EFFECTS OF CHRONIC RIGHT-VENTRICULAR PRESSURE-OVERLOAD ON MYOCARDIAL GLUCOSE AND FREE FATTY-ACID METABOLISM IN THE CONSCIOUS RAT

Objective: The aim was to investigate the effects of chronic right ven tricular pressure overload on myocardial glucose and free fatty acid m etabolism in the right ventricular free wall, ventricular septum, and left ventricular free wall. Methods: Using a glucose analogue, C-14-2- deoxyglucose (C-14-DG), and a fatty acid analogue, C-14-beta methylhep tadecanoic acid (C-14-BMHDA), quantitative autoradiography was perform ed in conscious rats with 4 week pulmonary artery constriction. Result s: In rats with chronic pulmonary artery constriction, right ventricul ar peak systolic pressure and right ventricular weight to body weight ratio increased by 88% and 127%, respectively, compared with sham oper ated rats (P<0.01 for each). In the right ventricular free wall, C-14- DG deposition increased but C-14-BMHDA accumulation did not differ in the chronic pulmonary artery constricted rats compared with sham opera ted rats [212(SEM 27), n = 6 nu 101(15) nCi . g(-1), n = 4, P < 0.01, and 406(40), n = 6, nu 333(48) nCi . g(-1), n = 4, NS, respectively]. In sham operated rats, C-14-DG and C-14-BMHDA deposition did not diffe r between the ventricular septum and the left ventricular free wall. I n contrast, C-14-DG and C-14-BMHDA accumulations were lower in the ven tricular septum compared with the left ventricular free wall wall in c hronic pulmonary artery constricted rats. Myocardial blood flow assess ed by C-14-iodoantipyrine was homogeneously distributed throughout bot h ventricles. Conclusions: Chronic right ventricular pressure overload increases myocardial glucose uptake and/or its phosphorylation in the right ventricular free wall, and alters the regional profiles of subs trate use in the ventricular septum and left ventricular free wall des pite the homogeneous blood flow distribution. The results of the acute right ventricular pressure overload study, in which only right ventri cular C-14-BMHDA deposition was increased compared with controls, sugg est that the findings obtained from chronic pulmonary artery constrict ed rats cannot be explained by increased right ventricular pressure al one.