WISTAR FATTY RAT IS OBESE AND SPONTANEOUSLY HYPERTENSIVE

The purpose of this study was to determine whether genetically obese W istar fatty rats have higher blood pressure than their lean littermate s and if so to elucidate the mechanism of this obesity-related hyperte nsion. We measured blood glucose and plasma insulin levels, blood pres sure, and catecholamine and sodium excretions in age-matched female Wi star fatty and lean rats. After 12 weeks of age, the body weight of Wi star fatty rats was significantly greater than that of their lean coun terparts. Fasting blood glucose and plasma insulin concentrations were higher in the fatty than the lean rats throughout the observation per iod (8 to 24 weeks of age). Systolic blood pressure of fatty rats meas ured by the tail-cuff method was similar to that of lean rats at 8 wee ks of age (135+/-2 [mean+/-SEM] versus 134+/-3 mm Hg) but significantl y higher at 16 (158+/-2 versus 136+/-3 mmHg, P<.01) and 24 (166+/-5 ve rsus 142+/-2 mm Hg, P<.01) weeks of age. Urinary norepinephrine excret ion was significantly increased in the fatty rats at both 16 (1755+/-1 73 versus 977+/-128 ng/24 h, P<.05) and 24 (1907+/-283 versus 737+/-17 3 ng/24 h, P<.01) weeks of age. The ratio of urinary norepinephrine ex cretion to body weight was also significantly increased in the fatty r ats. These results show that with increasing body weight Wistar fatty rats develop hypertension, which may be attributable to an increased s ympathetic nerve activity. Since these characteristics are similar to those observed in human obesity-related hypertension, we consider that this rat may be a good model for further analysis of the mechanism of obesity-related hypertension.