British journal of clinical pharmacology
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Br J Clin Pharmacol · Feb 1994
Inhibitory effects of calcium antagonists on alpha-adrenoceptor-mediated contraction in the human internal mammary artery.
1. The internal mammary artery has become a preferred coronary bypass graft. Sympathomimetic amines are spasmogens for vasospasm and calcium antagonists are frequently administered drugs perioperatively. ⋯ Pretreatment with nifedipine (200 nM) only slightly inhibited the MO- (1.74 +/- 0.32 vs 2.88 +/- 0.56 g) or NA- (2.43 +/- 0.66 vs 3.60 +/- 0.82 g) induced contraction without statistical significance (P > 0.05). 6. On the other hand, nifedipine only caused 34.49% relaxation in the MO-precontracted and 24.39% relaxation in the NA-precontracted IMAs. In contrast, GTN caused 76.16% (against MO, P < 0.05) or 92.22% (against NA, P < 0.0001) relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)