Abstract
Objective: Long-term intake of Miso attenuates hypertension in Dahl salt-sensitive (Dahl S) rats through an increased urinary sodium excretion. We examined whether a bolus injection into the peritoneal cavity (i.p.) or a continuous subcutaneous infusion of a Miso extract attenuates hypertension in Dahl S rats. Materials and Methods: We investigated the effects of a bolus, i.p. injection of 50 mg Miso extract in 0.5 mL on hypertension in Dahl S rats, and examined whether a long-term subcutaneous infusion of the Miso extract (50 mg Miso/day), using an osmotic mini-pump working for 14 days, attenuates hypertension in Dahl S rats. Results: A bolus, i.p. injection of 50 mg Miso extract decreased SBP in 2 hrs. The reduction was significant at 4 hrs, and SBP returned to the baseline at 24 hrs. The SBP reduction at 4 hrs after the injection was increasingly greater each day during the 4 days. The SBP reduction by the Miso extract was dose-dependent and the antihy-pertensive activity occurs in a <5 kDa fraction of the extract. The subcutaneous infusion of 50 mg Miso extract/day for 14 days significantly attenuated hypertension in Dahl S rats. The SBP reduction was associated with significant decreases in the heart and kidney weights. Urinary protein excretion significantly decreased in the Miso group. The SBP reduction was not associated with increases in either urinary sodium excretion or fractional excretion of sodium. Conclusions: SBP reduction by very low-dose of the Miso extract may be mediated partly by mechanisms other than renal sodium handling.
Highlights
Miso is a traditional Japanese food that was originally described in Taiho Ritsurei in 701 AD
We and investigators from other laboratory have reported in the previous study that long-term intake of Miso soup or Miso attenuates development of salt-induced hypertension in Dahl saltsensitive (Dahl S) rats when compared with rats given the same amount of saline solutions as the salt contents in Miso soup [1]-[3]
We examined the long-term effects of the low-dose (50 mg/day) Miso extract on systolic blood pressure (SBP) in Dahl S rats with salt-induced hypertension using a continuous, osmotic mini-pump working for 14 days
Summary
Miso is a traditional Japanese food that was originally described in Taiho Ritsurei in 701 AD. One serving of Miso soup generally contains 1 - 1.5 g salt which supports the long-standing belief that traditional Miso soup is to blame for the high incidence of salt-sensitive hypertension and subsequent cerebral stroke in Japan. We and investigators from other laboratory have reported in the previous study that long-term intake of Miso soup or Miso attenuates development of salt-induced hypertension in Dahl saltsensitive (Dahl S) rats when compared with rats given the same amount of saline solutions as the salt contents in Miso soup [1]-[3]. The reduction in blood pressure in the Miso group corresponds to approximately 30% reduction in salt intake. Miso inhibits salt absorption in the intestine. The constituent(s) of Miso soup increase urinary excretions of sodium, thereby decreasing salt loading. The functions of Miso constituents are similar to vasodilators
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