The effect of salt loading on the urinary excretion of dopamine and sodium transport inhibitor in the rat

Effect of head-out water immersion on serum sodium transport inhibitor and urinary nonadrenaline excretion in pre-menopausal women

The effect of head out water immersion on the excretion of catecholamines and serum sodium transport inhibitor (STI) was studied in healthy young women during the follicular and leuteal phases. Two way ANOVA showed that menstrual cycle had no effect on the excretion of noradrenaline (NA), dopamine (DA) or serum STI. Analysis of pooled data from follicular and leuteal phases showed that immersion caused a significant increase in sodium excretion and serum STI and a significant decrease in urinary NA excretion in healthy young women. After immersion, sodium excretion, DA excretion and serum STI decreased and NA increased.

Effect of carbidopa on the excretion of sodium, dopamine, and ouabain-like substance in the rat

The effect of carbidopa, a competitive inhibitor of dopamine synthesis on the excretion of sodium, dopamine (DA), and endogenous sodium transport inhibitor (ESTI), was examined in rats on normal and high salt diets for 7 days. ESTI activity was measured (1) as ouabain-like substance (OLS) by radioimmunoassay using an antibody raised against ouabain, (2) by inhibition of purified Na+,K+-ATPase activity (ATPI), and (3) as digoxin-like substance (DLS) using a commercial digoxin assay. The OLS immunoassay was validated against rubidium transport studies. High salt diet caused an increase in OLS and ATPI but not DLS. Sodium excretion in rats on normal sodium intake was not affected by carbidopa treatment but was significantly lower in the high sodium diet group during the first 5 days of the study. In the low salt group, carbidopa treatment caused significant increases in OLS. We conclude that ESTI (measured as OLS) and DA are important in the natriuresis of salt loading.