Feeding but not salt loading is the dominant factor controlling urinary dopamine excretion in conscious rats

Mühlbauer, Bernd; Oßwald, Hartmut

doi:10.1007/bf00171092

Cited by 16 publications

(9 citation statements)

References 18 publications

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“…Therefore, most of the DA in urine comes from decarboxylation of L-DOPA in circulation but not from the renal excretion of circulating DA. [11,31,35] This could explain why the DA concentrations in the urine were not significantly higher in our fasting group than in the control group despite the statistically higher blood levels of DA in the fasting group. Similarly, M€ uhlbauer and Osswald [35] showed a remarkable increase in the renal DA excretion in fed compared to fasted animals.…”

Section: Resultscontrasting

confidence: 63%

Catecholamine levels in a Ramadan fasting model in rats: a case control study

Bucaktepe

Akdağ

Daşdağ

et al. 2016

Biotechnology & Biotechnological Equipment

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Eating habits as well as physical exercise are very important for a healthy lifespan. Ramadan-type fasting, which is food and water avoidance during the daylight period for four weeks, has drawn attention due to its positive impacts on metabolism and health. The aim of this study was to compare the blood and urine catecholamine (CA) levels in fasting and non-fasting rats, in terms of stress response. A total of 20 male rats were randomly divided into a fasting group and a control group. Four weeks later, blood and urine samples were taken after decapitation. Analysis of CAs was done using high-performance liquid chromatography with florescence detection (HPLC-FLD). The dopamine (DA), adrenaline (ADR) and noradrenaline (NA) blood and urine concentrations were found to be higher in the fasting group compared to the control group, but the difference was statistically significant only for the blood DA levels (p < 0.05). In the fasting group, the blood values of ADR and NA correlated with each other but not with the DA levels, whereas there was correlation among the urine levels of DA, ADR and NA. In the control group, the blood and urine values of DA, ADR and NA correlated with each other. The differences observed in the blood and urine CAs indicate a specific regulation of CAs in Ramadan-type fasting, which needs to be investigated thoroughly in future studies.

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Section: Resultscontrasting

confidence: 63%

Catecholamine levels in a Ramadan fasting model in rats: a case control study

Bucaktepe

Akdağ

Daşdağ

et al. 2016

Biotechnology & Biotechnological Equipment

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“…In a study in conscious rats, Isaac et al [22] report ed changes in urinary dopamine excretion due to phosphate content of the chow. Very re cently, experiments in our laboratory demon strated the dominant role of feeding in the control of renal dopamine production [23]. It might lie possible that inhibition of peripheral dopamine synthesis contributes to changes in thirst and salt appetite.…”

Section: Discussionmentioning

confidence: 97%

Urinary Dopamine Excretion in Conscious Rats: Effect of Carbidopa in Different States of Sodium Balance

Mühlbauer

Oßwald²

1993

Kidney Blood Press Res

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Urinary dopamine excretion was studied in seven different groups of rats (n = 6-12) with the following treatment regimens: normal chow and tap water (controls, CON), single administration of furosemide 20 mg/kg i.p. on day 1 and subsequent feeding of low sodium chow (low salt, LS), normal chow and 1 % NaCl as drinking water (high salt HS) normal chow and 1% NaCl plus deoxycorticosterone acetate 1 mg/kg/day i.p. (high salt plus DOCA, HS+DOCA); carbidopa 20 mg/kg/day p.o. (CDP) was administered in animals on normal chow (CON+CDP), in high salt rats (HS+ CDP), andinratsonhighsaltplusDOCA(HS+DOCA+CDP).Onday5, rats were placed in metabolic cages with free access to their respective drinking solution; chow was withheld. Urine was collected for 24 h and analyzed for sodium, creatinine, and dopamine. Urinary dopamine excretion rates did not change in proportion to large differences in sodium excretion in LS, HS, and HS+DOCA animals compared to CON. Only when urinary dopamine excretion of HS rats was compared to the LS group there was a moderate but significant increase of 27%. In the groups treated with CDP renal dopamine excretion was decreased by approximately 60% in comparison to the groups with the respective treatment condition but without CDP. Urinary sodium output was unchanged by CDP in CON+ CDP animals compared to CON. In HS+CDP and HS+DOCA+CDP groups renal sodium excretion was reduced by half compared to the HS and HS+DOCA groups, respectively. However, this effect was accompanied by a similar, approximately 55% reduction of oral volume and sodium intake. Renal sodium excretory capacity was unchanged by CDP treatment. Daily sodium balance (intake minus output) was similar in all experimental groups. We conclude that (1) changes in urinary sodium output during CDP treatment could be caused by extrarenal factors, and (2) sodium balance should be controlled in experiments on renal dopamine production in conscious animals. The results do not support the concept that endogenous dopamine is a crucial factor in the renal response to oral sodium load in conscious rats.

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“…However, the regulation of intrarenal dopamine synthesis is not completely understood. Enhanced urinary dopamine excretion has been observed after feeding and systemic protein load in man and rat (Williams et al 1986;Kaufman et al 1989;Mühlbauer and Osswald 1992). The presence of the catecholamine precursors L-tyrosine and L-phenylalanine in the chow was identified as being crucial for the increase in urinary dopamine in response to feeding in rats (Mühlbauer et al 1997).…”

Section: Introductionmentioning

confidence: 91%

Renal response to infusion of dopamine precursors in anaesthetized rats

Mühlbauer¹,

Gleiter²,

Gies³

et al. 1997

Naunyn-Schmiedeberg's Arch Pharmacol

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In the present study the renal response to intravenous infusion of the catecholamine precursors L-dihydroxyphenylalanine (L-DOPA) or L-tyrosine was investigated in thiopentone sodium-anaesthetized Sprague-Dawley rats. Glomerular filtration rate (GFR) was assessed by renal clearance of inulin, urinary concentration of dopamine (U(DA)V) by HPLC and sodium excretion (U(Na)V) by flame photometry. We found that basal U(DA)V was 6.5 +/- 0.5 pmol/min per 100 g body weight (mean +/- SEM). Intravenous infusion of L-tyrosine at 0. 1-3.0 micromol/min dose dependently enhanced U(DA)V (17 +/- 3 to 144 +/- 14 pmol/min respectively) with higher doses of L-tyrosine resulting in no further increase in U(DA)V. Compared with L-tyrosine administration significantly lower doses of L-DOPA (0.07 to 35 nmol/min) caused increases in U(DA)V which were orders of magnitude higher (18 +/- 1 to 7800 +/- 470 pmol/min, respectively) and did not show saturation characteristics. GFR did not change in response to L-tyrosine or L-DOPA infusion. No variations in urinary flow rate or in U(Na)V could be observed which were significantly correlated to changes in U(DA)V. In contrast, intravenous infusion of dopamine at a dose of 6 nmol/min significantly increased GFR by 35 +/- 6.2% and urinary flow rate by over 2-fold. Immunohistochemistry with light microscopy revealed no tyrosine hydroxylase in the kidney. Therefore, dopamine synthesis in the tubular cells mainly depends on the renal supply of L-DOPA. The unchanged GFR and U(Na)V in spite of large variations of U(DA)V argue against the hypothesis that intratubular dopamine plays a functional role in the regulation of hemodynamics or sodium transport in the kidney. Renal dopamine excretion may rather represent an effective pathway for the elimination of catecholamine precursors from the plasma.

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Feeding but not salt loading is the dominant factor controlling urinary dopamine excretion in conscious rats

Cited by 16 publications

References 18 publications

Catecholamine levels in a Ramadan fasting model in rats: a case control study

Catecholamine levels in a Ramadan fasting model in rats: a case control study

Urinary Dopamine Excretion in Conscious Rats: Effect of Carbidopa in Different States of Sodium Balance

Renal response to infusion of dopamine precursors in anaesthetized rats

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