Salaices M, Alonso M J, Rico I, Fernández-Alfonso M S, Marín J
Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma, Madrid, Spain.
Brain Res. 1989 Jun 19;490(1):133-40. doi: 10.1016/0006-8993(89)90438-1.
The effects of Bay K 8644 on the reactivity and 45Ca2+ uptake in segments from human cerebral arteries were studied. Bay K 8644 induced concentration-dependent contractions up to 10(-6) M; 10(-5) M produced a reduction of the maximal response. The Ca2+ agonist elicited these contractions by itself, and no previous depolarization was needed. The response to Bay K 8644 was antagonized competitively by nifedipine (5 x 10(-8) and 10(-7) M, pA2 value of 8.17) and non-competitively by verapamil (10(-6), 5 x 10(-6) and 10(-5) M). The contraction induced by 10(-7) M Bay K 8644 was inhibited by a Ca2+-free medium containing 1 mM EGTA. The subsequent cumulative Ca2+ addition, caused concentration-dependent contractions up to 2.5 mM Ca2+, which were reduced by nifedipine (10(-8) and 10(-7) M) or verapamil (5 x 10(-6) and 10(-5) M). When the EGTA concentration in the Ca2+-free solution was reduced to 0.1 mM, contractions induced by Ca2+ up to 5 mM, including 0 Ca2+, were increased with respect to those obtained in the presence of 1 mM EGTA. Basal 45Ca2+ uptake was not modified with Bay K 8644 (10(-6) M) or nifedipine (10(-6) M). K+ (25 and 50 mM) produced an increase on 45Ca2+ uptake, which was potentiated by Bay K 8644 (10(-6) M) and antagonized by nifedipine (10(-6) M); this latter agent reduced the potentiation elicited by the Ca2+ agonist.(ABSTRACT TRUNCATED AT 250 WORDS)
研究了Bay K 8644对人脑动脉节段反应性和45Ca2+摄取的影响。Bay K 8644在浓度高达10(-6) M时可诱导浓度依赖性收缩；10(-5) M时可使最大反应降低。Ca2+激动剂自身即可引发这些收缩，无需预先去极化。硝苯地平（5×10(-8)和10(-7) M，pA2值为8.17）可竞争性拮抗对Bay K 8644的反应，维拉帕米（10(-6)、5×10(-6)和10(-5) M）则可非竞争性拮抗。含1 mM EGTA的无钙培养基可抑制10(-7) M Bay K 8644诱导的收缩。随后累积添加Ca2+，在Ca2+浓度高达2.5 mM时可引起浓度依赖性收缩，而硝苯地平（10(-8)和10(-7) M）或维拉帕米（5×10(-6)和10(-5) M）可使其降低。当无钙溶液中EGTA浓度降至0.1 mM时，与存在1 mM EGTA时相比，Ca2+（高达5 mM，包括0 Ca2+）诱导的收缩增强。Bay K 8644（10(-6) M）或硝苯地平（10(-6) M）对基础45Ca2+摄取无影响。K+（25和50 mM）可使45Ca2+摄取增加，Bay K 8644（10(-6) M）可增强该作用而硝苯地平（10(-6) M）可拮抗；后者可降低Ca2+激动剂引发的增强作用。（摘要截取自250字）
