Study Of The Regulation Of Recombinant Human Relaxin On The Activity Of The Protein Kinase G In The Rabbit Model With Diastolic Heart Failure

Objective:With the aging of society becoming more and more serious,the proportion and incidence of diastolic heart failure(DHF)increase year by year,and relaxin has been found to have cardiovascular protection in recent years.Our previous studies have found that relaxin can improve diastolic function in the DHF rabbit model,but its specific mechanism is sill unknown.In this study,we investigate the effect of human recombinant relaxin(RLX)on the activity of protein kinase G(PKG)in cardiac tissue of rabbits with diastolic heart failure(DHF)and aimed to reveal the pathophysiological mechanism of recombinant human relaxin in improving diastolic function in DHF.It further provides an important experimental basis for clinical targeted therapy of DHF.Methods:1.DHF rabbits model was established by abominal aorta constriction.Forty-two New Zealand rabbits were randomly divided into sham operation group(n=6),DHF group(n= 12),low RLX dose group(30μg/kg·d,n=12),high RLX dose group(98μg/kg·d,n=12).2.At the 8th week after operation,to kick out the rabbits that died after operation and don’t correspond to DHF diagnosis standard.The RLX drug was administered by ear vein injection.The RLX low-dose group was given 30 μg/kg·d and the high-dose group was 98 μg/kg·d.The rabbits were continuously administered via the rabbit ear vein for 2 weeks.3.At the tenth week after operation,to assess the levels of BNP and RLX by ELISA in serum sapmles extracted from each group.Then to prepare 10%heart muscle homogenate of each group and to detect the content of 3-NT、NO、cGMP and PKG also by ELISA.Result:1.After 8 weeks,10 rabbits die after surgery and 4 ones don’t meet the DHF criteria.They are kicked out,and the remaining 28 rabbits are selected into investigation(sham group n=6,DHF group n=6,RLX small dose = 8,RLX large dose = 8).2.The BNP and 3-NT levels was significantly higher(p<0.05)while NO、cGMP、PKG content was significantely lower in DHF group、Low RLX dose group、high RLX dose group than in sham operation group(p<0.05).The NO、cGMP、PKG content was siggificantely higher[(18.70±0.27)μmol/Lvs(16.38±0.16)μmol/L,(10.63±0.34)nmol/Lvs(9.15±0.27)nmol/L,(528.58±3.66)U/L vs(493.26±5.68)U/L,p<0.05]while 3-NT levels was significantly lower in high RLX dose group than in DHF group(p<0.05)..3.Mysson staining showed that the myocardial interstitial fibrosis in the RLX low-dose group and the RLX high-dose group was significantly lower than that in the DHF group.The most significant improvement was in the RLX high-dose group,which showed a marked decrease in collagen fiber content.The chronic inflammatory cell infiltration is reduced,and the myocardial cell volume and cytoplasm are close to the sham group.Conclusion:High-dose RLX reduces the nitrosative/oxidative strss and increases NO bioavailability and PKG activation which contributes to antagonisting myocardial fibrosis and improving diastolic function probably through NO-cGMP-PKG signal pathaway in DHF rabbits.