RESUMO
Aim To investigate the effects and mechanisms of DMA on cardiac function in cardiomegaly rat isolated hearts.Methods With Langendorff perfusion,the changes in the indicators reflecting cardiac function were observed in cardiomegaly rat isolated hearts.Its probable mechanism was explored with calcium channel blocker and sodium calcium exchange(NCX) blockers.Results DMA(0.5～2 ?mol?L~(-1))enchanced cardiac function and exerted positive effects on LVSP-LVDP,+dp/dt_(max)and-dp/dt_(max) in Langendorff-perfused cardiomegaly rat isolated hearts.The effects of DMA on cardiac function in cardiomegaly rat isolated hearts weren′t blocked by nicardipine-one of calcium channel blockers and were blocked by NiCl_2——one of sodium calcium exchange(NCX) blockers.Conclusion DMA can enhance systolic and diastolic function in cardiomegaly rat isolated hearts.By agitating NCX,DMA enhances cardiac function in cardiomegaly rat isolated hearts,independent of L-calcium channel.
RESUMO
Objective:To observe the effects of active immunization with a synthesized repetitive peptides in the extracellular loops of Na/Ca exchanger(NCX)?1 on cardiac structure and function in rats.Methods:A repetitive peptide of 124 HNFTAGDLGPSTIVGSAAFNMF145 was synthesized,which was in line with the extracellular loops of Na/Ca exchanger(NCX)?1.Healthly male Wistar rats of 2 month age were immunized actively with the synthesized peptide as antigen repeated for 12 weeks.The control group was given Freund's adjuvant only.Specific antibodies were detected by ELISA.The cardiac function was observed by Langendorff isolated heart-perfusing assay and the hearts were prepared for routine histological evaluation.Results:All rats immunized with the peptide developed highly positive autoimmunities,indicated by the antibody titers.After 12 weeks of peptide inoculation,the cardiac functioning indexes including LVSP-LVDP,+dp/dtmax and -dp/dtmax increased much more significantly in immunized group than in control.Histological evaluation showed that the myofilaments of the control group arranged regularly and densely with better continuity,whereas the myofilaments of the immunized group were lined with disorder.Some of those were ruptured.The interstitial lymphocyte infiltration was observed.Conclusion:The results indicate that long term immunization with the synthesized repeatitive peptide in line with the extracellular parts of Na/Ca exchanger(NCX)?1 can enhance both systolic and diastolic function of rat heart,but it can also induce injury in the heart structure.This may relate with an increase of myocardial oxygen consumption owing to a long time and continued excitement of membrane ion transporters as well as their active effect in heart contraction to a larger extent.