Male stroke-prone spontaneously hypertensive rats (SHRSP) were fed 4% NaCI diets containing either 0.75% normal K or 2.11% high K, starting at 6 weeks of age. After 8 months on these diets, 40 out of 58 SHRSP on 0.75% K had died (69% mortality), vs. 2 dead out of 95 on 2.11% K (2% mortality), a 97% reduction in mortality (p < 0.00001). After 20 weeks on the diets, the daytime and nighttime BPs of each rat were measured intra-arterially under light ether. Using these accurate measures of blood pressure (BP), we selected two groups precisely matched for BP. One matched SHRSP group (BP, 182) ate the 0.75% K diet and 30 out of 47 rats died (64% mortality). The other matched SHRSP group (BP, 182) ate the 2.11% K diet and 2 out of 35 died (6% mortality), a 91 % reduction of mortality (p < 0.0001). Seemingly, the striking reduction in mortality rate with the 2.11% high-K diet does not depend on a lowering of BP. High-K diets do not change muscle, aorta, or body Na or K. Dry weight of mesenteric arterioles was reduced 29% on the 2.11% K diet vs. the 0.75% K diet (5.43 mg vs. 7.66 mg; p < 0.0001), indicating a greatly reduced hypertensive hypertrophy, even though BP was equal in the two groups compared. Aortic wall wet weight was reduced 25.5% in 36 rats on a 2.11% K diet vs. 26 rats on a 0.75% K diet (36.7 mg vs. 49.2 mg; p < 0.001), even though BP was equal in the two groups compared. In 9 surviving SHRSP on 0.75% K, 13 of 36 brain hemisphere slides (4 slides per rat) showed infarcts (36%). In 11 surviving SHRSP on 2.11% K, 1 of 44 brain slides showed infarcts (2%), a 95% reduction (p < 0.0001). In other SHRSP on a 0.75% diet for 8 weeks, 18 of 25 rats (72%) had spots of brain hemorrhage, whereas only 2 of 36 rats (5.5%) 011 2.11% K had similar hemorrhages, a 92% reduction (p < 0.00001). High-K diets allow cerebral arteries to carry very high BPs without sustaining damage to the artery wall, thereby drastically reducing brain hemorrhages and infarcts, and lowering the death rate. Moreover, hypertension does not invariably lead to artery hypertrophy, since a high-K diet can prevent most of it.
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