PARATHYROID HYPERTENSIVE FACTOR-LIKE ACTIVITY IN HUMAN ESSENTIAL-HYPERTENSION - RELATIONSHIP TO PLASMA-RENIN ACTIVITY AND DIETARY SALT SENSITIVITY

Objective: To determine the clinical relevance of the newly described circulating pressor factor with parathyroid hypertensive factor (PHF)- like activity. Design: Plasma samples were collected from 94 normotens ive and 93 essential hypertensive subjects, the latter either previous ly defined by dietary salt sensitivity (n = 43), or prospectively stud ied on both low- (< 50 mmol/day) and high-salt (> 200 mmol/day) diets (n = 16). Methods: Blood pressure, demographic factors, plasma renin a ctivity (PRA), urinary electrolyte excretion and bioassayable PHF-like activity were determined in the fasted state on basal and altered die tary salt intakes. Results: Among the normotensive subjects significan tly higher PHF-like activity and reciprocally lower PRA values were ob served in Black versus Caucasian subjects, particularly among females. In the hypertensive subjects PHF-like activity levels were significan tly elevated in the low- (17.1 +/- 1.5 mmHg, n = 34) and normal- (6.7 +/- 1.8 mmHg, n = 36) but not in the high-renin subgroups compared wit h values in the normotensive subjects (1.6 +/- 1.1 mmHg). Similarly, P HF-like activity values were significantly higher in salt-sensitive th an in salt-insensitive hypertensives. Prospectively, PHF-like activity rose significantly with salt loading (4.9 +/- 1.2 to 20.4 +/- 6.2 mmH g) and was positively related (r = 0.648, P < 0.001) to the pressor re sponse to salt. Conclusions: Elevated levels of PHF-like activity are characteristic of the low-renin or salt-sensitive state, or both, and may contribute to the hypertensive process. Elevated PHF-like activity levels found in normotensive subjects may presage the development of low-renin, salt-sensitive hypertension.