A decreased tubular uptake of dopa results in defective renal dopamine production in aged rats

Armando, Inés; Nowicki, Susana; Aguirre, J.; Barontini, Marta

doi:10.1152/ajprenal.1995.268.6.f1087

Cited by 26 publications

(45 citation statements)

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“…Also, the age of the animals in the 2 studies was different, in that although we used 6-and 24-month-old rats, the previous study used 3-and 12-month-old rats. 17 Unlike the findings of an increase in urinary dopamine excretion during HS intake in Fischer 344 adult rats, in our previous study in Wistar rats placed on an HS intake, we did not see a significant increase in urinary excretion of dopamine. 25 We believe this discrepancy is related to the strain of animal used, as we have repeatedly failed to observe this type of an effect of an increase in urinary dopamine when Wistar rats are placed on an HS intake (M.A.V.-C., unpublished observation, 1999).…”

Section: Discussioncontrasting

confidence: 99%

“…Our present findings of a similar urinary excretion of dopamine and DOPAC in adult and old rats are at variance with a previous report showing that urinary dopamine and DOPAC excretion values were lower in old than adult rats. 17 This discrepancy may be due to differences in the strain of rats; ie, we used Fischer 344 animals, whereas Armando et al 17 used Wistar rats. Also, the age of the animals in the 2 studies was different, in that although we used 6-and 24-month-old rats, the previous study used 3-and 12-month-old rats.…”

Section: Discussionmentioning

confidence: 94%

“…Also, old Wistar rats had a reduced ability to take up L-DOPA into tubular cells, similar to findings of another group of investigators. 17 Again, these discrepancies are most likely due to the different strains of animal used in the different studies. It is also interesting to note that although we were able to detect basal levels of DOPAC in the present study in Fischer 344 rats, we were unable to detect basal DOPAC levels in Wistar rats, 18 which may be due to the fact that basal DOPAC levels in Wistar rats are beyond the limit of detection of our assay procedure.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, several groups have shown an association between renal delivery of sodium and the ability to form dopamine, 26,27 and in vitro studies have shown that L-DOPA uptake by renal epithelial cells is a sodium-dependent process. 17,28,29 If the uptake of L-DOPA by tubular epithelial cells in old rats became defective, then it would not be able to respond to an increase in sodium by synthesizing more dopamine.…”

Section: Discussionmentioning

confidence: 99%

“…11 High blood pressure or edema formation may be linked to abnormalities in the function of the renal dopaminergic system, such as decreased ability to synthesize dopamine 12,13 and deficient coupling of dopamine receptors to effector mechanisms. 6,14 -16 Despite their normal blood pressure, an increasing number of studies have revealed that old rats may present particular deficiencies in the renal handling of L-DOPA, its subsequent conversion to dopamine, 17,18 and at the level of receptor number or coupling to G proteins. 19 -21 Recently, 24-month-old Fischer 344 rats were reported to have an impairment in dopamine receptor-mediated inhibition of renal Na ϩ ,K ϩ -ATPase.…”

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confidence: 99%

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Aging, High Salt Intake, and Renal Dopaminergic Activity in Fischer 344 Rats

et al. 1999

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Abstract-The present study examined renal dopaminergic activity and its response to high salt (HS) intake in adult (6-month-old) and old (24-month-old) Fischer 344 rats. Daily urinary excretion of L-3,4-dihydroxyphenylalanine (L-DOPA), dopamine, and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid was similar in adult and old rats; by contrast, daily urinary excretion of norepinephrine in old rats was almost twice that in adult animals. HS intake (1% NaCl) over a period of 24 hours resulted in a 2-fold increase in the urinary excretion of dopamine, DOPAC, and norepinephrine in adult animals but not in old animals. Norepinephrine and L-DOPA plasma levels did not change during HS intake and were similar in both groups of rats. The natriuretic response to an HS intake in old rats (from 4.7Ϯ0.4 to 10.) was less than in adult rats (from 5.2Ϯ0.4 to 13.5Ϯ2.5 nmol ⅐ kg. A diuretic response to HS intake was observed in adult rats (from 20.9Ϯ2.3 to 37.6Ϯ2.8 mL ⅐ kg Ϫ1 ⅐ d Ϫ1 ) but not in old rats (from 37.7Ϯ5.7 to 42.3Ϯ6.0 mL ⅐ kg). Dopamine levels and dopamine/L-DOPA ratios in the renal cortex of old rats were greater than in adult rats. HS intake increased both dopamine levels and dopamine/L-DOPA ratios in the renal cortex of adult rats but not in old rats. Aromatic L-amino acid decarboxylase activity was higher in old rats than in adult rats; HS intake increased L-amino acid decarboxylase activity (nmol ⅐ mg protein Ϫ1 ⅐ l5 min Ϫ1 ) in adult rats (from 67Ϯ1 to 93Ϯ1) but not in old rats (from 86Ϯ2 to 87Ϯ2). Dopamine inhibited Na ϩ ,K ϩ -ATPase activity in proximal tubules obtained from adult rats, but it failed to exert such an inhibitory effect in old rats. It is concluded that renal dopaminergic tonus in old rats is higher than in adult rats but fails to respond to HS intake as observed in adult rats. This may be due in part to the inability of dopamine to inhibit Na ϩ ,K ϩ -ATPase activity in old rats. (Hypertension. 1999;34:666-672.)

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Aging, High Salt Intake, and Renal Dopaminergic Activity in Fischer 344 Rats

et al. 1999

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Dopamine and Renal Function and Blood Pressure Regulation

Armando

Villar

José

2011

Comprehensive Physiology

105

215

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Dopamine is an important regulator of systemic blood pressure via multiple mechanisms. It affects fluid and electrolyte balance by its actions on renal hemodynamics and epithelial ion and water transport and by regulation of hormones and humoral agents. The kidney synthesizes dopamine from circulating or filtered L-DOPA independently from innervation. The major determinants of the renal tubular synthesis/release of dopamine are probably sodium intake and intracellular sodium. Dopamine exerts its actions via two families of cell surface receptors, D1-like receptors comprising D1R and D5R, and D2-like receptors comprising D2R, D3R, and D4R, and by interactions with other G protein-coupled receptors. D1-like receptors are linked to vasodilation, while the effect of D2-like receptors on the vasculature is variable and probably dependent upon the state of nerve activity. Dopamine secreted into the tubular lumen acts mainly via D1-like receptors in an autocrine/paracrine manner to regulate ion transport in the proximal and distal nephron. These effects are mediated mainly by tubular mechanisms and augmented by hemodynamic mechanisms. The natriuretic effect of D1-like receptors is caused by inhibition of ion transport in the apical and basolateral membranes. D2-like receptors participate in the inhibition of ion transport during conditions of euvolemia and moderate volume expansion. Dopamine also controls ion transport and blood pressure by regulating the production of reactive oxygen species and the inflammatory response. Essential hypertension is associated with abnormalities in dopamine production, receptor number, and/or posttranslational modification.

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Overexpression of Na+/K+-ATPase Parallels the Increase in Sodium Transport and Potassium Recycling in an In Vitro Model of Proximal Tubule Cellular Ageing

2006

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Na(+)/K(+)-ATPase plays a key role in the transport of Na(+) throughout the nephron, but ageing appears to be accompanied by changes in the regulation and localization of the pump. In the present study, we examined the effect of in vitro cell ageing on the transport of Na(+) and K(+) ions in opossum kidney (OK) cells in culture. Cells were aged by repeated passing, and Na(+)/K(+)-ATPase activity and K(+) conductance were evaluated using electrophysiological methods. Na(+)K(+)-ATPase alpha(1)- and beta(1)-subunit expression was quantified by Western blot techniques. Na(+)/H(+) exchanger activity, changes in membrane potential, cell viability, hydrogen peroxide production and cellular proliferation were determined using fluorimetric assays. In vitro cell ageing is accompanied by an increase in transepithelial Na(+) transport, which results from an increase in the number of Na(+)/K(+)-ATPase alpha(1)- and beta(1)-subunits, in the membrane. Increases in Na(+)/K(+)-ATPase activity were accompanied by increases in K(+) conductance as a result of functional coupling between Na(+)/K(+)-ATPase and basolateral K(+) channels. Cell depolarization induced by both KCl and ouabain was more pronounced in aged cells. No changes in Na(+)/H(+) exchanger activity were observed. H(2)O(2) production was increased in aged cells, but exposure for 5 days to 1 and 10 microM: of H(2)O(2) had no effect on Na(+)/K(+)-ATPase expression. Ouabain (100 nM: ) increased alpha(1)-subunit, but not beta(1)-subunit, Na(+)/K(+)-ATPase expression in aged cells only. These cells constitute an interesting model for the study of renal epithelial cell ageing.

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A decreased tubular uptake of dopa results in defective renal dopamine production in aged rats

Cited by 26 publications

References 0 publications

Aging, High Salt Intake, and Renal Dopaminergic Activity in Fischer 344 Rats

Aging, High Salt Intake, and Renal Dopaminergic Activity in Fischer 344 Rats

Dopamine and Renal Function and Blood Pressure Regulation

Overexpression of Na+/K+-ATPase Parallels the Increase in Sodium Transport and Potassium Recycling in an In Vitro Model of Proximal Tubule Cellular Ageing

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