Leszczynski D, Zhao Y, Cathapermal S, Nilsson J, Foegh M L
Department of Surgery, Georgetown University Medical Center, Washington, DC.
Life Sci. 1993;53(22):1663-74. doi: 10.1016/0024-3205(93)90203-f.
We demonstrate that rat heart coronary artery smooth muscle cells express specific binding sites (receptors) for somatostatin-14. The sigmoidal shape kinetics of the somatostatin-14 binding by the cells suggests the presence of either an allosteric binding site or binding sites with different affinities towards the ligand. Scatchard analysis reveals presence of high affinity (Kd = 0.039 x 10(-9)M) and low affinity (Kd = 0.602 x 10(-9)M) binding sites. Somatostatin-14 and Angiopeptin can displace each other from the binding sites. The concentrations of Angiopeptin required to displace 28%-48% of bound somatostatin-14 (10(-9)M) are in the range of 10(-4)-10(-3)M. The concentrations of somatostatin-14 required to displace 8-27% of bound Angiopeptin (10(-6)M) are in the range of 10(-6)-10(-5)M. Thus, somatostatin-14 seems to possess much higher binding affinity than Angiopeptin. Binding of somatostatin-14 and Angiopeptin to rat smooth muscle cells triggers intracellular event(s) leading to inhibition of smooth muscle cell proliferation. Exposure of smooth muscle cells to somatostatin-14 and Angiopeptin decreases amount of phosphorylated tyrosine residues. The effect of somatostatin-14 and Angiopeptin on the expression of phosphotyrosine precedes and is most likely responsible, at least in part, for the inhibition of smooth muscle cell proliferation. This demonstrates that rat heart smooth muscle cells express physiologically active receptor(s) for somatostatin-14.
我们证明大鼠心脏冠状动脉平滑肌细胞表达生长抑素-14的特异性结合位点（受体）。细胞对生长抑素-14结合的S形动力学表明存在变构结合位点或对配体具有不同亲和力的结合位点。Scatchard分析显示存在高亲和力（Kd = 0.039×10⁻⁹M）和低亲和力（Kd = 0.602×10⁻⁹M）的结合位点。生长抑素-14和血管活性肠肽可从结合位点相互取代。取代28%-48%结合的生长抑素-14（10⁻⁹M）所需的血管活性肠肽浓度在10⁻⁴-10⁻³M范围内。取代8%-27%结合的血管活性肠肽（10⁻⁶M）所需的生长抑素-14浓度在10⁻⁶-10⁻⁵M范围内。因此，生长抑素-14似乎比血管活性肠肽具有更高的结合亲和力。生长抑素-14和血管活性肠肽与大鼠平滑肌细胞的结合引发细胞内事件，导致平滑肌细胞增殖受到抑制。将平滑肌细胞暴露于生长抑素-14和血管活性肠肽会降低磷酸化酪氨酸残基的数量。生长抑素-14和血管活性肠肽对磷酸酪氨酸表达的影响先于并至少部分地可能是平滑肌细胞增殖受到抑制的原因。这表明大鼠心脏平滑肌细胞表达生长抑素-14的生理活性受体。
