Influence of renal prostaglandins and dietary linoleate on hypertension in Dahl S rats.

Kidney prostaglandlns appear to bare powerful Influences on Nad-Induced hypertension.In quick-frozen kidneys, the concentration of prosUglandin E, (PGE,) in the renal papilla is 60% lower in Dahl S rats than in Dahl R rats (17 ng/100 mg TS 42 ng/100 mg,p < 0.01) when both S and R rats are fed a 0.3% low NaCI diet.When S and R rats eat a 4% high NaCl diet for 4 weeks or 11 weeks, the PGE, concentration doubles in both strains (p < 0.05) but the papillary PGE, concentration in the S rats is always about half that in the R rat (p < 0.01).Through effects on sodium (Na) excretion and papillary plasma flow, the low PGE, in S papillae may account in part for the large rises in the blood pressure (BP) of S rats after eating a high NaCI diet.This proposition was explored by utilizing high fat diets with either normal or high linoleic acid content.Arachidonic acid is the precursor of PGE, and linoleic add is the precursor of arachidonic acid.It turned out that the low PGE, level in S papillae could be tripled by a diet high in linoleic acid.Sixteen S rats on a 16-week diet of 5% NaCI and 1.5% linoleic acid had a mean papillary PGE, level of 30 compared to a level of 89 in 15 other S rats on a diet of 5% NaCI and 16% linoleic acid.The 16% high linoleic diet tripled the PGE, concentration in S papillae (p < 0.005).It also increased the PGE, concentration in R papillae Vh times, 137 vs 53 (p < 0.02).In rats on either high or normal linoleic diets, the PGE, In S papillae was always at least 35% less than that in R papillae.However, the 16% high linoleic diet did raise the papillary PGE, level In S rats up to that found in normal rats on regular rat chow of equivalent NaCI content.Moreover, this change in PGE, level was associated with greatly reduced BP rises in S rats.The BP of S rats on a 5% NaCI-1.5% linoleic diet began to rise after 5 weeks on the diet and reached 183 mm Hg after 16 weeks.The BP of S rats on a 5% NaCl-16% linoleic diet did not begin to rise until 12 weeks on the diet and reached only 166 after 16 weeks.The high linoleic diet greatly delayed the onset of the rise in BP and significantly reduced the ultimately attained level (p < 0.001).In fact, on a low 0.3% NaCI diet, S rats of comparable age reached approximately the same mildly hypertensive level of 166.Thus, in S rats, the high linoleic diet brings papillary PGE, up to normal and also prevents the large rises in BP usually related to a high NaCI Intake.These two changes may well be causally related.(Hypertension 4 (suppl II): II-149-II-153, 1982) KEY WORDS • sodium excretion • papillary plasma flow • prostaglandin E, • linoleic acid H UMAN essential hypertension clearly has a sodium aspect to it. 1Life-long low-salt diets can prevent hypertension even in susceptible individuals. 1' Diets very low in sodium can reduce the blood pressure (BP) in established hypertension.Drugs such as thiazides, which slightly reduce body Na content, can do the same.On the other hand, very high intakes of NaCI can raise BP in humans.*" 11The way in which Na affects the BP in humans is still not completely understood.To approach this question, we have made some observations in the two