aorta incubated 2 h. The receptor stimulated by norepinephrine at 24 h was neither the α<sub>1A</sub>-AR, as shown by the lack of displacement of the curve by 5-methylurapidil, but rather it seems that α<sub>1B</sub>-AR is inducing contraction. When the aorta was incubated with BMY-7378 for 24 h, the α<sub>1D</sub>-AR antagonist protected the receptor from desensitization. Endogenous norepinephrine desensitizes α<sub>1D</sub>-AR in the cultured aorta, and the α<sub>1D</sub>-AR is protected by BMY-7378.展开更多
文摘Angiotensin II (Ang II) is the main mediator of the Renin-Angiotensin-System acting on AT<sub>1</sub> and other AT receptors. It is regarded as a pleiotropic agent that induces many actions, including functioning as a growth factor, and as a contractile hormone, among others. The aim of this work was to examine the impact of Ang II on the expression and function of α<sub>1</sub>-adrenergic receptors (α<sub>1</sub>-ARs) in cultured rat aorta, and aorta-derived smooth muscle cells. Isolated Wistar rat aorta was incubated for 24 h in DMEM at 37˚C, then subjected to isometric tension and to the action of added norepinephrine, in concentration-response curves. Ang II was added (1 × 10<sup>−5</sup> M), and in some experiments, 5-Methylurapidil (α<sub>1A</sub>-AR antagonist), AH11110A (α<sub>1B</sub>-AR antagonist), or BMY-7378 (α<sub>1D</sub>-AR antagonist), were used to identify the α<sub>1</sub>-AR involved in the response. Desensitization of the contractile response to norepinephrine was observed due to incubation time, and by the Ang II action. α<sub>1D</sub>-AR was protected from desensitization by BMY-7378;while RS-100329 and prazosin partially mitigated desensitization. In another set of experiments, isolated aorta-derived smooth muscle cells were exposed to Ang II and α<sub>1</sub>-ARs proteins were evaluated. α<sub>1D</sub>-AR increased at 30 and 60 min post Ang II exposure, the α<sub>1A</sub>-AR diminished from 1 to 4 h, while α<sub>1B</sub>-AR remained unchanged over 24 h of Ang II exposure. Ang II induced an increase of α<sub>1D</sub>-AR at short times, and BMY-7378 protected α<sub>1D</sub>-AR from desensitization.
文摘Desensitization is a process characterized by the loss of cellular response to an agonist when this is present for a long time. α<sub>1D</sub>-adrenergic receptor (α<sub>1D</sub>-AR) desensitization is important since this receptor is involved in the contraction of large caliber arteries, such as the aorta. The aim of this research was to evaluate the desensitization of α<sub>1D</sub>-AR due to the endogenous release of norepinephrine in cultured rat aorta. Wistar rat aorta was incubated for 2 h or 24 h in DMEM at 37°C, and then subjected to isometric tension and the action of added norepinephrine, in concentration-response curve (CRC). In some experiments, BMY-7378 (α<sub>1D</sub>-AR antagonist) or 5-methylurapidil (α<sub>1A</sub>-AR antagonist) was used to identify the α<sub>1</sub>-AR involved in the response, or BMY-7378 to protect the α<sub>1D</sub>-AR from desensitization. Results showed that α<sub>1D</sub>-AR was desensitized when the aorta was incubated for 24 h, since the CRC to exogenous norepinephrine showed lower maximal contraction and the curve was displaced to the right, indicating that the receptor involved in contraction was not the α<sub>1D</sub>-AR, as compared to the aorta incubated 2 h. The receptor stimulated by norepinephrine at 24 h was neither the α<sub>1A</sub>-AR, as shown by the lack of displacement of the curve by 5-methylurapidil, but rather it seems that α<sub>1B</sub>-AR is inducing contraction. When the aorta was incubated with BMY-7378 for 24 h, the α<sub>1D</sub>-AR antagonist protected the receptor from desensitization. Endogenous norepinephrine desensitizes α<sub>1D</sub>-AR in the cultured aorta, and the α<sub>1D</sub>-AR is protected by BMY-7378.
