CHANGES IN THE NATURE OF P-GLYCOPROTEIN GENE TRANSCRIPTS DURING THE DEVELOPMENT OF MULTIDRUG-RESISTANCE IN CHO-CELLS

We have studied the nature of P-glycoprotein gene transcripts in multi drug resistant Chinese hamster ovary cell lines selected in vincristin e. Using a novel, S-35 based, reverse transcription polymerase chain r eaction assay, we have shown that there is a considerable increase in the level of pgp2 gene transcripts, with levels rising to a hundred fo ld those observed in sensitive control cells. The level of pgp1 gene t ranscripts was raised five fold. The levels of pgp3 gene transcripts w ere close to the limits of detection by the assay, but were increased in the more highly resistant cell lines. An increase in the size of th e P-glycoprotein gene transcript was also observed in some of the resi stant cell lines.