Raffa R B, Wild K D, Mosberg H I, Porreca F
Drug Discovery Research, R.W. Johnson Pharmaceutical Research Institute, Spring House, PA 19477.
Eur J Pharmacol. 1993 Feb 15;244(3):231-8. doi: 10.1016/0922-4106(93)90148-3.
Dissociation constants (KA) for [D-Pen2,5]enkephalin (DPDPE) inhibition of the electrically evoked twitch of the mouse isolated vas deferens preparation (MVD) were calculated at five temperatures (25, 30, 34, 37 and 40 degrees C). These values were determined from the equiactive concentrations obtained before (A) and after (A') partial irreversible blockade of a fraction of the receptor population by beta-chlornaltrexamine (beta-CNA) plotted as (1/A') where KA = (slope -1)/intercept. The values of KA tended to increase (approximately doubled) over this temperature range, indicating that the affinity of DPDPE for the opioid delta receptor is an inverse function of temperature. From these results, thermodynamic parameters were calculated from a Van't Hoff plot of 1n(KA) against 1/T. The relative magnitudes of the change in enthalpy (delta Ho' = -6.67 kcal mol-1), the change in entropy (delta So' = +0.009 kcal mol-1 degrees K-1) and the change in free energy (delta Go' = -9.43 kcal mol-1) suggest that the interaction between DPDPE and the delta-opioid receptor in MVD is an exothermic exergonic reaction, predominantly enthalpy-driven and results in an increase in the entropy of the system.
在五个温度（25、30、34、37和40摄氏度）下，计算了[D-青霉胺2,5]脑啡肽（DPDPE）对小鼠离体输精管标本（MVD）电诱发抽搐的抑制作用的解离常数（KA）。这些值是根据β-氯诺啡胺（β-CNA）对一部分受体群体进行部分不可逆阻断前后获得的等效活性浓度确定的，以（1/A'）作图，其中KA =（斜率-1）/截距。在这个温度范围内，KA值趋于增加（大约翻倍），表明DPDPE对阿片δ受体的亲和力是温度的反函数。根据这些结果，从ln(KA)对1/T的范特霍夫图计算出热力学参数。焓变（ΔHo' = -6.67 kcal mol-1）、熵变（ΔSo' = +0.009 kcal mol-1 K-1）和自由能变（ΔGo' = -9.43 kcal mol-1）的相对大小表明，DPDPE与MVD中δ阿片受体之间的相互作用是一个放热的放能反应，主要由焓驱动，并导致系统熵增加。
