Dietary linoleic acid deprivation: an experimental model of salt-sensitive hypertension

The present study investigates arterial blood pressure (BP), renal arachidonic acid cyclooxygenase metabolism and excretory function in rats during dietary linoleic acid deprivation and a concomitant low and high NaCl-intake. Four groups of animals were fed isocaloric diets containing 10 energy (en) % saturated fat and either 5 en % linoleic acid (groups I and III) or 5 en % oleic acid (groups II and IV) over six weeks. In addition, groups I and II received a chronic high intake of sodium (5.4 mmol/24 h) while groups III and IV were NaCl-restricted (average NaCl intake of 0.7 mumol/24 h). Systolic BP significantly increased from 97.0 +/- 1.7 to 112.0 +/- 2.2 mmHg (p less than 0.01) in the salt loaded group II fed the diet deficient in linoleic acid and remained unchanged in the three other groups. Renal cyclooxygenase metabolism was significantly stimulated by sodium restriction and suppressed following dietary linoleic acid deprivation. During infusion of 0.45% saline to a stable increase in body weight of 10%, animals in the linoleic acid deprived groups II and IV excreted significantly less sodium, chloride, and potassium than animals in groups I and III. This impairment in renal excretory function occurred without concomitant changes in RPF, GFR, or UPhos V. It was associated, however, with marked decreases in fractional free water excretion (CH2O/GFR), distal delivery of solute [(CH2O + CCl)/GFR] and with an increase in "distal fractional chloride absorption" [CH2O/(CH2O + CCl)]. Furthermore, linoleic acid deprivation was associated with a significantly enhanced papillary osmolality and papillary sodium, chloride, and potassium concentrations in group II animals as compared to group I.(ABSTRACT TRUNCATED AT 250 WORDS)