Changes Of Plasma And Myocardial ANP And BNP And Their Receptors In Spontaneously Hytertensive Rats

ObjectiveTo investigate the changes of plasma and myocardial atrial natriuretic peptide(ANP) and brain natriuretic peptide(BNP) and expression of their receptors on left ventricular in spontaneously hypertensive rats .To explore the pole of natriuretic peptide system in the development of hypertension.MethodMale SHRs were randomly divided into 4 weeks, 8 weeks, 12 weeks, 18 weeks, 24 weeks, 30 weeks (6 groups ,n = 8), and age and sex matched WKYs rats were set as control(n=8).The systolic blood pressure(SBP) was measured by tail-cuff plethysmography.All rats were sacrified after anesthetized and weighted and haemospasia from abdominal aorta to detect the plasma concentration of ANP and BNP. Content of left ventricular mass (LVM), left ventricular mass index (LVMI) were measured and calculated.Morphological characteristics of left ventricular was evaluated with HE.ELISA test were performed to detect the concentration of ANP and BNP in both plasma and left ventricular. The expression of myocardial natriuretic peptide A receptor (NPR-A), C-type receptor (NPR-C) were assessed with both immunohistochemistry straining and Western Blot analysis.Results1.Body weight(BW) in both SHR and WKY group was increased with age.At 4,8,12,18,24,30 weeks, BW in SHR group are lower than in WKY group, but from 8 weeks , LVM, LVMI in the SHR group were significantly higher than that of WKY group (P <0.01). There was no obvious difference between SHRs and WKYs at 4 week on SBP((P>0.05), but SHRs showed higher SBP than WKYs since 8 weeks(P<0.05).The blood pressure of SHRs increased by week(P<0.05).2.The concentration of BNP in plasma and left ventricular of SHRs were higher than WKYs at 4,8,12,18,24 ,30 weeks(P<0.01),both of the indexs in SHRs increased by week(P<0.05).There was no significant difference between SHRs and WKYs on both of plasma and left ventricular ANP(P>0.05).3.With immunohistochemistry straining and Western Blot,the protein expression of NPR-A in left ventricular myocardium in SHRs increased first with ages((highest at 18 weeks)and then decreased.However the left ventricular myccardium of NPR-A in WKYs had no change(P>0.05).4.The left ventricular myocardium of NPR-C in SHRs decreased by week(P<0.05),but the left ventricular myocardium NPR-C in WKY had no significant difference(P>0.05).Conclusions1.The plasma and left ventricular BNP in SHR group increased at prehypertension and also increased by week, the left ventricular NPR-C firstly increased and then decreased gradually; the increase in plasma BNP maybe related to the reduction of NPR-C.2.The left ventricular NPR-A in SHR group within 30 weeks old firstly increased and then decreased.NPR-A may play certain effect in the early maintenance of normal blood pressure and resistance to the left ventricular hypertrophy.3.BNP / NPR-A, NPR-C play a role in hypertension and cardiac hypertrophy ,and have a certain theoretical significance and practical value in prevention and treatment of hypertension in the future.