Analysis of linkage of the ace locus with measures of cardiac hypertrophy in the spontaneously hypertensive rat

1. The effects of genetic factors on cardiac myocyte diameter and other phenotypes of heart size were determined in genetically hypertensive rats. Direct blood pressure, heartweight and cardiac myocyte size were measured at 12 weeks of age in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats and F males derived from these rats. The genotypes of the angiotensin converting enzyme (ACE) gene on rat chromosome 10 were determined by amplification of DNA using the polymerase chain reaction in F animals and were correlated with measures of phenotypes using ANOVA and t- test. 2. Significant correlations between fibre diameter and myocytes and heartweight or left ventricular weight were observed in SHR, WKY and F males. There was no correlation of myocyte size with systolic blood pressure in F rats. ACE genotype was weakly correlated with heartweight, but not correlated with myocardial fibre diameter in F males, suggesting that this gene may primarily cause expansion of extracellular tissue rather than cardiac myocyte size. 3. Genetic factors may influence heart size through effects on the cardiac myocyte or connective tissue elements. Our results suggest that the growth of myocardial fibres and the increase in volume of interstitial elements in the hypertrophic heart are under independent genetic control