Modulation of right and left ventricular wall thicknesses in experimental hypertension

Enalapril maleate and hydrochlorothiazide were administered over an 8-week period to groups of Dahl salt-sensitive and Dahl salt-resistant rats receiving either a high (8%) or low (0.4%) salt diet. Regional differences of interventricular septal thickness, left ventricular free wall thickness, right ventricular free wall thickness, right ventricular weight/body weight ratio, left ventricular weight/body ratio, and heart weights were determined. For salt-sensitive rats of both diet groups, lowering of blood pressure induced by either drug was associated with a reduction in cardiac weight which was localized to the left ventricle. For salt-resistant rats, irrespective of diet, the associated reduction of cardiac mass induced by enalapril maleate was largely confined to the right ventricle. Regional changes in tissue thickness were, however, not always associated with corresponding changes in tissue mass or blood pressure. These regional modulations appeared to be quite dependent on salt intake and the nature of the antihypertensive drug, for a given animal type, suggesting that pressure afterload is not the only factor in the pathogenesis of left and right ventricular hypertrophy. The responses of the right ventricle were not necessarily the same as those of the left ventricle to identical dietary and drug regimens. In all animal groups, ventricular mass and tissue thickness did not always change in the same sense, suggesting that alterations in the nature and packaging of the cellular constituents may be induced by the combined actions of the dietary salt and antihypertensive medications.