EVIDENCE FOR AN NMDA RECEPTOR SUBUNIT IN HUMAN KERATINOCYTES AND RAT CARDIOCYTES

Receptor binding studies have demonstrated the presence of an [H-3]MK- 801 0,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate) bindin g site in human keratinocytes. The affinity found in keratinocytes was lower than that found in brain membranes. Northern blots identified m RNA in human keratinocytes and rat cardiocytes, as well as rat brain, that hybridized with high stringency to a probe for NMDAR1, an NMDA re ceptor subunit. In each tissue, mRNA that hybridized to another glutam ate binding protein that might be part of an NMDA receptor complex, wa s also present. The presence of NMDA or NMDA-like receptors in keratin ocytes and rat cardiocytes together with the low affinity [H-3]MK-801 binding suggests that this protein may be a general channel forming pr otein that is present in many tissues, and forms specific receptors by interacting with additional subunits.