Rapid determination of membrane transport parameters in adherent cells

Reported here is a new method that permits rapid (approximately 5 s) determ inations of membrane transport phenomena in cells grown in monolayers at th e base of 17-mm glass scintillation vials. The method is convenient, cost e ffective and requires no special apparatus. Initial uptake rates, steady-st ate and free substrate levels are demonstrated in ZR-75-1 breast cancer and Chinese hamster ovary cell lines using methotrexate, a model agent transpo rted by the reduced folate carrier The technique should be applicable to th e study of the transport properties in a broad range of substrates and cell s in monolayer culture.