Salt-sensitive hypertension in (mREN-2)27 transgenic rats

The (mREN-2)27 transgenic model of hypertension was developed to investigate the effect of genetic over activity of angiotensin II systems as a contributing factor in the development of arterial hypertension. In this model, transgene-positive rats demonstrate elevated renin-angiotensin system activity not only in the circulatory system but also in adrenal gland, reproductive organs, and brain. Since evidence indicates that angiotensin peptides and osmotic stimuli interact synergistically to produce exaggerated behavioral, endocrine, and cardiovascular effects, we examined the effect of salt consumption on arterial pressure, plasma vasopressin, and body fluid balance in male (mREN-2)27 transgene-positive and -negative rats. Four days of drinking 2% NaCl increased mean arterial pressure from 165 +/- 10 to 199 +/- 7 mm Hg in transgene-positive rats. In contrast, transgene-negative rats showed no change in arterial pressure (126 +/- 5 to 128 +/- 3 mm Hg). Plasma vasopressin levels were significantly elevated only in transgene-positive rats, whereas pituitary levels of vasopressin were significantly lower in transgene-positive rats compared with transgene-negative controls (18 +/- 3 and 118 +/- 14 ng, respectively). Although transgene-positive rats consumed significantly more 2% NaCl than did transgene-negative rats, during this period 24-hour sodium balance did not differ between the groups. Since fluid and electrolyte balance is similar between the two groups of rats, the data suggest that transgene-positive rats may be more sensitive to the effects of increased NaCl intake in terms of both endocrine and cardiovascular responses.