Elevated AT₁ Receptor Protein but Lower Angiotensin II-Binding in Adipose Tissue of Rats with Monosodium Glutamate-Induced Obesity

Age-related hypertrophy of adipose tissue has been associated with a significant decrease in the number of angiotensin II receptors. The aim of this study was to investigate the characteristics of angiotensin II receptors in hypertrophic adipose tissue in animal obesity model using rats postnatally treated with monosodium glutamate. Angiotensin II is known to induce hypertrophy in several tissues of the cardiovascular system and might do the same in fat tissue. The expression and binding properties of angiotensin II AT₁ receptors in epididymal fat tissue of adult rats were studied using membrane-binding, RT-PCR, and immunoblotting. The amount of AT₁ receptor mRNA did not differ significantly between obese and control rats. Despite that glutamate-treated rats displayed approximately 4-times more AT₁ receptor immunoreactive protein content in fat tissue cell membranes than the controls did. In contrast, binding experiments showed a significant (40.3 ± 6.2 %) decrease of ¹²⁵I-Sar¹-Ile⁸-angiotensin II-binding to fat tissue cell membranes in obese rats compared to controls. In conclusion, the present study provides evidence for the low binding properties associated with an accumulation of AT₁ receptor protein in cell membranes of the fat tissue of rats with glutamate-induced obesity. Discrepancies among angiotensin II-binding, AT₁ receptor protein, and AT₁ receptor mRNA levels indicate a possible defect in the receptor protein, which remains to be identified. The results obtained support a role of angiotensin II and AT₁ receptors in the pathogenesis of obesity.

Key words:

AT₁ Receptor - Fat Tissue - MSG Rat

References

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