Porcine coronary artery pharmacodynamics in vitro evaluated by a new intravascular technique: relation to axial stretch

A new intravascular balloon catheter-based technique, impedance planimetry and the wire-mounted isometric tension technique commonly employed to study vessel pharmacodynamics in vitro, were compared. Porcine left anterior descendent coronary artery reactivity to nifedipine was assessed and the influence of 20% axial stretch was investigated. There were no histological differences between segments where the impedance planimetry balloon had been inflated and untouched segments. EC50 values differed significantly between the three procedures applied: The isometric method (n = 7): 2.54 +/- 0.44.10(-9) M; nonstretched arteries by the impedance planimetric method (n = 7): 1.99 +/- 0.40.10(-8) M; arteries 20% axially stretched (n = 7): 2.00 +/- 1.36.10(-7)M (isometric and nonstretched: p < 0.05; isometric and stretched: p < 0.001; nonstretched and stretched: p < 0.05). Maximal relaxant responses to nifedipine were 91.8 +/- 2.1% (isometric method), 105.1 +/- 2.3% (nonstretched), and 104.9 +/- 7.7% (stretched) (ANOVA, p = 0.11). In stretched arteries, the initial 12-min response to an increased dose of nifedipine was more rapid than the response of nonstretched arteries at a concentration of 1.10(-7) M (p = 0.038) and had a nonsignificant tendency toward a more rapid response at other concentrations. Resting tone could not be demonstrated and time control experiments showed no change in the maximal vessel response to potassium with any of the three methods. A new method in the evaluation of artery pharmacodynamics in vitro was presented. The study demonstrated that axial stretching of an artery has impact on the pharmacodynamic reactivity to nifedipine in porcine coronary arteries. Further studies are needed to evaluate the impact of the method on endothelial function.