ABSOLUTE MORPHOMETRIC STUDY OF MYOCARDIAL HYPERTROPHY IN EXPERIMENTAL-HYPERTENSION .1. DETERMINATION OF MYOCYTE SIZE

Abstract

A method for determining the mean absolute volume of a specific population of cells within a tissue is described and applied to the measurement of endocardial and epicardial myocytes in the left ventricle of normal and hypertensive rats. The technique, based on nuclear counts per unit area in tissue slices of different known thicknesses, measures the mean cell volume per nucleus independent of previously unknown nuclear dimensions and systematic counting errors. Duplicate determinations, demonstrating reproducibility, were made in mutually perpendicular longitudinal and transverse sections of the myocardium. Combining these light microscopic measurements with EM data enabled the evaluation of the mean diameter and length of the cylindrical myocyte nuclei showing those in epicardial cells to be significantly longer than the nuclei in endocardial cells. It was estimated that 2-4% of ventricular myocytes are binucleate. After 1-4 wk of hypertension, induced by constriction of the left renal artery, endocardial myocytes were enlarged 21%, from 10,370 .+-. 410 to 12,520 .+-. 490 .mu.m3, while epicardial myocytes showed a 37% hypertrophy, from 12,600 .+-. 1600 to 17,300 .+-. 1100 .mu.m3. The availability of a reliable determination of cell volume will make possible the interpretation of much biochemical, functional and morphometric data at the whole cell level.