Abstract 347: Comparative Study of Cardiovascular Morphology in Hypertensive, Insulin Resistant and Middle-aged Rats

Abstract

The objective of this study was to compare the effect of insulin resistance, hypertension and aging on cardiac fibrosis and intramyocardial arteries (IMA). Twenty eight male rats were divided into four groups: control (CON), insulin resistance induced by monosodium glutamate (MSG) administered in neonatal period, spontaneously hypertensive rats (SHR), middle-aged rats (MAR). The first three groups were 22 weeks-old and the older group was 30 weeks-old. The heart was fixed and stained with picro Sirius red to evaluate myocardial collagen density. The lumen diameter, media thickness and media cross- sectional area (CSA) of the IMA were measured with the Image Pro Plus image analysis software. The Lee index was slightly increased in MSG group. The systolic blood pressure was significantly elevated in SHR group (CON 113±2, MSG 122±3, SHR 202±3, MAR 115±3 mmHg). The diameter of the IMA was significantly smaller in SHR (29.8±2.4 μm, p<0.01) vs MAR (35.3±2.2 μm), CON (34.0±2.3 μm) and MSG (34.7±2.4 μm). The media-to-lumen ratio was 29.5 ± 1.2% in CON, 39.8 ± 1.3% in MSG, 30.3 ± 0.6% in MAR and 46.5 ± 4.0% in SHR (P<0.001 vs CON/ MAR, P<0.01 vs MSG). The CSA of IMA was significantly increased in SHR and MSG compared to CON showing growing index of 38.5 and 33.0%, respectively. Interstitial subendocardial collagen density of the left ventricle was 2.8±.0.3% in CON, 3.1±.0.7% in SHR, 2.6±0.6 in MAR and 4.0±.0.8% in MSG (P<0.05 vs SRH, P<0.01 vs CON and MAR).The perivascular collagen density was greater in MSG group (48.4±.2.3%, p<0.001 vs other groups) but was also significantly increased in SHR (42.6±.2.3%) and MAR (36.4±1.4 %) groups compared to CON (29.8±.3.0%, p<0.01). In conclusion, hypertrophic vascular remodeling was more associated to hypertension while cardiac fibrosis was more observed when insulin resistance and obesity were present. There were no significant cardiovascular changes in older animals without hypertension and insulin resistance.