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 (R A) implanted as aorto-coronary bypass. Remnant segments of the RA were obta ined 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 mu M of Diltiazem (DILT, n = 6), 30 mu M of mibefradil (M IBE, n = 4) or a mixture of 30 mu M of verapamil + 30 mu M of nitroglycerin (VP-NTG, n = 6). A subsequent exposure to KCl 80 mM (in absence of vasodil ators) evoked a sustained contraction in control rings, which was attenuate d 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 intens ity of rythmic contractions of the RA. in rings that were cold-stored durin g 24 hs and then restimulated with KCl 80 mM the depressing effect was stil t 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 cont raction. It is concluded that the exposure to vasodilators during a period equivalent to the duration of the surgical preparation of the RA produces a n attenuation of the arterial reactivity that might provide an additional p rotection against RA spasm during the immediate postoperative period.