[Vasodilators in isolated human radial arteries]

This paper was designed to evaluate the effectivity of several vasodilators, applied topically, to attenuate the hyperreactivity of radial arteries (RA) implanted as aorto-coronary bypass. Remnant segments of the RA were obtained from 20 operations, and each of the segments was divided into 4 rings. The rings were incubated for 30 minutes in control conditions (n = 20) or in presence of 30 microM of Diltiazem (DILT, n = 6), 30 microM of mibefradil (MIBE, n = 4) or a mixture of 30 microM of verapamil + 30 microM of nitroglycerin (VP-NTG, n = 6). A subsequent exposure to KCl 80 mM (in absence of vasodilators) evoked a sustained contraction in control rings, which was attenuated by 35 +/- 9% by DILT, 48 +/- 13% by VP-NTG and by 69 +/- 20% by MIBE (p < 0.05). Preincubation with vasodilators also attenuated the rate and intensity of rhythmic contractions of the RA. In rings that were cold-stored during 24 hs and then restimulated with KCl 80 mM the depressing effect was still evident: DILT 53 +/- 6%, VP-NTG 46 +/- 14% and MIBE 61 +/- 9% (p < 0.05). The effect of MIBE was more intense and persistent than that of DILT or VP-NTG, even at concentrations eliciting a similar initial depression of contraction. It is concluded that the exposure to vasodilators during a period equivalent to the duration of the surgical preparation of the RA produces an attenuation of the arterial reactivity that might provide an additional protection against RA spasm during the immediate postoperative period.