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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to assess the effects of the calcium entry blocker nicardipine and alpha human atrial natriuretic peptide (hANP) on antihypertensive and diuretic activity in hypertensive surgical patients. The site of the diuretic actions of these drugs along the nephron were also investigated by measuring the excretion rate of inorganic phosphate (PO4). Hypertension during gastrectomy was treated by increasing the concentration of enflurane, by nicardipine infusion (0.5-2.0 micrograms.kg-1 x min-1), or by hANP infusion (0.05-0.2 microgram.kg-1 x min-1) under general anaesthesia. Enflurane, nicardipine and hANP all decreased arterial pressure to the same extent. Urine flow, Na and PO4 excretion increased following the administration of nicardipine or hANP. Fractional distal reabsorption of sodium was suppressed from 89.7 +/- 2.8% to 82.1 +/- 5.0% by the hANP, but not by the nicardipine infusion. Creatinine clearance was increased by hANP infusion, but did not change in the nicardipine group. It is concluded that nicardipine and hANP can be used safely for the treatment of hypertension during surgery. Both drugs induced phosphaturic diuresis, but the site of action of the two drugs on the nephron may be different. Phosphate reabsorption is considered to occur largely in the renal proximal tubule, so that its appearance in the urine in increased quantities without the change of renal circulation in the nicardipine group suggests a proximal tubular action of this drug. However, the site of action of hANP in the kidney was not determined because GFR increased and distal sodium reabsorption was suppressed due to the drug infusion.
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PMID:Treatment of intraoperative hypertension with enflurane, nicardipine, or human atrial natriuretic peptide: haemodynamic and renal effects. 145 Dec 21

The offspring of essential hypertensive parents have been found to exhibit abnormalities in renal hemodynamics and sodium handling before the eventual occurrence of hypertension. The reported abnormalities represent a wide spectrum of changes including increased GFR, normal or decreased RPF, slight increase in blood pressure (although within the normal range), and an exaggerated natriuresis response to a sodium load. The heterogeneity of these abnormalities may reflect the specific conditions of the studies, the lability of the changes, or different subgroups of subjects with genetic predisposition to essential hypertension. Several lines of evidence have suggested a relationship between hypertension and the development of diabetic nephropathy in insulin-dependent diabetics. This laboratory has found that recent-onset insulin-dependent diabetics can exhibit renal hemodynamics abnormalities very early in the course of diabetes according to a positive or negative family history of essential hypertension. These changes include increased GFR and mean arterial pressure, but no differences in renal sodium and lithium handling in diabetics with a genetic predisposition to essential hypertension. In addition, diabetics with a positive family history of essential hypertension exhibited a more-marked vasodilative response to an acute interruption of the renin-angiotensin system, further suggesting inadequate angiotensin modulation of renal vascular tone. The significance of these abnormalities in relation to the development of diabetic nephropathy requires further investigation.
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PMID:Predisposition to essential hypertension and renal hemodynamics in recent-onset insulin-dependent diabetic patients. 145 59

A placebo-controlled, double-blind clinical trial has been initiated to determine whether angiotensin-converting enzyme inhibitor (ACEI) therapy with captopril (25 mg three times daily) slows the progressive loss of renal function in patients with type 1 diabetes mellitus. Entry criteria include; (1) ages 18 to 50 yr; (2) onset of insulin-dependent diabetes before the age of 30 yr, insulin dependent for at least 7 yr; (3) 24-h urine protein excretion > 500 mg, plus: (a) diabetic retinopathy or (b) if no retinopathy, a renal biopsy diagnosis of diabetic nephropathy; (4) serum creatinine (SCr) < 2.5 mg/dL; (5) informed consent. Patients follow strict medical management protocols. Systemic blood pressure is controlled to predefined goals (< 140-90 mm Hg). The primary outcome of the Study is a doubling of the patients' entry SCr to at least 2 mg/dL confirmed by a > 50% decrease in GFR by radioactive iothalamate clearance technique. Baseline characteristics of the cohort at entry into the Study are (mean +/- SD): male/female, 52%/48%; age, 35 +/- 8 yr; duration of diabetes, 21 +/- 7 yr; duration of proteinuria, 2.8 +/- 3.3 yr; duration of retinopathy, 4.5 +/- 4.1 yr; 50% of cohort presented with hypertension, duration, 4 +/- 4.7 yr; blood pressure, 139/86 +/- 19/12; SCr, 1.35 +/- 0.44 mg/dL; GFR 78 +/- 32 mL/min; BUN, 24 +/- 11 mg/dL; proteinuria, 3.1 +/- 3.3 g/day; cholesterol, 236 +/- 50 mg/dL; total glycosylated hemoglobin, 11.1 +/- 2.1%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A controlled clinical trial of angiotensin-converting enzyme inhibition in type I diabetic nephropathy: study design and patient characteristics. The Collaborative Study Group. 145 67

The effects of dietary (10% calories) safflower (SAF), evening primrose (EPO), and fish oil (F) as sources of linoleic acid (control), gamma-linolenic acid, and long-chain n-3 fatty acids, respectively, on cardiovascular and renal responses to chronic (5 weeks) cyclosporine administration were studied in male borderline hypertensive rats. In one experiment (n = 9/group), oral administration of CsA at 0.1 mg/kg.day significantly increased awake systolic blood pressure vs. placebo in SAF-fed rats (P less than 0.01). This increase was prevented by both EPO (P less than 0.001) and F (P less than 0.01), in the absence of group differences in body weight gain or plasma electrolyte levels. In a second experiment, CsA also increased blood pressure vs. placebo in SAF-fed rats (P less than 0.001). While this increase was prevented by EPO (P less than 0.001), F had no significant effect. Differences in group blood pressure responses were not explained by group differences in body weight gain or trough levels of blood CsA. Renal function, assessed in anesthetized rats after week 5, demonstrated a CsA-related (10 mg/kg.day) decrease in whole-kidney GFR in SAF-fed animals vs. placebo (P less than 0.05) that was prevented by EPO and attenuated by F. EPO and F also tended to reduce the CsA-induced elevation in renovascular resistance, but this difference did not reach statistical significance. These findings suggest the potential of dietary EPO and F to offset nephrotoxic effects of CsA administration, and suggest that EPO may also be useful in countering CsA-induced hypertension.
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PMID:Attenuation of cyclosporine-induced hypertension by dietary fatty acids in the borderline hypertensive rat. 154 60

Renal pathological changes of diabetes include thickening of all renal extracellular basement membranes and the mesangial matrix and, to a lesser extent, mesangial cell expansion. Two renal lesions appear critical in diabetic nephropathy. Mesangial expansion out of proportion to the size of the glomerulus is related to proteinuria, hypertension, and declining GFR. Arteriolar hyalinosis is related to global glomerulosclerosis, and both are correlated with the clinical features of nephropathy. By the time renal dysfunction is clinically detectable, these lesions tend to be advanced. Interstitial volume may be increased in insulin-dependent diabetes mellitus, particularly in areas containing sclerotic glomeruli or marked tubular atrophy. Parallel findings were documented for type I membranoproliferative glomerulonephritis in which the increased mesangial volume fraction was related to decreased GFR, increased glomerular permeability to protein, and hypertension. As in diabetes, the cortical interstitial volume fraction is correlated with functional abnormalities in type I membranoproliferative glomerulonephritis. Thus, in both of these chronic glomerular disorders, mesangial expansion and interstitial expansion are associated with disordered renal function. Thus, it is not true that glomerular structural changes correlate poorly with glomerular function. Whether it is the glomerular or interstitial pathology or both that is causally responsible for the dysfunction requires further study.
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PMID:Renal structure and function in insulin-dependent diabetes mellitus and type I membranoproliferative glomerulonephritis in humans. 160 Jan 34

Tubuloglomerular feedback (TGF) is an important intrarenal regulatory mechanism, which acts to stabilize renal blood flow, GFR, and the tubular flow rate. The anatomical basis for this negative feedback system is the Juxtaglomerular Apparatus (JGA). This is located at the point of contact between the thick ascending limb of the loop of Henle (TAL) and the vascular pole of the glomerulus. The JGA includes the macula densa, a specialized plaque of cells in the TAL thought to be responsible for the sensing step in the feedback mechanism; the mesangial cells, a cushion of cells separating the macula densa from the vascular pole of the glomerulus; and the afferent arteriole, the main effector site for the TGF. An increase in the NaCl concentration at the macula densa elicits a response in the smooth muscle cells of the afferent arteriole increasing the hemodynamic resistance of the preglomerular vasculature. These changes will, through decreases in the GFR and the tubular flow rate, cause a decrease in the NaCl concentration at the macula densa. Thus, the system acts to stabilize the NaCl concentration at the macula densa. The purpose of the present study was to describe the dynamic characteristics of the TGF, and to use this knowledge in elucidating the role of the TGF system in the autoregulation of renal blood flow. Further, by comparing the dynamic characteristics of TGF between hypertensive and normotensive rats, to identify possible alterations in renal function that could play a role in the etiology and pathogenesis of hypertension. Anesthesia and surgery are unavoidable complications in experimental work in animals. It is shown that the anesthetics commonly used in micropuncture experiments in rats have different effects on various aspects of renal function, e.g. GFR, sodium excretion, proximal tubular compliance, and TGF function. It is concluded that the thiobarbiturate inactin, the most used anesthetic, has more detrimental effects on renal function than halothane and other barbiturates. In halothane anesthetized rats, the proximal tubular pressure oscillates with a frequency of 30-50 mHz. The pressure oscillations are associated with oscillations in tubular flow, and the early distal tubular Cl- activity. The possible mechanisms behind the oscillations are discussed. It is concluded that the oscillations appear because of the operation of the TGF system. Although it seems unlikely, it cannot be excluded that a vascular pacemaker is involved in the underlying oscillatory mechanism. To test the hypothesis that the oscillations are caused by the TGF system, a series of dynamic mathematical models of the TGF system have been developed.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Dynamic aspects of the tubuloglomerular feedback mechanism. 161 20

Glomerular hemodynamics were measured in male Sprague-Dawley rats, aged 4 to 5 months (young) or 20 to 22 months (old). Body weight (BW) and left kidney weights (KW) were higher in old rats than young (BW: 507 +/- 12 g v 342 +/- 11 g, P less than 0.001; KW: 2.0 +/- 0.1 g v 1.3 +/- 0.1 g, P less than 0.001). Arterial blood pressure (AP) was slightly higher in old rats, but within the normotensive range (106 +/- 4 mm Hg v 94 +/- 4 mm Hg, P less than 0.05). Glomerular filtration rate (GFR; factored for KW) was lower in old versus young rats (0.67 +/- 0.05 mL/min/gKW v 1.00 +/- 0.08 mL/min/gKW, P less than 0.02). The cortical surface of the kidney in old (but not young) rats showed marked heterogeneity and single-nephron (SN)GFR was measured only in filtering nephrons and was higher and more variable in old versus young rats. Glomerular blood pressure (PGC) was unchanged in old compared with young rats (53 +/- 4 mm Hg v 55 +/- 2 mm Hg). There was a significantly greater level of glomerular sclerosis (in outer cortical glomeruli) in old versus young rats, and glomerular volume was substantially greater in old rats. This study suggests that age-related glomerulopathy is not primarily mediated by glomerular capillary hypertension.
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PMID:The effect of aging on glomerular hemodynamics in the rat. 162 81

These studies, using in vivo micropuncture techniques in the Munich-Wistar rat, document the magnitude of changes in glomerular and tubular function and structure 24 h after approximately 75% nephron loss (Nx) and compared these results with those obtained in sham-operated rats. The contribution of either nephron hypertrophy or renal prostaglandin to these adjustments in nephron function was also explored. After acute Nx, single nephron GFR (SNGFR) was increased, on average by approximately 30%, due primarily to glomerular hyperperfusion and hypertension. The approximately 45% reduction in preglomerular and the constancy in postglomerular vascular resistances was entirely responsible for these adaptations. Although increases in fluid reabsorption in proximal convoluted tubules correlated closely with increase in SNGFR, the fractional fluid reabsorption between late proximal and early distal tubular segments was depressed. Nephron hypertrophy could not be substantiated based on either measurements of protein content in renal tissue homogenates or morphometric analysis of proximal convoluted tubules. However, acute Nx was associated with increased urinary excretory rates per functional nephron for 6-keto-PGF1 alpha and TXB2. Prostaglandin synthesis inhibition did not affect function in control nephrons, but this maneuver was associated with normalization of glomerular and tubular function in remnant nephrons. The results suggest that enhanced synthesis of cyclooxygenase-dependent products is one of the earliest responses to Nx, and even before hypertrophy the pathophysiologic effects of prostaglandin may be important contributors to the adaptations in remnant nephron function.
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PMID:Glomerular and tubular adaptive responses to acute nephron loss in the rat. Effect of prostaglandin synthesis inhibition. 169 76

The renal impairments were studied clinicopathologically in 57 patients with progressive systemic sclerosis (scleroderma). Proteinuria, hematuria, azotemia and hypertension, used as markers for renal involvements, were observed in 3 (5.3%), 4 (7.0%), 2 (3.5%) and 6 patients (10.5%) respectively, at the initial examination. Hypertension was increased 2.6 times at the last observation, although the incidence of other three markers have not changed during the follow-up period. Finally, 17 out of 57 patients (29.8) revealed more than one of these clinical markers throughout the study. The decrease of GFR (CThio) was noticed in 3 out of 36 cases (8.3%), however that of RPF (CPAH) in 11 of 36 patients (30.6%), including 5 without abnormal clinical markers. Histological studies were performed in 12 patients. One showed crescentic glomerulonephritis, two membranous nephropathy, and the remaining 9 minor glomerular abnormalities. On the other hand, the vascular changes such as intimal proliferation of interlobular arteries were frequently observed. The frequency of pulmonary involvements, skin ulcer and gastro-intestinal involvement in the patients with renal lesions were not significantly different from that of the non-renal group. The level of RPF was significantly lower in the patients with skin ulcer than that of those without skin ulcer. No significant difference was noticed in the frequency of renal involvements between the patients with or without anti-Scl-70 antibody.
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PMID:[Clinicopathological studies of renal disorders in patients with progressive systemic sclerosis]. 174 19

In 191 patients with mesangial IgA nephropathy, GFR was determined as clearance of 51Cr-EDTA. 86 (45%) of them had subnormal renal function 7.3 +/- 4.6 years after renal biopsy. The change in GFR was followed in 153 patients with repeated determinations of 51Cr-EDTA clearance. 50.3% of the patients had a loss of more than 1.1 ml/min/year, which we regard as pathological. The markers of progressive disease were: male sex, high output of urinary protein, severe histological lesions and presence of hypertension. Even patients lacking these markers had a significantly increased incidence of progressive disease. Of 93 patients, with initially normal GFR, 32% will have a subnormal GFR within five years and 25% will develop end-stage renal failure within 20 years. In 38 patients with six or more determinations of 51Cr-EDTA clearance, the predictive value of the first four determinations was calculated. Of 26 with a decrease of more than 1.1 ml/min/year, 13 (50%) developed subnormal GFR during follow-up, while 11 of 12 (91.7%) with a decrease of less than 1.1 ml/min/year (P less than 0.05) remained normal. This shows that repeated determinations of GFR with an accurate method will predict the final outcome early in the disease. We also confirmed that single or repeated determinations of clearance of creatinine are of little value in separating a normal GFR from a slightly decreased one, but more reliable in detecting a markedly reduced GFR.
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PMID:Deterioration of GFR in IgA nephropathy as measured by 51Cr-EDTA clearance. 176 5


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