Carrasquer G, Li M, Yang S, Schwartz M
Department of Medicine, Division of Nephrology, University of Louisville, Louisville, KY 40292, USA.
Biochim Biophys Acta. 1998 Mar 2;1369(2):346-54. doi: 10.1016/s0005-2736(97)00236-8.
In an in-vitro preparation of gastric mucosae of Rana pipiens, the effect of adding melittin to a concentration of 5x10-6 M in the secretory solution on the transepithelial potential difference (PD), resistance (R) and short-circuit current (Isc) was studied. In 20 min, melittin decreased the PD by 9.3 mV and R by 148 ohm cm2. These changes can be explained by a decrease in the resistance, RP, of the paracellular pathway. To determine whether specific-ion pathways were responsible for the decrease in R, the effect of melittin on the partial conductances of Cl-, K+ and Na+ was also studied using the ion substitution method. Melittin decreased the PD response to changes in nutrient Na+, K+ and Cl- and the PD response to changes in secretory Cl-, but did not affect PD responses to changes in secretory Na+ or K+. Therefore, melittin decreased the nutrient membrane partial conductances of Cl-, K+ and Na+ and secretory membrane partial conductance of Cl-, without affecting the secretory partial conductances of Na+ or K+. Initially, melittin increased Isc in regular and Cl--free but not in Na+-free solutions. There was a delayed decrease in Isc. The results indicate that melittin decreases RP, increases the Na+ conductance of the secretory membrane and inhibits, eventually, the Na+/K+-ATPase pump.
在牛蛙胃黏膜的体外制备中，研究了在分泌液中添加浓度为5×10⁻⁶ M的蜂毒肽对跨上皮电位差（PD）、电阻（R）和短路电流（Isc）的影响。在20分钟内，蜂毒肽使PD降低了9.3 mV，R降低了148欧姆·平方厘米。这些变化可以通过细胞旁途径电阻RP的降低来解释。为了确定特定离子途径是否是R降低的原因，还使用离子替代法研究了蜂毒肽对Cl⁻、K⁺和Na⁺的部分电导率的影响。蜂毒肽降低了对营养物质Na⁺、K⁺和Cl⁻变化的PD反应以及对分泌性Cl⁻变化的PD反应，但不影响对分泌性Na⁺或K⁺变化的PD反应。因此，蜂毒肽降低了Cl⁻、K⁺和Na⁺的营养膜部分电导率以及Cl⁻的分泌膜部分电导率，而不影响Na⁺或K⁺的分泌部分电导率。最初，蜂毒肽在正常溶液和无Cl⁻溶液中增加Isc，但在无Na⁺溶液中不增加。Isc有延迟下降。结果表明，蜂毒肽降低RP，增加分泌膜的Na⁺电导率，并最终抑制Na⁺/K⁺-ATP酶泵。
