The effect of salt loading on the urinary excretion of dopamine and sodium transport inhibitor in the rat.
1. The temporal relationship between the excretion of dopamine and sodium transport inhibitor (STI) during salt loading was examined in the rat. 2. Urine samples were collected before and during salt loading (given as 18 g/l NaCl solution to replace drinking water) for the measurement of sodium, creatinine, dopamine and STI in 6 female rats. Dopamine was measured by HPLC and STI was extracted and measured by its ability to inhibit purified Na+, K(+)-ATPase enzyme. 3. Urinary sodium and STI (expressed in relation to creatinine) on day 1 of salt loading were 4.6 and 4.2 times respectively of the control values. Urinary excretion of dopamine did not increase significantly until day 2 when it was 21% higher. 4. The excretion of STI paralleled that of sodium excretion whereas the excretion of dopamine lagged behind. 5. We conclude that salt loading increases STI and dopamine and that the increase in STI precedes that of dopamine.
Ho
C S
CS
Department of Chemical Pathology, Prince of Wales Hospital, Shatin, NT, Hong Kong.
Fung
S L
SL
Swaminathan
R
R
D000818:Animals; D001693:Biological Transport, Active; D004298:Dopamine / Q000652:urine*; D005260:Female; D009318:Natriuresis; D010455:Peptides / Q000652:urine*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors
D010455:Peptides; C029311:serum sodium transport inhibitor; D012965:Sodium Chloride; D004298:Dopamine