Muramatsu M, Fujita A, Tanaka M, Aihara H
Jpn J Pharmacol. 1985 Oct;39(2):217-23. doi: 10.1254/jjp.39.217.
The dissociation constant (Kd) and the maximum number of binding sites (Bmax) of 3H-nitrendipine (3H-NTD) were not altered by neuraminidase (NUase) treatment. The Kd and Bmax values were approximately 0.2 nM and 70 fmoles/mg protein, respectively. The influences of diltiazem on 3H-NTD bindings differed between NUase treated and untreated preparations. Diltiazem increased 3H-NTD (100 pM) binding dose-dependently with a 40% increase at about 10(-6) M in the untreated preparation. After treatment with NUase, a low dose of diltiazem decreased 3H-NTD (100 pM) binding, and the greatest effect was observed at 10(-9) M with a 50% decrease, while at a high dose of diltiazem (10(-6) M), 80% increase of the binding was observed. Scatchard plot analysis indicated that a high dose of diltiazem (10(-6) M) increased only the affinity of 3H-NTD to the binding site in both the NUase-treated and untreated preparations. In the untreated preparation, a low dose of diltiazem (10(-9) M) had no effect on 3H-NTD binding, but in the NUase-treated preparation, diltiazem (10(-9) M) showed opposing effects, namely, an increase and decrease of the binding at low and high concentrations of 3H-NTD, respectively. No straight line was obtained when a hill plot analysis of the effect of diltiazem on 3H-NTD binding was made. These results suggested that diltiazem allosterically regulates dihydropyridine derivative binding, and in this regulation, the concentration ratios between diltiazem and the dihydropyridine derivative is the most important factor. Furthermore, it is suggested that the sialic acid of the proteoglycan is involved in these interactions, especially in the effect of diltiazem on dihydropyridine binding.
神经氨酸酶（NUase）处理并未改变3H-尼群地平（3H-NTD）的解离常数（Kd）和最大结合位点数（Bmax）。Kd和Bmax值分别约为0.2 nM和70 fmol/mg蛋白质。地尔硫䓬对3H-NTD结合的影响在经NUase处理和未处理的制剂之间有所不同。在未处理的制剂中，地尔硫䓬以剂量依赖性方式增加3H-NTD（100 pM）的结合，在约10(-6) M时增加40%。用NUase处理后，低剂量的地尔硫䓬降低3H-NTD（100 pM）的结合，在10(-9) M时观察到最大效应，降低50%，而在高剂量的地尔硫䓬（10(-6) M）时，结合增加80%。Scatchard图分析表明，高剂量的地尔硫䓬（10(-6) M）仅增加了3H-NTD在经NUase处理和未处理制剂中与结合位点的亲和力。在未处理的制剂中，低剂量的地尔硫䓬（10(-9) M）对3H-NTD结合无影响，但在经NUase处理的制剂中，地尔硫䓬（10(-9) M）表现出相反的作用，即在低浓度和高浓度的3H-NTD时分别增加和降低结合。当地尔硫䓬对3H-NTD结合的影响进行Hill图分析时，未得到直线。这些结果表明，地尔硫䓬通过变构调节二氢吡啶衍生物的结合，在这种调节中，地尔硫䓬与二氢吡啶衍生物之间的浓度比是最重要的因素。此外，提示蛋白聚糖的唾液酸参与了这些相互作用，特别是地尔硫䓬对二氢吡啶结合的影响。
