Continuous Subcutaneous Administration of Miso Extracts Attenuates Salt-Induced Hypertension in Dahl Salt-Sensitive Rats

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.

Low Salt Diet in Pregnant Mothers Is Associated with Enhanced Salt Appetite in Their Offspring of Dahl Salt-Sensitive Rats

Objectives: We investigated an influence of salt intake during gestation or lactation in salt preference of weaning Dahl salt sensitive (Dahl S) strain. Material and Methods: Nine-week-old female Dahl S rats, after mated with the male, were divided into 1) high-salt group fed a 4% NaCl diet (high-salt mother) or 2) low-salt group fed a 0.3% NaCl diet (low-salt mother) during gestation or lactation periods. Using 0.4%, 0.6% and 0.8% (w/v) saline solutions, we assessed salt preference in their offspring after weaning. Systolic blood pressure (SBP) was determined by tail cuff method. Results: Both the male and female offspring from low-salt mothers during gestation consumed equal amounts of any saline solution. However, the amount of each saline solution was higher in the offspring of low-salt mothers than those of high-salt mothers. This resulted in a significant increase of salt intake in both the male and female offspring of low-salt mothers compared with those of high-salt mothers. In contrast, both the male and female offspring from low-mothers during lactation rather preferred the lower concentration of saline solution, and this resulted in less salt intake in the offspring of low-salt mothers than those of high-salt mothers. Conclusions: We demonstrated that low salt diet in pregnant mothers increased salt intake of their offspring. The offspring of mothers fed a low salt diet during lactation had less salt than those of high-salt mothers. The influence of salt intake of mothers in their offspring varies along with the growth stage of their babies.