Effects of extracellular fluid volume changes on renal response to low‐dose dopamine infusion in normal women

Abstract

Dopamine (DA) i.v. infused in a low dose (0.1 microgram/kg/min) in healthy women during sustained hypotonic polyuria, produced different renal functional effects as variations in extracellular fluid volume occurred. (1) In hydro-saline retention (n = 23), induced by desoxycorticosterone acetate treatment, DA produced typical vasodilator and hydro-natriuretic effects (Goldberg, 1972). (2) In hydro-saline depletion (n = 19), induced by diuretic treatment and low dietary sodium intake, DA lost its vasodilator and natriuretic efficacy, manifesting, on the other hand, renal sodium conserving effects mainly dependent on the increase in distal sodium reabsorption and a trend towards afferent arteriolar vasoconstriction. (3) Treatment with prazosin (n = 9) or propranolol (n = 9) in hydro-saline depletion, was efficacious in partly restoring the typical vasodilator and natriuretic effects of DA. Thus, in hydro-saline depletion, DA produced sympathomimetic effects which were sufficiently intense to outweigh those due to activation of specific DA renal receptors.

Blunted renal dopaminergic system activity in HgCl2-induced membranous nephropathy

“…This suggestion fits well with the finding that the decrease in urinary dopamine output in HgCl 2 -treated rats preceded the decrease in urinary sodium excretion as well as with the finding that the reduction in proximal tubular AADC activity was more pronounced during the phase of greatest sodium retention (day 14) than during either day 7 or day 21. Because the natriuresis resulting from the inhibitory effect of tubular transport by dopamine is mainly evident in volumeexpanded states but not in sodium-depleted states (Agnoli et al, 1987;Ragsdale et al, 1990) we decided to evaluate the significance of the lack of renal dopamine in HgCl 2 -treated rats during an acute volume expansion, in conditions of greatest sodium retention and ascites accumulation (day 14). Since it is generally agreed that the natriuretic effects of dopamine are mainly mediated by D 1 -like receptors (Baines et al, 1992;Chen and Lokhandwala, 1993;Narkar et al, 2002;Felder et al, 1993), we decided to evaluate the proximal tubular Na + ,K + -ATPase activity during volume expansion and the effects of the D 1 -like agonist fenoldopam on both proximal sodium transport and urinary sodium excretion.…”

“…Since the natriuretic effect of dopamine is evident in euvolemic and volume-expanded states but not in sodium-depleted states (Agnoli et al, 1987;Ragsdale et al, 1990), the experiments were performed during an acute VE with saline. The urinary sodium excretion before (t = 0 -120 min), during (t = 120-150 min) and after (t = 150-240 min) VE with isotonic saline in HgCl 2 -treated and control rats on day 14 is depicted in Fig.…”

The Renin-Angiotensin and Renal Dopaminergic Systems Interact in Normotensive Humans

“…We confirm previous reports of natriuresis with D 1 -like receptor stimulation in normotensive humans on normal 49 and HS 22 diets, but not on LS diets. 22,46,47 In our cohort of salt-resistant normotensive humans, decreased mean BP in response to fenoldopam alone occurred on HS but not LS diets. When enalapril was added to fenoldopam, the mean BP decreased on both diets, suggesting that the RAAS could have mitigated the BP-lowering effect of fenoldopam during salt restriction.…”

“…[18][19][20][21][22][24][25][26]31,32,34,39 The natriuretic effect of dopamine is impaired in salt-depleted states. 46,47 We submit evidence, for the first time in normotensive (,120/80 mmHg) 48 salt-resistant humans, 33 that the RAS and dopaminergic system interact in regulating renal sodium transport on LS and HS diets. We confirm previous reports of natriuresis with D 1 -like receptor stimulation in normotensive humans on normal 49 and HS 22 diets, but not on LS diets.…”

Antagonistic Effects of Sulpiride – Racemic and Enantiomers – on Renal Response to Low-Dose Dopamine Infusion in Normal Women

“…On the basis of our previous observa tions in humans, the renal effects of DA infused at a low rate depend on hydrosaline balance and, probably, on the renal sympathetic activity level [Agnoli et al, 1978]. Indeed the typical DA renal effects, present in hydrosaiine retention, are suppressed in the presence of a moder ate hydrosaline depletion; however, in the latter condi tion the pretreatment with either ¿//-propranolol or pra zosin partly restored the typical DA renal effects [Agnoli et al, 1987],…”