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Query: UMLS:C0085580 (essential hypertension)
 14,686 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In conclusion, a complete RAS is present in the mammalian proximal tubule that is potentially autocrine and paracrine in nature. Maneuvers that stimulate renin in JG cells and renal vasculature appear to also stimulate renin in the proximal tubule. The subcellular localization of the different components and the regulation of this epithelial RAS still remain to be defined. This RAS may be important in regulation of proximal tubule NaCl and NaHCO3 transport. Finally, one can speculate that activation of this RAS may play a pathogenetic role in some patients with essential hypertension and in the hypertension and cyst growth seen in autosomal dominant polycystic kidney disease.
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PMID:The renal proximal tubule renin-angiotensin system. 827 88

So far, two isoforms of the neutral Na+K+-2Cl- cotransporter have been cloned in mammals. One isoform, BSC1, mediates apical ion entry in the renal thick ascending limb of Henle and a second, BSC2, appears to be an ubiquitously expressed Na+K+-2Cl- cotransporter. In primary cultures of rabbit proximal tubule, porcine aortic endothelial cells, and rat vascular smooth muscle cells, expression of the second isoform BSC2 was demonstrated by Northern blot analysis and bumetanide-sensitive 86Rb+ uptake studies. A surprising finding was the absence of BSC2 in fully differentiated freshly-isolated proximal tubule, porcine aortic endothelial cells, and rat vascular smooth muscle cells. Several studies have reported modulation of Na+K+-2Cl- cotransport activity by vasoactive substances and suggested a role for disturbed cotransport in, for example, the pathogenesis of essential hypertension. All these observations, however, were made in cultured cells which, in view of our findings, makes the physiological relevance questionable.
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PMID:Culturing induced expression of basolateral Na+-K+-2Cl- cotransporter BSC2 in proximal tubule, aortic endothelium, and vascular smooth muscle. 858 42

In order to evaluate tubular damage in diabetic patients, the activity of renal proximal tubule derived enzymes excreted in 24-hour urine were recorded in 5 groups as follows: (i) 48 noninsulin-independent diabetic patients with normal renal function and a urinary albumin excretion rate within the normal range; (ii) 45 noninsulin-dependent diabetic patients with normal renal function and a high urinary albumin level; (iii) 26 noninsulin-dependent diabetic patients with renal failure; (iv) 40 patients with essential hypertension and normal renal function, and (v) 48 normal control subjects. Regardless of whether cases were noninsulin-dependent diabetics with normal or high urinary albumin excretion rate or cases with renal dysfunction, urinary dipeptidyl aminopeptidase IV and N-acetyl-beta-D-glucosaminidase excretions were significantly higher than in healthy subjects, and urinary gamma-glutamyl transpeptidase excretion was significantly lower than in healthy subjects. No significant changes in urinary enzyme excretions showed specific variations in the essential hypertensive patients. These results suggest that there is tubular damage in the early stages of noninsulin-dependent diabetic patients with normal renal function and normal urinary albumin excretion rate. Detection of urinary excretion of dipeptidyl aminopeptidase IV, N-acetyl-beta-D-glucosaminidase and gamma-glutamyl transpeptidase may be especially useful for the early diagnosis of diabetic nephropathy.
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PMID:Diagnostic significance of urinary enzymes for diabetes mellitus and hypertension. 858 4

We review some of the effects that insulin exerts on glomerular and tubular functions. In healthy subjects, insulin has little or no effect on renal hemodynamics, glomerular filtration rate, or permeability to albumin. In patients with noninsulin-dependent diabetes, hyperinsulinemia selectively increases urinary albumin excretion. In vivo, euglycemic hyperinsulinemia is associated with reduced urinary sodium excretion both under conditions of forced and normal diuresis. Whether the principal site of this action is the proximal or distal tubule remains somewhat controversial. The effect, however, is not mediated by insulin-induced hypokalemia and antikaliuresis, as it is still observed when plasma potassium concentrations and urinary potassium excretion are maintained. Hyperglycemia potentiates insulin antinatriuresis through an effect on the proximal tubule (sodium-glucose cotransport). Insulin antinatriuresis is accompanied by a reduction in the urinary excretion of uric acid. Both the antinatriuretic and antiuricosuric effect of insulin are preserved in states of insulin resistance of glucose metabolism (obesity, diabetes, essential hypertension). Thus, in insulin resistant individuals compensatory hyperinsulinemia imposes a chronic antinatriuretic and antiuricosuric pressure on the kidney. This may provide an explantation for the clustering of insulin resistance with hypertension and hyperuricemia.
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PMID:Renal effects of insulin in man. 937 25

The ability of the dopamine-1 (D1)-like receptor to stimulate adenylyl cyclase (AC) and phospholipase C (PLC), inhibit sodium transport in the renal proximal tubule (RPT), and produce natriuresis is attenuated in several rat models of hypertension. Since the inhibitory effect of D1-like receptors on RPT sodium transport is also reduced in some patients with essential hypertension, we measured D1-like receptor coupling to AC and PLC in cultures of human RPT cells from normotensive (NT) and hypertensive (HT) subjects. Basal cAMP concentrations were the same in NT (n=6) and HT (n=4). However, the D1-like receptor agonist fenoldopam increased cAMP production to a greater extent in NT (maximum response=67+/-1%) than in HT (maximum response=17+/-5%), with a potency ratio of 105. Dopamine also increased cAMP production to a greater extent in NT (32+/-3%) than in HT (14+/-3%). The fenoldopam-mediated increase in cAMP production was blocked by SCH23390 (a D1-like receptor antagonist) and by antisense D1 oligonucleotides in both HT and NT, indicating action at the D1 receptor. The stimulatory effects of forskolin and parathyroid hormone-related protein of cAMP accumulation were not statistically different in NT and HT, indicating receptor specificity and an intact G-protein/AC pathway. The fenoldopam-stimulated PLC activity was not impaired in HT, and the primary sequence and expression of the D1 receptor were the same in NT and HT. However, D1 receptor serine phosphorylation in the basal state was greater in HT than in NT and was not responsive to fenoldopam stimulation in HT. These studies demonstrate the expression of D1 receptors in human RPT cells in culture. The uncoupling of the D1 receptor in both rats (previously described) and humans (described here) suggests that this mechanism may be involved in the pathogenesis of hypertension; the uncoupling may be due to ligand-independent phosphorylation of the D1 receptor in hypertension.
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PMID:Dopamine-1 receptor coupling defect in renal proximal tubule cells in hypertension. 1020 44

Dopamine modulates cardiovascular function by actions in the central and peripheral nervous system, by altering the secretion/release of prolactin, pro-opiomelanocortin, vasopressin, aldosterone, and renin, and by directly affecting renal function. Dopamine produced by the renal proximal tubule exerts an autocrine/paracrine action via two classes of dopamine receptors, D1-like (D1 and D5) and D2-like (D2, D3, and D4), that are differentially expressed along the nephron. The autocrine/paracrine function of dopamine, manifested by tubular rather than by haemodynamic mechanisms, becomes most evident during extracellular fluid volume expansion. This renal autocrine/paracrine function is lost in essential hypertension and in some animal models of genetic hypertension. The molecular basis for the dopaminergic dysfunction in hypertension may involve an abnormal post-translational modification of dopamine receptors.
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PMID:D1 dopamine receptor signalling defect in spontaneous hypertension. 1069 8

Renal sodium re-absorption is a closely regulated process serving to maintain both extracellular fluid volume and arterial blood pressure. Proteins participating in sodium re-absorption and its regulation are therefore important candidate proteins whose genes may contain sequence variation contributing to the inherited tendency for increased arterial blood pressure (essential hypertension). Important insight has come from rare forms of single-gene hypertension in human subjects and from polygenic animal models of genetic hypertension. Both indicate the primacy of altered renal function in the genesis of hypertension, and suggest that genes contributing to the disease are members of the subset of genes expressed in the kidney. This review examines evidence for abnormalities in renal sodium re-absorption in hypertension and focuses on the proximal tubule as a site of relevant dysfunction. Identification of the proteins participating in renal sodium re-absorption and its regulation, particularly those involved in the renal pressure-natriuresis mechanism, will allow gene cloning and sequencing which in turn may lead to the identification of novel gene sequence variation participating in hypertension.
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PMID:Renal proximal tubule sodium transport and genetic mechanisms of essential hypertension. 1082 52

A number of studies have shown that hyperuricaemia is associated with an increased incidence of coronary heart disease. It has been proposed that the elevated serum uric acid levels are linked to other risk factors, such as hypertension, dyslipidaemia and diabetes. Hyperuricaemia is commonly encountered in patients with essential hypertension and is considered as a risk factor for morbidity and mortality associated with hypertension. In addition, lipid abnormalities (mainly hypertriglyceridaemia) are also found more frequently in hypertensive patients than in normotensives. There is evidence that the angiotensin II receptor antagonist, losartan, increases urate excretion by reducing reabsorption of urate in the renal proximal tubule. It is also known that fibric acid derivatives (fibrates) have several beneficial actions in addition to their lipid-lowering capacity. Fenofibrate administration is associated with a uric acid lowering effect. In this respect, we present two patients with hypertension and dyslipidaemia together with elevated serum uric acid levels. We also discuss (in the format of questions and answers) the pathophysiological mechanisms underlying the association of serum uric acid with cardiovascular disease, and we review the relevant literature to justify an evidence-based decision to choose an antihypetensive agent (losartan) or a lipid-lowering drug (fenofibrate) with an additional hypouricaemic effect.
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PMID:Management of hypertension and dyslipidaemia in patients presenting with hyperuricaemia: case histories. 1119 Oct 5

All of the components of a complete dopamine system are present within the kidney, where dopamine acts as a paracrine substance in the control of sodium excretion. Dopamine receptors can be divided into D(1)-like (D(1) and D(5)) receptors that stimulate adenylyl cyclase and D(2)-like (D(2), D(3), and D(4)) receptors that inhibit adenylyl cyclase. All 5 receptor subtypes are expressed in the kidney, albeit in low copy. Dopamine is synthesized extraneuronally in proximal tubule cells, exported from these cells largely into the tubule lumen, and interacts with D(1)-like receptors to inhibit the Na(+)-H(+) exchanger and Na(+),K(+)-ATPase, decreasing tubule sodium reabsorption. During moderate sodium surfeit, dopamine tone at D(1)-like receptors accounts for approximately 50% of sodium excretion. In experimental and human hypertension, 2 renal dopaminergic defects have been described: (1) decreased renal generation of dopamine and (2) a D(1) receptor-G protein coupling defect. Both defects lead to renal sodium retention, and each may play an important role in the pathophysiology of essential hypertension.
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PMID:Theodore Cooper Lecture: Renal dopamine system: paracrine regulator of sodium homeostasis and blood pressure. 1156 94

The purpose of this study was to evaluate the association of the insulin resistance syndrome with both blood pressure and target organ damage in blacks and whites with essential hypertension. Eighty-two black and 63 white French Canadian patients were studied. None had diabetes, and antihypertensive medications had been discontinued for >/=1 week. Measurements included 24-hour blood pressure monitoring, fasting plasma lipids, insulin sensitivity determined with the Bergman minimal model, echocardiogram, microalbumin excretion, and inulin and lithium clearances. Compared with the white French Canadians, black patients had an attenuated nighttime reduction in blood pressure (P<0.02), increased cardiac dimensions (P<0.001), greater microalbumin excretion (P<0.05), increased inulin clearance (indicative of glomerular hyperfiltration; P<0.001), and decreased lithium clearance (indicative of increased sodium reabsorption in the proximal tubule; P<0.001). Blood pressure levels were not related to insulin resistance; although in blacks, the nighttime reduction in systolic blood pressure was inversely related to fasting plasma insulin (r=-0.18, P<0.04). In a stepwise multivariate analysis (including blood pressure levels and components of the insulin resistance syndrome as independent variables), race was the strongest predictor of left ventricular mass (r=0.53, P<0.000), relative wall thickness (r=0.49, P<0.000), and both inulin (r=0.53, P<0.000) and lithium (r=0.41, P<0.000) clearances. Nighttime systolic blood pressure was also a significant determinant of concentric left ventricular hypertrophy (r=0.37, P<0.000). In blacks, microalbumin excretion was related to insulin resistance. These observations are consistent with the hypothesis that there is a genetic contribution to cardiac hypertrophy, glomerular hyperfiltration, and sodium retention in blacks with essential hypertension.
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PMID:Predictors of target organ damage in hypertensive blacks and whites. 1164 Dec 83


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