Multi‐drug‐resistant cells overproduce a 130–180‐kDa integral membrane phosphoglycoprotein known as P‐glycoprotein which acts as an energy‐dependent drug efflux pump. While P‐glycoprotein has been shown to transport hydrophobic anti tumor drugs out of multi‐drug‐resistant cells in tissue culture, its endogenous substrates remain unknown. This report shows that 3H‐corticosterone can specifically photoaffinity label P‐glycoprotein. Furthermore, corticosterone is effluxed from multidrug‐resistant cells by P‐glycoprotein. These data suggest that corticosterone may be an endogenous substrate for P‐glycoprotein. © 1992 Wiley‐Liss, Inc.
ASJC Scopus subject areas
- Cancer Research