ACTIVATION OF CREATINE KINASE-B AND PHOSPHOLAMBAN GENE-EXPRESSION IN TRANSFORMED LATISSIMUS-DORSI MUSCLE - EVALUATION OF MESSENGER-RNA BY POLYMERASE CHAIN-REACTION

Latissimus dorsi muscle (LDM) transformation following chronic stimula tion is the critical requirement for its use in cardiac assist procedu res. In order to identify one or two molecular markers that can be use d to effectively monitor the LDM transformation,the modulation in the expression of creatine kinase (CK) and phospholamban (PLB) genes by se mi-quantitative reverse transcriptase polymerase chain reaction (RT-PC R) was examined. Continuous ill situ stimulation of left LDM was perfo rmed in four dogs for a period of 10 weeks after a vascular delay peri od of 2 weeks following surgery. For RT-PCR, gene-specific radiolabele d primers and equal amounts of cDNA synthesized from total RNA extract ed from the LDM biopsies obtained at 4, 7, and 10 weeks of stimulation were used. A 2,G-fold increase in creatine kinase (brain type) (CK-B) mRNA was observed in transformed LDM compared to the control (P=0.004 ) following 10 weeks of stimulation. On the contrary, a 30% decline wa s observed in creatine kinase: (muscle type) (CK-M) mRNA level. An inc rease up to eight-fold was also observed in PLB mRNA in stimulated LDM compared to the contralateral muscle (P=0.002), The PLB mRNA level in transformed LDM reached plateau and became comparable to that of norm al heart after 7 weeks of stimulation, However, a sustained increase i n CK-B mRNA level was observed until 10 weeks of stimulation, The leve l of beta-actin mRNA used as control remained the same in both stimula ted and control samples, Thus the increase in CK-B and PLB mRNA and do wnregulation of CK-M mRNA in transformed LDM, demonstrated here by RT- PCR, indicate a switch from anaerobic to aerobic potential of transfor med LDM along with a change towards slow-twitch phenotype and provide valuable markers to monitor the effectiveness of muscle transformation in cardiomyoplasty. (C) 1996 Academic Press Limited