Hypertension in Diet‐Induced Obese Rats: Neurohumoral Mechanisms Contributing to Blood Pressure

Abstract

The goal of this study was to determine the arterial pressure and neurohumoral response to high fat intake in rats genetically bred for sensitivity to fat-induced obesity (DIO) or resistance to the fat stimulus (DR). Rats were obtained from Charles River Laboratories. Mean arterial pressure was measured using radiotelemetry starting at 10 weeks of age. MAP was monitored during a one week control period with rats on normal chow. During the control period, MAP was significantly higher in the DIO animals (DIO: 115±1 mmHg vs. DR: 100±1 mmHg). Body weight increased 221±9 gm in the DIO rats and 176±9 gm in the DR rats over a six week high fat feeding period. After the high fat diet, MAP was still elevated in the DIO rats at approximately the same levels observed during the pre-fat period (DIO: 116±1 mmHg vs. DR: 103±1 mmHg). Acute ganlionic blockade caused a greater fall in MAP in the DIO rats compared to the DR animals (−48±4 mmHg vs. 33±2 mmHg); blood pressure was reduced to the same level in both groups. Blood samples taken after high fat diet revealed significantly higher levels of plasma aldosterone (158.4±18.6 ng/ml vs. 61.4±12.1 ng/ml), renin activity (8.3±0.69 ng/ml/hr vs. 5±0.57 ng/ml/hr), and insulin (2.41±0.21 ng/ml vs.1.73±0.17) in the DIO rats compared to the DR animals. These data suggest that genes predisposing animals to obesity on a high fat diet can cause neurogenic hypertension independent of dietary fat content.