Dahl salt-sensitive rats develop hypovitaminosis D and hyperparathyroidism when fed a standard diet

High dietary cholecalciferol increases plasma 25-hydroxycholecalciferol concentration, but does not attenuate the hypertension of Dahl salt-sensitive rats fed a high salt diet

“…We demonstrated that loss of protein-bound vitamin D metabolites into urine is a primary cause of hypovitaminosis D when salt-sensitive rats are fed a high salt diet [8,9]. We report here that high dietary cholecalciferol increased plasma 25-OHD 3 concentrations of young Dahl salt-sensitive rats fed 3% salt.…”

“…We identified both 25-OHD and 25-OHD binding activity in the urine of Dahl S rats [8,9] and concluded that protein-bound vitamin D metabolites were lost into the urine. The urine was shown to have primarily albumin and also vitamin D binding protein (DBP).…”

“…Urine was tested for specific binding to 25-OHD 3 by previously published methods [8,9]. Urine samples were diluted with 0.1 M boric acid buffer, pH 8.6, containing γ-globulin.…”

“…Salt sensitivity and hypertension are more prevalent in the African-American population than in the Caucasian-American population [15,16]. Thierry-Palmer et al [8,9] have suggested that low vitamin D status in saltsensitive individuals may result from loss of vitamin D metabolites into urine, in addition to low dietary intake and/or decreased skin synthesis. Studies indicate that salt intake in the USA is high [17,18] and can be as much as three times the recommended maximum of 100 mmol/ d [18].…”

“…A high salt diet, however, had no significant effect on blood pressure or plasma 25-OHD concentration of young salt-resistant rats. The low plasma 25-OHD concentrations of salt-sensitive rats during high salt intake were demonstrated to be caused in large part by loss of protein-bound 25-OHD into urine [8,9].…”