Boschcov P, Paiva A C, Paiva T B, Shimuta S I
Br J Pharmacol. 1984 Oct;83(2):591-600. doi: 10.1111/j.1476-5381.1984.tb16523.x.
Low doses of bradykinin (below 10 nM), as well as of K+ (below 10 mM) induced relaxation, whereas higher doses caused contraction of the rat duodenum. The relaxant responses induced by bradykinin and K+ were not affected by ouabain (1 microM), but pre-incubation with 5.9 mM K+ abolished the responses to that ion but not those to bradykinin. The contractile and relaxant components of the response to bradykinin (but not those to K+) increased with the time elapsed after mounting of the preparation, and this was due to stretching by the load of the recording system. Specific and reversible desensitization (tachyphylaxis) was observed with the contractile response (but not the relaxation) induced by bradykinin. Des-Arg9-bradykinin, an analogue specific for B1-receptors, was much less active than bradykinin, and elicited only a contractile response. Among four bradykinin potentiating peptides that were tested, potentiator C enhanced the relaxation only, whereas BPP5a and captopril potentiated only the contraction and BPP9a potentiated both types of response to bradykinin. Our results support the hypothesis that the relaxant and contractile components of the rat duodenum's response to bradykinin are due to actions at different receptor sites, which can be distinguished by their properties (desensitization) and their different apparent affinities for agonists and for potentiating peptides.
低剂量的缓激肽（低于10 nM）以及钾离子（低于10 mM）可诱导大鼠十二指肠舒张，而高剂量则会导致收缩。缓激肽和钾离子诱导的舒张反应不受哇巴因（1 microM）影响，但预先用5.9 mM钾离子孵育可消除对该离子的反应，而不影响对缓激肽的反应。缓激肽反应的收缩和舒张成分（但钾离子反应的成分不受影响）随着标本制备后时间的推移而增加，这是由于记录系统负荷的拉伸所致。观察到缓激肽诱导的收缩反应（而非舒张反应）存在特异性且可逆的脱敏（快速耐受）现象。去精氨酸9 - 缓激肽是一种对B1受体特异的类似物，其活性远低于缓激肽，且仅引发收缩反应。在测试的四种缓激肽增强肽中，增强肽C仅增强舒张反应，而BPP5a和卡托普利仅增强收缩反应，BPP9a则增强对缓激肽的两种反应类型。我们的结果支持以下假说：大鼠十二指肠对缓激肽反应的舒张和收缩成分是由于作用于不同的受体位点，这些位点可通过其特性（脱敏）以及对激动剂和增强肽的不同表观亲和力来区分。
