ACTH hypertension in the rat: role of sodium chloride

Adrenocorticotrophin (ACTH) produces adrenally dependent increases in both blood pressure and salt (NaCl) appetite in the rat. The present study examines the effect of free access to a high intake of NaCl on ACTH hypertension in the rat to test the hypothesis that high NaCl intake would amplify the rise in blood pressure. Either water or 1%NaCl were offered to sham or ACTH treated Sprague-Dawley rats. Subcutaneous injections of synthetic ACTH (0.5 mg/kg/day) for 10 days caused large increases in the intake of both 1%NaCl (+240 +/- 6 ml/day) and water (+45 +/- 4 ml/day), urine volume (1%NaCl + ACTH +182 +/- 4 ml/day, ACTH + water +36 +/- 2 ml/day), adrenal weight (ACTH + water 176 +/- 18, ACTH + 1%NaCl 367 +/- 129 mg/100 g body weight) and maximum systolic blood pressure (SBP) (ACTH + water +18 +/- 5 mmHg; 1%NaCl + ACTH +16 +/- 3 mmHg). Some ACTH + 1%NaCl rats developed severe edema. Thus, free access to NaCl in ACTH treated Sprague Dawley rats did not potentiate the hypertension, but was associated with edema in some animals.