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Biomedical subjects

V M Buckalew

Publications and source records attributed to V M Buckalew.

At least 19 recordsLinked to original sources
PubMed1994

Pathophysiology of progressive renal failure.

Progressive renal failure is conditioned by a number of factors, including type of renal disease, sex, level of arterial pressure, insulin deficiency and/or hyperglycemia in diabetes mellitus, and dietary protein intake. Elevated arterial pressure may cause a progressive renal disease, hypertensive nephrosclerosis, and accelerate the rate of progression of all other chronic renal disease. Hypertension contributes to progressive renal failure by inducing myointimal hyperplasia of arcuate and afferent arterioles, causing glomerular ischemia, and by increasing pressure in the glomerular capillaries. The latter leads to hyperfiltration of protein, increased mesangial ingestion of protein, and glomerular sclerosis. Increased glomerular pressure may also be induced by protein feeding, insulin deficiency and hyperglycemia, especially in the presence of reduced nephron number. Thus at least one common mechanism underlies the effect of hypertension, protein feeding, and diabetes on the progression of chronic renal disease.

Humans↗
PubMed1994

End-stage renal disease: can dietary protein restriction prevent it?

The hypothesis that dietary protein restriction slows the rate of progression of chronic renal disease has been tested in four large clinical trials, the largest and most elegant of which was the Modification of Diet in Renal Disease (MDRD) study conducted recently in the United States. During these trials the majority of patients with nondiabetic renal disease had slow progression, and no overall benefit from dietary intervention was demonstrated in three of four studies. However, MDRD is the first trial to suggest that protein restriction has a two-stage effect on renal function. During the first 4 months, glomerular filtration rate (GFR) fell more rapidly in patients with protein restriction than in patients with normal protein intake, probably because of a hemodynamic effect on the renal microcirculation. After this 4-month period, the rate of decline in GFR was slower in patients on the low protein diet. This suggests but does not prove that low protein diet may slow progression of renal disease in the long run. MDRD also showed that strict control of hypertension slows progression in patients with heavy proteinuria.

Dietary Proteins↗
PubMed1993

Effects of phospholipids on renal function.

The effects of two classes of phospholipids (PL) on renal function have been studied. Bolus injections of 1 ng (10 pmol) of lysophosphatidylcholine (LPC) caused natriuresis and diuresis in rats. Natriuretic activity was eliminated by substituting unsaturated bonds in the 1-acyl group and by removing the choline group on the sn-3 position. Natriuretic activity was not affected by substitution of 1-alkyl for 1-acyl groups. In the dog, LPC was natriuretic when given as a bolus of 3.0 micrograms/kg or as a constant infusion at 5 ng/kg/min. To explore further the effect of alkyl PLs on renal function, a series of studies with platelet activating factor (PAF) was performed. PAF injected directly into the renal artery (IR) in bolus doses of 0.5-10 ng/kg caused renal vasodilation that was blocked by a specific PAF receptor antagonist. This effect was not due to release of vasodilatory eicosanoids, dopamine, or nitric oxide (NO). PAF given IR as a continuous infusion at 2.5 ng/kg/min attenuated the renal vasoconstrictor effects of angiotensin II and norepinephrine but not vasopressin. This effect to attenuate vasoconstriction was blocked by the NO inhibitor N-monomethyl-L-arginine. These studies using picomolar amounts of PL suggest a physiologic role for these compounds in control of renal function.

Angiotensin II↗
PubMed1992

Effect of lysophosphatidylcholine on renal hemodynamics and excretory function in anesthetized rats.

The effect of myristoyl-lysophosphatidylcholine (myristoyl-LPC) on renal hemodynamics, electrolyte and water excretion was examined over a 90 min period in sodium pentobarbital anesthetized male Sprague Dawley rats. Intravenous infusion of myristoyl-LPC at 13 +/- 3 pmol/min resulted in a small fall in systemic blood pressure, a 13% decrease in renal plasma flow without significantly altering glomerular filtration rate and produced a slightly greater excretion of sodium and water than vehicle controls. These results suggest that short term myristoyl-LPC administration can significantly alter renal function producing a weak natriuresis and diuresis which is not dependent on systemic blood pressure and renal hemodynamic changes.

Analysis of Variance↗
PubMed1991

Vasorelaxant effect of C16-PAF and C18-PAF on renal blood flow and systemic blood pressure in the anesthetized rat.

The renal vasoactive and systemic hypotensive effects of platelet activating factor (C16:0-PAF and C18:1-PAF) were examined in anesthetized male Wistar rats. Bolus injections of C16-PAF (0.5-25 ng/kg) and C18-PAF (2.5-200 ng/kg) into the arterial circulation of the kidney produced increases in renal blood flow (6-15%) before causing dose-dependent systemic hypotension (2-64 mmHg). The dose-response curves for renal blood flow and systemic blood pressure generated by intrarenal C18-PAF administration were approximately 7 fold to the right of the dose-response curves generated by C16-DPAF. Intrarenal injections of vehicle or the biologically inactive enantiomer C16-DPAF (25-200 ng/kg) did not affect renal blood flow or systemic blood pressure. These results suggest that C16:0-PAF is a more potent renal vasodilator and hypotensive lipid than C18:1-PAF.

Anesthesia↗
PubMed1991

Racial differences in HLA antigen frequency and hypertensive renal failure.

Black patients with hypertension are six times more likely to develop end-stage renal disease than are their white counterparts. To determine if genetic differences associated with the Human Leukocyte Antigen (HLA) system account for racial variation in hypertensive renal failure, we examined antigenic frequencies from a large renal transplant registry. Human Leukocyte Antigen phenotypes from cadaveric renal transplant recipients and donors in the South Eastern Organ Procurement Foundation database from 1982 to 1986 were analyzed. One thousand six hundred four renal transplant recipients with hypertensive renal failure as the cause of end stage renal disease (cases) were compared with 4506 race-matched cadaveric kidney donors (controls). Log-linear models were used to assess the relationship between hypertensive renal failure and prevalence of each HLA phenotype. Bonferroni adjustments of P values were used to correct for multiple comparisons. Comparison of HLA frequencies between blacks and whites with hypertensive renal failure demonstrated that blacks had an increased frequency of HLA-DR3 beyond that normally known to exist between black and white populations. Black cases compared to black controls had an 8.6% increase in HLA-DR3 frequency contrasted with a 1.6% decrease in the frequency of this antigen between white cases and white controls. This absolute 10.2% difference between the races was significant (P = .02) because the control black and white populations had nearly identical frequencies for this antigen. White cases compared to white controls had lower HLA-A1 and B8 frequencies (21.2% v 30.6%, P = .0005 and 13.7% v 22.3%, P = .001, respectively) and a greater HLA-B35 frequency (20.7% v 14.2%, P = .02).(ABSTRACT TRUNCATED AT 250 WORDS)

Black People↗
PubMed1991

Selective inhibition of vasoconstrictor responses by platelet-activating factor in rat kidney.

We examined the effect of platelet-activating factor (PAF) on renal vascular reactivity in the pentobarbital sodium-anesthetized male Wistar rat. Intrarenal infusion of C16-PAF at hypotensive (2.5 ng.min-1.kg-1) or nonhypotensive (0.5 ng.min-1.kg-1) doses caused renal vasodilation and dose dependently antagonized the renal vasoconstrictor responses of intrarenal boluses of angiotensin II (ANG II) greater than norepinephrine (NE) greater than vasopressin (AVP). PAF infusion at the high dose did not alter non-receptor-mediated renal vasoconstriction induced by intrarenal KCl injection. The inhibitory effect of PAF on agonist-induced renal vasoconstriction was accentuated by eicosanoid synthesis inhibition (indomethacin or dexamethasone), unaffected by dopamine-receptor blockade (haloperidol) but was totally abolished by PAF receptor antagonism (L-659,989). In contrast, intrarenal infusion of a calcium channel antagonist (nimodipine) or an intracellular calcium channel antagonist (TMB-8) equally inhibited the renal vasoconstrictor responses of ANG II, NE, and AVP. Thus PAF can cause renal vasodilation in the rat kidney and dose-dependently antagonizes the renal vasoconstrictor responses of ANG II greater than NE greater than AVP. The inhibitory effect of PAF on renal vasoconstrictor responses is mediated by PAF receptors and does not appear to be due to a nonspecific membrane effect, reduction in calcium mobilization, or the release of vasodilatory eicosanoids or dopamine.

Animals↗
PubMed1990

Regulation of plasma atrial natriuretic peptide by the central nervous system.

The anterior ventral region of the third ventricle (AV3V) is a major central site in the regulation of cardiovascular and renal function. To examine the role of the central nervous system in the regulation of atrial natriuretic peptide (ANP) secretion, the effect of lesions in this region on basal, volume-stimulated, and osmotic-stimulated plasma ANP was determined. Basal levels of plasma ANP were not different in sham- and AV3V-lesioned rats. Volume expansion with a continuous infusion of saline or with a bolus administration of saline increased plasma ANP in sham-lesioned rats. In AV3V-lesioned rats, continuous infusion of saline had no effect on plasma ANP, and a bolus administration of saline decreased plasma ANP. Osmotic stimulation with hypertonic saline increased plasma ANP in sham-lesioned rats but had no effect on plasma ANP in AV3V-lesioned rats. These results suggest that the central nervous system is involved in the regulation of ANP secretion and that altered ANP regulation may contribute to the cardiovascular and renal deficiencies in AV3V-lesioned rats.

Animals↗
PubMed1990

Platelet-activating factor is a renal vasodilator in the anesthetized rat.

In view of the potent vasoactive properties of platelet-activating factor (PAF), we investigated the renal hemodynamic effects of this lipid. C16-PAF (0.5-10 ng/kg) given as a bolus into the renal arterial circulation of pentobarbital sodium-anesthetized male Wistar rats produced a dose-dependent increase in renal blood flow (6-15%), before causing systemic hypotension. The PAF-induced renal vasodilation and systemic hypotension was independent of renal innervation, unaltered by eicosanoid synthesis inhibition with indomethacin or dexamethasone, unchanged by the nonselective dopamine-receptor antagonist haloperidol, but was abolished by the PAF-receptor antagonist, L-659,989. Non-hypotensive intrarenal PAF infusion at 0.5 ng.min-1.kg-1 caused an increase in renal blood flow. Thus PAF can cause renal vasodilation in the rat kidney that is PAF-receptor mediated and does not involve the sympathetic nervous system or the release of vasodilatory arachidonic acid metabolites or dopamine.

Anesthesia↗
PubMed1989

Analgesic use and chronic renal disease.

To examine the use of analgesics as a cause of chronic renal disease, we performed a multicenter case-control study of 554 adults with newly diagnosed kidney disease (serum creatinine, greater than or equal to 130 mumol per liter [1.5 mg per deciliter]) and 516 matched control subjects selected randomly from the same area of North Carolina. Histories of use of analgesics (phenacetin, acetaminophen, and aspirin) were obtained by telephone interview with the patients or their proxies. Daily users of analgesics had significantly more renal disease than infrequent users (odds ratio, 2.79; 95 percent confidence interval, 1.85 to 4.21). The risk of renal disease was highest in daily users of phenacetin (odds ratio, 5.11; confidence interval, 1.76 to 14.9, after adjustment for the effects of other analgesics). The risk of renal disease was also increased in daily users of acetaminophen; after adjustment for the use of aspirin and phenacetin, the odds ratio was 3.21 (confidence interval, 1.05 to 9.80). There was no increased risk in daily aspirin users (adjusted odds ratio, 1.32; confidence interval, 0.69 to 2.51). The risks with daily use of either phenacetin or acetaminophen changed little after adjustment for diabetes, hypertension, and the indication for analgesic use. We conclude that the long-term, regular use of phenacetin may increase the risk of chronic renal disease. The long-term, daily use of acetaminophen, the major metabolite of phenacetin, is associated independently with an increased risk of chronic renal disease. We could find no increased risk in daily users of aspirin.

Acetaminophen↗
PubMed1989

Nephrolithiasis in renal tubular acidosis.

Renal tubular acidosis is a term applied to several conditions in which metabolic acidosis is caused by specific defects in renal tubular hydrogen ion secretion. Three types of renal tubular acidosis generally are recognized based on the nature of the tubular defect. Nephrolithiasis occurs only in type I renal tubular acidosis, a condition marked by an abnormality in the generation and maintenance of a hydrogen ion gradient by the distal tubule. A forme fruste of type I renal tubular acidosis has been described in which the characteristic defect in distal hydrogen ion secretion occurs in the absence of metabolic acidosis (incomplete renal tubular acidosis). Type I renal tubular acidosis is a heterogeneous disorder that may be hereditary, idiopathic or secondary to a variety of conditions. Secondary type I renal tubular acidosis in sporadic cases is associated most commonly with autoimmune diseases, such as Sjögren's syndrome and systemic lupus erythematosus, and it occurs more frequently in women than men. Nephrolithiasis, which may occur in any of the subsets of type I renal tubular acidosis, accounts for most of the morbidity in adults and adolescents. Major risk factors for nephrolithiasis include alkaline urine, hypercalciuria and hypocitraturia. In addition, we found hyperuricosuria in 21 per cent of the patients with type I renal tubular acidosis with nephrolithiasis. The most frequently occurring risk factor, hypocitraturia, is due to decreased filtered load and/or to increased tubular reabsorption of filtered citrate. While increased tubular reabsorption may be due to systemic acidosis, hypocitraturia occurs in incomplete renal tubular acidosis. Furthermore, alkali therapy (either bicarbonate or citrate salts) increases citrate excretion in complete and incomplete type I renal tubular acidosis. These data suggest that hypocitraturia in type I renal tubular acidosis may be due to a defect in proximal tubule function. Hypercalciuria appears to have 2 causes. It may be due to metabolic acidosis, usually in children with a hereditary defect in urine acidification. In other cases familial idiopathic hypercalciuria causes nephrocalcinosis and nephrolithiasis resulting in distal tubular damage and type I renal tubular acidosis. In these latter cases hypercalciuria is present in complete and incomplete type I renal tubular acidosis. Potassium citrate appears to reduce calcium excretion in both types of hypercalciuric type I renal tubular acidosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Acidosis, Renal Tubular↗
PubMed1989

Erythrocyte sodium concentration and 86Rb uptake in weanling Dahl rats.

Alterations in Na, K ATPase pump activity as well as erythrocyte (RBC) intracellular sodium concentration (Nai) have been demonstrated in humans and rats with established hypertension. The contribution of hypertension itself to these changes is unclear. Accordingly, we investigated RBC ion transport and plasma ouabain-like factor (OLF) in four- to five-week old normotensive Dahl salt-sensitive (DS) and salt-resistant (DR) rats on low salt diet. Although both strains were normotensive, systolic blood pressure (SBP) of DS (123 +/- 2 mm Hg) was higher than that of DR (116 +/- 1 mm Hg). No interstrain difference was evident in RBC pump activity measured as ouabain-sensitive 86rubidium (86Rb) uptake (DS = 0.277 +/- .030 and DR = 0.271 +/- .029 mumol/10(9)RBC/h) even though RBC Nai was greater in DS than DR (14.9 +/- 2.0 v 10.7 +/- 1.0 mEq/L; P less than 0.05). Plasma OLF was higher in DS than DR (28.9 +/- 4.7 v 16.5 +/- 2.3 pmol/mL; P less than 0.05), but did not correlate with RBC pump activity in either strain. RBC Nai was directly correlated with pump activity in DS (r = 0.84, P less than 0.01) and demonstrated a trend to correlate in DR (r = 0.71, P = 0.07). RBC Nai was also directly correlated with SBP in DR (r = 0.73, P less than 0.05) and DS (r = 0.70, P = 0.05). We conclude that RBC Nai is genetically determined in Dahl rats and is elevated in normotensive DS who are at risk for hypertension development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Plasma volume in resistant hypertension: guide to pathophysiology and therapy.

It might be expected that the tremendous increase in available antihypertensives would eliminate resistant hypertension by allowing many alternatives to its treatment. In spite of this, resistant hypertension remains a common problem due, the authors feel, to a poor understanding of the pathophysiology of this condition, particularly an understanding of whether plasma volume expansion mediates resistance to antihypertensive therapy. The authors evaluated the status of plasma volume as a major determinant of response to therapy in nine patients with resistant hypertension. Measuring plasma volume using I125 radiolabeled albumin, they found eight patients with elevated plasma volumes and one patient with a contracted plasma volume at the time of presentation with resistant hypertension. In all eight patients with plasma volume expansion, aggressive diuretic therapy allowed goal blood pressure to be achieved. The patient with plasma volume contraction achieved goal blood pressure with vasodilator therapy. Plasma volume expansion is common in resistant hypertension and it mediates resistance to therapy. Measurement of plasma volume gives the clinician important insight into the pathophysiology of resistant hypertension and increases the likelihood of successful management of the resistant hypertensive patient.

Adult↗
PubMed1989

Differential effect of dietary salt on renal growth in Dahl salt-sensitive and salt-resistant rats.

A high salt diet has been shown to increase renal mass of intact rats, although the mechanism by which this occurs has not been investigated. We used Dahl rats that are sensitive (DS) or resistant (DR) to the hypertensinogenic effect of salt to examine changes in renal size and composition caused by a high salt diet. Renal index, deoxyribonucleic acid (DNA), protein, water content, protein/DNA ratio, and cell number and size were measured in age-matched DR and DS on a high salt diet for 7, 14, or 28 days. The results were compared with those obtained from respective rats on a low salt diet. High salt diet elevated renal index and protein in DR and DS rats at each time point. After 7 days of a high salt diet, DNA increased in DS only. Protein/DNA ratio was progressively decreased by a high salt diet in DS and remained unchanged in DR rats. Cell number was increased 35% in DS versus only 13% in DR rats at 4 weeks. Cell size decreased 24% in DS and only 11% in DR rats. These results indicate that renal growth due to hyperplasia accompanies ingestion of a high salt diet in both DR and DS rats, but the rate of growth and the mechanism through which it occurs differ between strains. This difference may be important in delineating salt sensitivity and future development of hypertension.

Animals↗
PubMed1988

Tissue distribution of an endogenous ligand to the Na, K ATPase molecule.

A variety of evidence indicates the presence of a circulating ligand to the Na, K ATPase molecule that is involved in the regulation of extracellular sodium metabolism. To examine the potential role of endogenous ligands to the Na, K ATPase molecule in the regulation of intracellular sodium metabolism, the tissue distribution of digitalis-like activity was quantitated in several brain regions and peripheral organs. The digitalis-like activity of desalted and delipidated extracts of tissue was widely distributed and produced a displacement of tritiated ouabain that was parallel to the displacement produced by cold ouabain. These results suggest that tissue contains an endogenous ligand to the Na, K ATPase molecule and that this ligand may regulate intracellular sodium metabolism in an autocoid-like manner.

Animals↗
PubMed1988

Characterization of a competitive and reversible ligand to E2 conformation of Na, K ATPase molecule.

The binding of cardiac glycosides to the E2 conformation of Na, K ATPase suggests that this conformation may represent a potential regulatory site for an endogenous ligand. To examine this hypothesis, delipidated and desalted, ethanolic extracts were prepared from plasma. Plasma extracts produced displacement of 3H-ouabain from Type I and II high affinity binding sites that was parallel to the displacement by cold ouabain. Plasma extracts shifted the binding curve of 3H-ouabain to the right indicating a competitive and reversible displacement. Extracts also produced a dose-dependent inhibition of Na, K ATPase and K-stimulated, p-nitrophenyl phosphatase activity. These results indicate that this ligand may function as an endogenous ligand to the E2 conformation of the Na, K ATPase molecule and be involved in its regulation.

Animals↗
PubMed1988

Circulating digitalis-like factors.

The ability of extracts of mammalian plasma and tissue to mimic the biologic activities of the digitalis glycosides has suggested the existence of endogenous regulators for Na, K ATPase. Purification of plasma extracts has identified several classes of circulating lipids with digitalis-like activity including free fatty acids, lysophospholipids, and arachidonic acid metabolites of the lipoxygenase pathway. Circulating steroids with digitalis-like activity include dehydroepiandrosterone sulfate and hydrocortisone. Evidence for other, more unique compounds has also been published although their structure has not yet been determined. Analysis of tissue suggests that hypothalamus contains a unique, low molecular digitalis-like factor (DLF) which also circulates in plasma. Some studies suggest that the hypothalamic factor is also present in other parts of the brain and in the adrenal. Some of these endogenous DLF may function as modulators of cardiovascular function by regulating renal sodium excretion and peripheral vascular resistance in both physiological and pathophysiological situations.

Animals↗