Patent ID: 7396658

Claim:
An assay for screening a test substance for hypothalamic inhibitory factor (HIF) inhibitory activity of an ouabain-resistant Na + —K + -ATPase, comprising the steps of: (a) contacting liposomes containing, or cells expressing or containing, the ouabain-resistant Na + —K + -ATPase with the test substance in the presence of a compound comprising isotopic Rb + , under suitable conditions for isotopic Rb + uptake by the liposomes or the cells; (b) measuring or detecting the amount of the isotopic Rb + present in the liposomes or the cells; and (c) comparing the amount of the isotopic Rb + present in the liposomes or cells measured or detected in step (b) with a measured or detected amount of isotopic Rb + obtained by contacting liposomes containing, or cells containing or expressing, ouabain-resistant Na + —K + -ATPase with HIF in the presence of the compound comprising isotopic Rb + under comparable conditions, thereby determining whether the test substance exhibits HIF inhibitory activity.