Forskolin (FORS) (0.03 to 10 microM) caused a concentration-dependent rightward shifts of the dose-response curves to CaCl2 in the isolated K+-depolarized rat uterus, with apparent, pA2 value of 8.3, but the slope was different from unity (0.55). 2. In presence of Bay K 8644 (10 and 100 nM), the pA2 values for FORS against CaCl2 contractions were reduced in a concentration-dependent manner and increased the slopes of Schild plots to values no longer different from unity. 3. In presence of low Ca2+ concentration (0.22 nM), the potency of FORS in antagonizing CaCl2 contractions was reduced in about 2-fold. 4. FORS (0.3-3 microM) caused a dose- and time-dependent relaxation of sustained contraction induced by CaCl2 (0.5 mM). 5. FORS (0.3 microM) like nifedipine (NIF, 30 pM) caused a concentration-dependent displacement to the right of the dose-response curve to Bay K 8644 (0.1-100 nM) in K+-depolarized preparations. 6. Higher concentration of both FORS (1 and 3 microM) and NIF (0.01 and 0.03 nM) also reduced the maximal response of Bay K 8644. 7. Both drugs caused a concentration-dependent relaxation of uterine muscle contracted by Bay K 8644 (100 nM) and K+ (80 nM), but neither FORS nor NIF discriminated the two types of contraction.
摘要
福司可林（FORS）（0.03至10微摩尔）使离体K⁺去极化大鼠子宫中氯化钙剂量反应曲线浓度依赖性右移，表观pA2值为8.3，但斜率不同于1（0.55）。2. 在存在Bay K 8644（10和100纳摩尔）时，FORS对抗氯化钙收缩的pA2值以浓度依赖性方式降低，且使希尔德图的斜率增加至不再与1不同的值。3. 在低钙浓度（0.22纳摩尔）存在时，FORS拮抗氯化钙收缩的效力降低约2倍。4. FORS（0.3 - 3微摩尔）引起氯化钙（0.5毫摩尔）诱导的持续收缩的剂量和时间依赖性松弛。5. FORS（0.3微摩尔）与硝苯地平（NIF，30皮摩尔）一样，在K⁺去极化制剂中使对Bay K 8644（0.1 - 100纳摩尔）的剂量反应曲线浓度依赖性右移。6. FORS（1和3微摩尔）和NIF（0.01和0.03纳摩尔）的较高浓度也降低了Bay K 8644的最大反应。7. 两种药物均引起Bay K 8644（100纳摩尔）和K⁺（80纳摩尔）收缩的子宫肌肉浓度依赖性松弛，但FORS和NIF均未区分这两种类型的收缩。
