Lindbom L, Persson M G, Ohlén A, Borgström P, Gustafsson D
Department of Physiology I, Karolinska Institutet, Stockholm, Sweden.
J Cardiovasc Pharmacol. 1990 Apr;15(4):592-7. doi: 10.1097/00005344-199004000-00011.
The effects of felodipine, a vasoselective dihydropyridine calcium antagonist, on microvascular dynamics were investigated in skeletal muscle. The diameters of the transverse (10-28 microns) and terminal (4-8 microns) arterioles, located at the immediate precapillary level in the rabbit tenuissimus muscle, were registrated by intravital microscopy. Topical application of felodipine (10(-7)-10(-5) M) induced a concentration-dependent vasodilation of both arteriolar generations. The steady state response at 10(-7) M revealed a relatively more pronounced dilatation of transverse (92 +/- 30% increase in diameter) than of terminal arterioles (44 +/- 12%). This is in contrast to muscle exercise, which elicits a more pronounced dilatation of terminal (260 +/- 39% increase) than of transverse arterioles (103 +/- 15%). Vasomotor nerve stimulation evoked a frequency-dependent constriction both in the absence and presence of felodipine (10(-6) M). However, the vasodilatory response elicited by graded perfusion pressure reductions was eliminated in the presence of felodipine (10(-7) M). Thus, the vasomotor nerve response was better preserved than the autoregulatory response in the presence of the calcium antagonist. The results indicate that felodipine dilates arterioles via an inhibition of myogenic vascular reactivity, which supports previous results obtained both in vivo and in vitro.
研究了血管选择性二氢吡啶类钙拮抗剂非洛地平对骨骼肌微血管动力学的影响。采用活体显微镜记录家兔细薄肌中位于毛细血管前水平的横向（10 - 28微米）和终末（4 - 8微米）小动脉的直径。局部应用非洛地平（10⁻⁷ - 10⁻⁵M）可引起两代小动脉浓度依赖性血管舒张。10⁻⁷M时的稳态反应显示，横向小动脉的扩张（直径增加92±30%）比终末小动脉（44±12%）更为明显。这与肌肉运动相反，肌肉运动引起终末小动脉（直径增加260±39%）比横向小动脉（103±15%）有更明显的扩张。在有无非洛地平（10⁻⁶M）存在的情况下，血管运动神经刺激均引起频率依赖性收缩。然而，在非洛地平（10⁻⁷M）存在的情况下，分级降低灌注压引起的血管舒张反应被消除。因此，在钙拮抗剂存在的情况下，血管运动神经反应比自身调节反应保存得更好。结果表明，非洛地平通过抑制肌源性血管反应性使小动脉扩张，这支持了先前在体内和体外获得的结果。
