RT-PCR identification of murine bcl-x transcripts expressed in FVA cells that were cultured for 2 or 4 hours with EP (designated 2 h⁺ and 4 h⁺, respectively). Reverse transcriptase was used to generate cDNA from total RNA of 2 h⁺ or 4 h⁺ cells. Each reverse transcriptase reaction was divided into three equal aliquots and subjected to PCR amplification using three primer sets. Marker lanes (M) show the 100-bp ladder (GIBCO-BRL), with sizes given on the left. Lanes 1 and 2 represent PCR with primers24 designed to amplify mRNAs for Bcl-X_L (780 bp), Bcl-X_S (591 bp), and Bcl-X_ΔTM (710 bp). Lanes 3 and 4 show samples generated with primers designed to detect mRNA containing an unspliced intronic sequence, ie, the mRNA for Bcl-X²⁶_β (expected size, ∼700 bp). Lanes 5 and 6 represent samples amplified by an additional set of primers designed to generate fragments from all three of the mRNAs for Bcl-X_L (493 bp), Bcl-X_S (304 bp), and Bcl-X_ΔTM (423 bp).25