ABSTRACT
In order to explore the activity of a peptide containing rat sodium pump α2 subunit M1-M2 extramembrane fragment (RES2 derivative) in vitro, the peptide (Leu-Ala-Ala-Met-Glu-Asp-Glu-Pro-Ser-Asn-Asp-Asn-Gly-Gly-Gly-Ser) was synthesized by peptide synthesizer with Fmoc method and purified by high performance liquid chromatography (HPLC). Its binding activity was identified by radioligand-receptor binding assay (RRA) and its bioactivity was measured by erythrocyte (86)Rb uptake. The results of saturation binding experiment and competitive binding experiment showed that the synthesized RES2 derivative had the capability to bind to (3)H-ouabain. The dissociation constant (K(d)) was 38.46 nmol/L and IC(50) was 6.353 nmol/L. Erythrocyte (86)Rb uptake experiment showed that the RES2 derivative blocked the inhibitory effect of ouabain on the sodium pump on erythrocyte membrane in a dose-dependent manner. The results showed that the RES2 derivative is capable of binding to ouabain and improving the activity of sodium pump on erythrocyte membrane, suggesting that the RES2 derivative might become an effective antihypertensive drug in the future.