UMLS:C0035078 - FACTA Search

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Query: UMLS:C0035078 (renal failure)
31,970 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The renal functional changes following infusion of dopamine are well documented. The most pronounced effect is the increase in renal blood flow and a marked natriuretic response. Due to its specific renal effects, dopamine has become one of the most frequently used drugs in the treatment of critically ill patients with low cardiac output states and/or acute oliguric renal failure. Pharmacological effects of dopamine are dose dependent. Low doses of dopamine predominantly stimulate dopaminergic receptors, but with increasing doses actions secondary to stimulation of adrenergic beta(1) and alpha receptors also appear. Dopamine receptors are classified into the D1 and the D2 subtype families. Stimulation of D1 receptors increases adenylate cyclase activity and intracellular levels of cAMP, whereas D2 receptor activation decrease or do not change adenylate cyclase activity. In the kidney, dopamine receptors have been localized in the renal vasculature except in glomeruli and in the tubules (the proximal tubule > macula densa > the loop of Henle > the distal tubule > collecting ducts). The postsynaptic D1 receptor mediates vasodilation by a direct mechanism, whereas the presynaptic D2 receptor indirectly may dilate the vessels by inhibition of norepinephrine release. Consistent with previous results in animals, the present haemodynamic studies revealed that dopamine in normal subjects elicits a dose dependent biphasic effect on the mean arterial blood pressure. With 1 and 2 micrograms/kg/min, a depressor effect resulted from a decrease in the diastolic pressure, whereas a pressor effect, seen with doses at and above 7.5 micrograms/kg/min, was mainly caused by elevations of the systolic pressure. The studies indicated that the increase in cardiac output at low doses of dopamine is secondary to a decrease in peripheral vascular resistance, independent of effects of beta(1) receptors on cardiac contractility and heart rate. Dose-response studies demonstrated that the dopamine-induced increase in effective renal plasma flow (ERPF) reaches its maximum at 3 micrograms/kg/min. The increase in ERPF remained unchanged by pretreatment with metoprolol, and a comparison of dopamine and dobutamine in doses producing similar increases in cardiac output demonstrated that only dopamine increased ERPF. These findings indicate that indirect haemodynamic effects secondary to increases in cardiac contractility and cardiac output do not contribute significantly to the increase in renal perfusion caused by dopamine. In normal subjects, acute hypoxaemia attenuated the renal vasodilating effect of dopamine. The well known natriuretic effect of dopamine was significantly expressed in all of our studies, in which doses ranging from 1 to 5 micrograms/kg/min caused about a two-fold increase in sodium excretion. At doses at and above 7.5 micrograms/kg/min which increased mean arterial pressure, dopamine further increased sodium clearance (CNa) while ERPF was decreasing, indicating the contribution of pressure natriuresis at these high doses. Although not affecting the percentage increase in CNa, metoprolol suppressed the absolute, maximal response to non-pressor doses of dopamine, suggesting that a reduced adrenergic beta(1) receptor activity may indirectly affect the natriuretic response, probably by decreasing renal perfusion pressure. Previous studies in animals demonstrated that dopamine natriuresis can occur independent of increases in ERPF and GFR, and, furthermore, that the response can be abolished by specific D1 receptor antagonists. Evidence obtained by in vitro studies indicated that dopamine via D1 receptors may inhibit the Na(+)-H+ antiport at the brush-border membrane of proximal tubular cells and the Na(+)-K(+)-ATPase activity at basolateral membranes of both the proximal tubule and the medullary thick ascending limb of the loop of Henle. (ABSTRACT TRUNCATED)
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PMID:Effects of dopamine on renal haemodynamics tubular function and sodium excretion in normal humans. 967 40

The ability to control body hydration is frequently impaired with age. This mainly results from changes in thirst and from loss of renal concentrating ability. The cellular mechanisms responsible for this functional renal failure have been extensively studied in different experimental models. Although the loss of nephrons sometimes observed with age impairs the ability of the kidney to retain water, a similar defect was reported in animals free of glomerulosclerosis, indicating that the reduction in the number of nephrons was not the only cause. Because age-related polyuria has also been demonstrated in rats with unchanged secretion of vasopressin, renal changes in water reabsorption was hypothesized. Such alterations have been searched along the whole length of the nephron. Neither the single nephron filtration rate nor proximal or early distal flow rates were modified in senescent animals where water reabsorption in the collecting duct was reduced. The affinity and the density of the V2 receptors were mainly constant in most experimental models of ageing. In contrast, intracellular cAMP accumulation following vasopressin stimulation was reduced in the oldest animals. The expression of aquaporins in luminal and basolateral membranes of the collecting duct epithelial cells was altered. The amount of basolateral aquaporin 3 and 4 was respectively decreased by 50 per cent and unchanged in renal papilla. In addition, the expression of aquaporin 2, which is rate limiting for the osmotic permeability of the collecting duct, was reduced by 50 per cent in the outer medulla and by 80 per cent in the inner medulla of the senescent animals. This drop in aquaporin 2 expression in the distal part of the nephron could be the main cause for the fall in concentrating ability of the kidney and the age-related impaired control of hydration.
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PMID:[Kidney aging: cellular mechanisms of problems of hydration equilibrium]. 1021 38

The human CLC-5 chloride channel is expressed mainly in the kidney and its mutations cause Dent's disease (a familial renal tubular syndrome with hypercalciuria, tubular proteinuria, rickets, nephrocalcinosis, and eventual renal failure). To gain insight into the regulatory mechanism of CLC-5 expression, a genomic clone that contains the 5'-flanking region of the human CLC-5 gene was isolated and characterized. Two types of 5'-ends of cDNA were isolated by 5'-rapid amplification of cDNA ends, and one of them, approximately 2.1 kbp upstream of ATG-containing exon II, was first identified in human. The major promoter activity was detected in the 5'-flanking region of this newly identified exon Ia. The sequence of the proximal 5'-flanking region contained an activator protein (AP)-1-like site and cAMP-responsive element, but it lacked a TATA box, a GC-rich element, and an SP-1 site. Deletion analysis of the 5'-flanking region showed that the fragments containing the AP-1-like element (TGACTCC) positioned at -38 exhibited high promoter activities in CLC-5 expressing LLC-PK1 cells, but that further deletions not containing this AP-1-like element resulted in a great loss of luciferase activities. Gel-retardation analysis demonstrated the existence of a specific protein binding to this AP-1-like element in LLC-PK1 cells, which seemed to differ from an authentic AP-1. This study clarified the key element of the human CLCN5 promoter, and the mutation in this region could be the cause of Dent's disease.
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PMID:Isolation and characterization of the human CLC-5 chloride channel gene promoter. 1116 24

Hypertension is a major risk factor for heart attacks, stroke, and kidney failure. It is estimated to cause as many as 25% of all deaths in the United States, particularly for African Americans, in whom the disease is both more common and more severe. Essential hypertension is a multifactorial disorder influenced by both genetic and environmental factors. Physiological studies have shown that the kidneys play an important role in the maintenance of sodium balance, extracellular fluid volume, and long-term control of blood pressure. The sodium transporters in the kidney affect the amount of sodium and water reabsorption in the nephron and thus control extracellular fluid volume and blood pressure. Of the renal sodium transporters, the amiloride-sensitive epithelial sodium channels (ENaC), which are responsible for the rate-limiting step of sodium reabsorption in the distal nephron, are therefore important candidates in the development of hypertension. Moreover, mutations in this channel have been shown to cause a rare form of heritable hypertension (Liddle's syndrome), and genetic linkage studies show that the beta- and gamma-subunits are linked to systolic blood pressure. Several polymorphisms have been identified in the beta- and gamma-subunits of this channel, of which the beta-T594M variant is of particular interest. This variant is found in individuals of African American descent and not in Caucasians and may be associated with hypertension in some populations of African descent. Lymphocytes from individuals with this variant channel show an increased sodium conductance in response to cAMP in vitro. Studying the polymorphic variants in the various subunits of ENaC may further our understanding of the mechanisms that underlie sodium balance in mammals. These variants will provide an avenue to identify molecular targets for new diagnostic and therapeutic tools in the clinical treatment of hypertension.
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PMID:Epithelial sodium channels and hypertension. 1125 50

The present study was performed to examine whether the gentamicin-induced urinary concentration defect is related to an altered regulation of aquaporin (AQP) water channels in the kidney. Male Sprague-Dawley rats were subcutaneously injected with gentamicin (20, 50 or 100 mg/kg per day) for 6 days. The protein expression of AQP1-3 channels and the catalytic activity of adenylyl cyclase were determined in the kidney. Gentamicin treatment resulted in renal failure associated with decreased tubular free water reabsorption and increased urinary flow rate. The expression of AQP2 proteins was significantly decreased in the kidney, in which the cortex was most susceptible, followed by the outer medulla and inner medulla in order. Gentamicin treatment also decreased the shuttling of AQP2, as evidenced by a decrease of its expression in the membrane fraction in proportion to that in the cytoplasmic fraction. The protein expression of AQP1 as well as that of AQP3 was also decreased in the cortex by treatment with the highest dose of gentamicin. The cAMP generation in response to arginine vasopressin or sodium fluoride was decreased by gentamicin, while that to forskolin was not significantly altered. These findings suggest that the primary impairment in the pathway leading to the generation of cAMP lies at the level of G proteins, resulting in a decreased expression of cAMP-mediated AQP channels. The gentamicin-induced urinary concentration defect may in part be accounted for by a reduced abundance of AQP water channels in the kidney.
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PMID:Gentamicin decreases the abundance of aquaporin water channels in rat kidney. 1138 43

The present study was intended to examine whether the amphotericin-induced urinary concentration defect can be related to an altered regulation of aquaporin (AQP) water channels in the kidney. Male Sprague-Dawley rats were injected with amphotericin B (6 mg/kg/d, IP ) for 21 days. The protein expression of AQP1-3, Gsalpha, and adenylyl cyclase was determined in the kidney. To further specify the primary point of dysregulation of AQP channels that are activated by the arginine vasopressin/cyclic adenosine monophosphate (AVP/cAMP) pathway, different components of adenylyl cyclase complex were separately examined for their cAMP-generating activities. Amphotericin treatment resulted in kidney failure associated with decreased tubular water reabsorption and increased urinary flow rate. The expression of AQP2 proteins was significantly decreased in the outer medulla and inner medulla but not in the cortex. The expression of AQP2 proteins in the membrane fraction changed in parallel with that in the cytoplasmic fraction, suggesting a preserved targeting. Neither the expression of AQP1 nor that of AQP3 was significantly affected in the cortex, outer medulla, or inner medulla. The cAMP generation in response to AVP or sodium fluoride was decreased, whereas that to forskolin was not significantly altered. The expression of Gsalpha proteins was decreased in the inner medulla, whereas that of adenylyl cyclase VI remained unaltered. These findings indicate that the amphotericin-induced urinary concentration defect may in part be causally related to a reduced abundance of AQP2 channels in the kidney. It is also suggested that the primary impairment in the pathway leading to the activation of AQP channels that are regulated by the AVP/cAMP pathway lies at the level of G proteins.
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PMID:Amphotericin B decreases adenylyl cyclase activity and aquaporin-2 expression in rat kidney. 1157 18

A 93 year-old woman was admitted due to anorexia and unconsciousness. Biochemical examination of serum showed hypercalcemia (corrected Ca; 16.6 mg/dl). The level of intact parathyroid hormone (i-PTH) was suppressed, whereas parathyroid hormone-related peptide (PTHrp) was to 5.0 pM (normal range: below 0.6 pM). IL-6 and renal cAMP were also elevated. We started to ameliorate hypercalcemia by saline infusion, furosemide and calcitonin. However, hypercalcemia was not improved and the patient died of DIC and renal failure. Autopsy revealed primary lesion of NHL (diffuse large B cell type) to be in the stomach with infiltration of lymphoma into the liver, pancreas, spleen, adrenal glands, jejunum, and lumbar vertebrae. The results of immunohistochemical examination demonstrated the expression of PTHrP in lymphoma cells. PTHrP was also found in lymphoma cells of the spleen by the RT-PCR technique. These findings indicated that hypercalcemia was caused by overexpression of PTHrP from lymphoma cells.
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PMID:[An elderly case of non-Hodgkin's lymphoma (NHL) with hypercalcemia]. 1270 52

The polycystic kidney diseases (PKDs) are a group of genetic disorders causing significant renal failure and death in children and adults. There are no effective treatments. Two childhood forms, autosomal recessive PKD (ARPKD) and nephronophthisis (NPH), are characterized by collecting-duct cysts. We used animal models orthologous to the human disorders to test whether a vasopressin V2 receptor (VPV2R) antagonist, OPC31260, would be effective against early or established disease. Adenosine-3',5'-cyclic monophosphate (cAMP) has a major role in cystogenesis, and the VPV2R is the major cAMP agonist in the collecting duct. OPC31260 administration lowered renal cAMP, inhibited disease development and either halted progression or caused regression of established disease. These results indicate that OPC31260 may be an effective treatment for these disorders and that clinical trials should be considered.
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PMID:Inhibition of renal cystic disease development and progression by a vasopressin V2 receptor antagonist. 1450 83

To determine if radiocontrast impairs vascular relaxation of the renal artery, segments (4-5 mm in length) of canine renal artery were suspended in vitro in organ chambers to measure isometric force (95% O2/5% CO2, at 37 C). Arterial segments with and without endothelium were placed at the optimal point of their length-tension relation and incubated with 10 microM indomethacin to prevent synthesis of endogenous prostanoids. The presence of nonionic radiocontrast (iohexol, Omnipaque 350, 1 ml in 25 ml control solution, 4% (v/v)) did not alter endothelium-dependent relaxation to acetylcholine in rings precontracted with both norepinephrine and prostaglandin F2alpha (N = 6). When the rings were precontracted with prostaglandin F2alpha, the presence of ionic contrast did not inhibit the relaxation of the arteries. However, in canine renal arteries contracted with norepinephrine, the presence of ionic radiocontrast (diatrizoate meglumine and diatrizoate sodium, MD-76, 1 ml in 25 ml control solution, 4% (v/v)) inhibited relaxation in response to acetylcholine, sodium nitroprusside (N = 6 in each group), and isoproterenol (N = 5; P < 0.05). Rings were relaxed less than 50% of norepinephrine contraction. Following removal of the contrast, vascular relaxation in response to the agonists returned to normal. These results indicate that ionic radiocontrast nonspecifically inhibits vasodilation (both cAMP-mediated and cGMP-mediated) of canine renal arteries contracted with norepinephrine. This reversible impairment of vasodilation could inhibit normal renal perfusion and act as a mechanism of renal failure following radiocontrast infusion. In the adopted experimental protocol the isoproterenol-induced relaxation of renal arteries precontracted with norepinephrine was more affected, suggesting a pivotal role of the cAMP system.
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PMID:Ionic radiocontrast inhibits endothelium-dependent vasodilation of the canine renal artery in vitro: possible mechanism of renal failure following contrast medium infusion. 1476 82

Recent investigations of parathyroid hormone (PTH) have advanced our understanding of its circulating forms as well as its action. It is now clear that first-generation immunoradiometric assays of so-called intact "PTH" not only measured full-length PTH(1-84) but also recognized large PTH fragments lacking the amino-terminus. New, second generation assays detect only full-length PTH. Under diverse pathological settings, second generation assays display lower levels of PTH (1-84). By measuring full-length PTH (bioactive PTH) and the combined full-length plus amino-terminal PTH fragments, the amount of non-PTH(1-84) in circulation can be estimated. The primary amino-terminal fragment is likely to be PTH(7-84). A considerable controversy surrounds the pathological significance of PTH(7-84) and its relation to adynamic bone disease. While these findings were emerging, other work uncovered the apparent basis by which PTH receptors signal through cAMP in some instances but through Ca/inositol phosphate in others. This signaling switch is dictated by the cytoplasmic adapter protein NHERF1 (EBP50), which is expressed in a cell-selective fashion. Other provocative findings may provide a means of unifying determinations of PTH(7-84) with the effects of NHERF1 on PTH receptor signaling. These latter studies reveal that in cells expressing NHERF1, PTH(7-84) has no effect on PTH receptor signaling or internalization. However, in cells lacking or expressing low levels of NHERF1, PTH(7-84) internalizes the PTH receptor without accompanying activation. Together, these findings suggest that the accumulation of PTH(7-84) in renal failure may lead to PTH resistance by internalizing and down-regulating PTH receptors.
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PMID:PTH revisited. 1546 96

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