Hypokalemia induces renal injury and alterations in vasoactive mediators that favor salt sensitivity

We investigated the hypothesis that hypokalemia might induce renal injury via a mechanism that involves subtle renal injury and alterations in local vasoactive mediators that would favor sodium retention. To test this hypothesis, we conducted studies in rats with diet-induced K+ deficiency. We also determined whether rats with hypokalemic nephropathy show salt sensitivity. Twelve weeks of hypokalemia resulted in a decrease in creatinine clearance, tubulointerstitial injury with macrophage infiltration, interstitial collagen type III deposition, and an increase in osteopontin expression (a tubular marker of injury). The renal injury was greatest in the outer medulla with radiation into the cortex, suggestive of an ischemic etiology. Consistent with this hypothesis, we found an increased uptake of a hypoxia marker, pimonidazole, in the cortex. The intrarenal injury was associated with increased cortical angiontensin-converting enzyme (ACE) expression and continued cortical angiotensin II generation despite systemic suppression of the renin-angiotensin system, an increase in renal endothelin-1, a decrease in renal kallikrein, and a decrease in urinary nitrite/nitrates and prostaglandin E(2) excretion. At 12 wk, hypokalemic rats were placed on a normal-K+ diet with either high (4%)- or low (0.01%)-NaCl content. Despite correction of hypokalemia and normalization of renal function, previously hypokalemic rats showed an elevated blood pressure in response to a high-salt diet compared with normokalemic controls. Hypokalemia is associated with alterations in vasoactive mediators that favor intrarenal vasoconstriction and an ischemic pattern of renal injury. These alterations may predispose the animals to salt-sensitive hypertension that manifests despite normalization of the serum K+.

Pathogenesis of Shiga toxin-induced hemolytic uremic syndrome

The term hemolytic uremic syndrome (HUS) was first introduced to describe a heterogeneous group of diseases characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. Substantial progress has been made in our understanding of the etiology and pathogenesis of HUS. This article reviews some of the classic and new concepts related to the pathogenesis of Shiga toxin (Stx)-HUS and discusses their clinical relevance for the diagnosis and treatment of this syndrome. Infection with Stx-producing bacteria can induce HUS after a prodromal illness with or without diarrhea. Stx-induced renal endothelial injury is the primary pathogenic event. However, Stx also damages mesangial cells, as well as glomerular and renal tubular epithelial cells. Young children are at greatest risk for Stx-HUS because they express high levels of Stx receptors in renal glomeruli. Older children and adults express lower levels of glomerular Stx receptors and may develop Stx-HUS whenever the combined effects of lipopolysaccharide and cytokines upregulate the expression of Stx receptors and sensitize glomerular endothelial cells to Stx-induced injury, activate the coagulation-fibrinolytic system, and induce endothelial injury. Chemokine receptors and cytokines released by inflammatory cells (i.e., monocyte chemoattractant protein-1, interleukin-6, interleukin-8,) or injured endothelial cells (i.e., basic fibrobast growth factor) may play roles in this process. Measurement of the activity of a von Willebrand factor protease in plasma may help distinguish patients with thrombotic thrombocytopenic purpura from those with Stx-HUS.

Chronic potassium depletion induces renal injury, salt sensitivity, and hypertension in young rats

BACKGROUND

Chronic hypokalemia has been associated with renal hypertrophy, interstitial disease, and hypertension in both adult animals and humans. However, the effects of potassium (K(+)) depletion on the rapidly growing infant have not been well studied. The purpose of this study was to determine the effects of severe chronic dietary K(+) depletion on blood pressure (BP) and renal structural changes in young rats.

METHODS

Sprague-Dawley rats (50 +/- 5 g) were fed either a control or a potassium-deficient diet (<0.05% K(+)) for 14 to 21 days. At the end of this period, the blood pressure (BP) was measured in all rats, and six rats in each group were sacrificed to determine changes in renal histology and renin-angiotensin system (RAS) activity. The remaining rats in each group were then switched to a high-salt (6% NaCl)--normal-K(+) (0.5%) diet or were continued on their respective control or K(+)-deficient diet for an additional six days. Blood pressure measurements were done every three days until the end of the study.

RESULTS

K(+)-depleted animals had significant growth retardation and increased RAS activity, manifested by high plasma renin activity, recruitment of renin-producing cells along the afferent arterioles, and down-regulation of angiotensin II receptors in renal glomeruli and ascending vasa rectae. K(+)-depleted kidneys also showed tubulointerstitial injury with tubular cell proliferation, osteopontin expression, macrophage infiltration, and early fibrosis. At week 2, K(+)-depleted rats had higher systolic BP than control rats. Switching to a high-salt (6% NaCl)--normal-K(+) diet resulted in further elevation of systolic BP in K(+)-depleted rats, which persisted even after the serum K(+) was normalized.

CONCLUSION

Dietary potassium deficiency per se increases the BP in young rats and induces salt sensitivity that may involve at least two different pathogenic pathways: increased RAS activity and induction of tubulointerstitial injury.

Up-regulation of a fibroblast growth factor binding protein in children with renal diseases

BACKGROUND

Basic fibroblast growth factor (bFGF) is an angiogenic growth factor that is involved in renal growth and the pathogenesis of renal diseases. We have detected high levels of bFGF accumulated in the kidney of HIV-transgenic mice and in children with HIV-associated renal diseases and the hemolytic uremic syndrome (HUS). However, the mechanism modulating the activity of bFGF under these circumstances is poorly understood. We carried out experiments to determine whether a secreted binding protein (FGF-BP) that modulates the activity of bFGF during the process of tumor growth was expressed in pediatric kidneys and to define whether the expression of FGF-BP was altered in pediatric renal diseases associated with high levels of bFGF.

METHODS

Immunohistochemistry and in situ hybridization studies were done in 41 renal sections from children with HIV nephropathies, HUS, other pediatric renal diseases, controls, and fetal kidneys. Western blots and reverse transcriptase-polymerase chain reaction studies were done in selected urine samples and cultured renal cells. Recombinant FGF-BP was produced to study the mitogenic activity of FGF-BP in cultured human renal proximal tubular epithelial cells (RPTEcs).

RESULTS

The expression of FGF-BP was up-regulated predominately in renal tubular epithelial cells in children with renal tubular injury, HIV-associated nephropathy (HIVAN), and HUS, and FGF-BP was secreted in the urine of these patients. FGF-BP was also abundantly expressed in developing fetal renal tubules. Recombinant FGF-BP enhanced the mitogenic effects of bFGF in cultured human RPTEcs.

CONCLUSIONS

The localization of FGF-BP in renal tubular epithelial cells could provide a mechanism by which the activity of bFGF is modulated in developing and regenerating renal tubules of children.

Efficient gene transfer to rat renal glomeruli with recombinant adenoviral vectors

Recombinant adenoviruses are attractive vectors for renal gene transfer since they can efficiently transduce nondividing cells. However, despite the fact that renal glomeruli are easily accessible via the renal circulation, attempts to deliver foreign genes specifically into renal glomeruli, using adenoviral vectors, have had limited success in rodents. A simple intraarterial injection of adenoviral vectors into the renal circulation or incubation of the virus with the kidney for an extended period of time was found to be insufficient for this purpose. In this study, we have established an efficient gene transfer protocol to express foreign genes in rat renal glomerular cells, using adenoviral vectors. We demonstrated, for the first time, that rat glomerular endothelial cells could be efficiently transduced by slowly infusing a recombinant adenovirus (Ad.CBlacZ) into the right renal artery for a period of 15 min. High levels of lacZ expression were achieved in renal glomeruli without causing significant damage to renal glomeruli or other kidney structures. The virus-mediated expression lasted for at least 21 days. These data demonstrate the feasibility of using recombinant adenoviral vectors as a tool with which to study the effect of foreign gene expression on the structure and function of rat renal glomeruli in vivo.

Expression of renal and vascular angiotensin II receptor subtypes in children

Angiotensin II (Ang II) AT1 receptors modulate most of the known physiological functions of Ang II in the kidney and cardiovascular structures. In contrast, the physiological role of AT2 receptors, which are abundantly expressed in fetal tissues, is not clearly defined. The changes that occur in the expression and distribution of AT2 receptors in the kidney and arteries during the first 2 years of life have not been studied. We have localized and characterized the expression of Ang II receptor subtypes, AT1 and AT2, in the kidney, interlobular arteries, thoracic aorta, and middle cerebral artery, in children during their first 2 years of life, using quantitative autoradiography. Renal glomeruli and middle cerebral arteries expressed exclusively AT1 receptors. In contrast, more than 80% of the Ang II receptors expressed in thoracic aorta and interlobular arteries belonged to the AT2 subtype. These findings demonstrate that the expression of Ang II receptor subtypes in different vascular structures in young children varies according to the tissue.

Isoproterenol inhibits fibroblast growth factor-2-induced growth of renal epithelial cells

The signal transduction pathways modulating bFGF effects in renal tubular epithelial cells (RTEc) are not completely understood. Since the cAMP and the mitogen-activated protein kinase (MAPK) pathways can modulate the growth of RTEc, we studied whether two cAMP elevating agents, isoproterenol and 8-bromo-cAMP, would modulate basic fibroblast growth factor (bFGF) induction of MAPK activity (ERK-2) and cell proliferation in human renal proximal tubular epithelial cells (RPTEc) and Madin-Darby canine kidney cells (MDCK clone EI1). Isoproterenol, but not bFGF, stimulated cAMP production in RPTEc and MDCKEI1 cells. bFGF, isoproterenol, and 8-bromo-cAMP alone increased ERK-2 activity in both cell types. However, isoproterenol and 8-bromo-cAMP partially inhibited the bFGF induction of ERK-2 activity, but only isoproterenol inhibited the proliferation of both cell types. PD098059 (25 microM), an inhibitor of MAPK kinase (MEK 1/2), blocked the bFGF mitogenic effects, but did not affect the 8-bromo-cAMP-induced mitogenic effects in MDCKEI1 cells. These findings suggest that activation of ERK-2 is required but not sufficient for mitogenesis in RTEc. We conclude that isoproterenol inhibits the growth-promoting effects of bFGF in RTEc via MEK-dependent and -independent pathways.

Angiotensin II and basic fibroblast growth factor mitogenic pathways in human fetal mesangial cells

Angiotensin II (Ang II) and basic fibroblast growth factor (bFGF/FGF-2) play relevant roles in renal development. Since the signaling pathways modulating the mitogenic effects of Ang II and bFGF in human fetal mesangial cells (HFMc) are not clearly defined, we carried out experiments to determine whether they would exert their mitogenic effects by modulating the activity of the mitogen-activated protein kinases (MAPK) [extracellular signal-regulated kinase-2 (ERK-2)] and cAMP signaling pathways. In confluent HFMc, bFGF (20 ng/mL) induced a significant 4-fold increase in ERK-2 activity and [3H]-thymidine incorporation (6-fold). In contrast, under similar tissue culture conditions, Ang II (10(-6) M) induced a more modest increase in ERK-2 activity (2-fold) and [3H]-thymidine incorporation (35 +/- 4%). The mitogen-activated protein kinase kinase-1 (MEK-1) inhibitor PD098059 (25 microM) almost completely abolished the bFGF-induced proliferation in HFMc but did not significantly affect Ang II proliferative effects. In the presence of the cAMP elevating agent isoproterenol, Ang II and bFGF induced opposite changes in cAMP accumulation and cell growth. Isoproterenol inhibited the basal and bFGF-induced proliferation of HFMc through a MEK-1/2-independent pathway that included the accumulation of cAMP. In contrast, isoproterenol increased Ang II mitogenic effects in correlation with a reduction in cAMP accumulation. We conclude that Ang II and bFGF modulate the proliferation of HFMc through the stimulation of different MEK-1/2-dependent and independent signaling pathways. Activation of MEK-1/2 is required but not sufficient for mitogenesis in HFMc. The accumulation of cAMP in HFMc counteracts the mitogenic effects of bFGF by a MEK-1/2-independent pathway.

Liver bypass significantly increases the transduction efficiency of recombinant adenoviral vectors in the lung, intestine, and kidney

Recombinant adenoviruses have great potential as gene delivery systems because of their ability to infect a wide range of target cells. However, systemic delivery of viral vectors to tissues other than liver and spleen has been inefficient because of the rapid clearance of the circulating virus by the liver. In the present study we tested the hypothesis that a systemic administration of E1-deleted recombinant adenovirus vectors that bypasses the hepatic circulation will lead to enhanced expression of these vectors in extrahepatic tissues. The portal vein and hepatic artery in B6/129 F1 mice were clamped and an E1-deleted recombinant adenovirus carrying the beta-galactosidase gene (Ad.CBlacZ) was then administered through the retroorbital venous plexus. The clamp was released 30 min after viral injection with no major chronic ischemic consequences noted. High levels of LacZ expression were detected predominantly in the vessels and capillaries of the lung, intestinal wall, and renal glomeruli 7 days after viral infusion. The transgene expression persisted for at least 21 days. Intense LacZ staining was also observed in the liver, suggesting that liver infection occurred after the portal clamp was released. A retroorbital infusion of anti-adenovirus neutralizing antibodies 5 min before the release of the portal clamp significantly reduced postclamp viral infection to the liver, while LacZ expression in lung and intestine persisted after the antibody treatment. Taken together, these results suggest that liver bypass can significantly improve the transduction efficiency in the other target organs. This method could be used to develop animal models of human diseases that predominantly affect the vessels of the lung, intestine, and kidney.

Basic fibroblast growth factor in HIV-associated hemolytic uremic syndrome

Endothelial injury is the primary pathogenic event leading to the renal thrombotic microangiopathic lesions typical of the hemolytic uremic syndrome (HUS). Basic fibroblast growth factor (bFGF) is an angiogenic growth factor released by injured endothelial cells. In a previous study we have found a significant accumulation of bFGF in human immunodeficiency virus (HIV)-transgenic mice with renal disease. Here we investigated whether bFGF was accumulated in the circulation and kidneys of two children with HIV-associated HUS (HIV-HUS), and studied the mechanisms involved in this process. The plasma levels of bFGF in children with HIV-HUS (124+/-20 pg/ml) were increased compared with five children with HIV nephropathy (49+/-6 pg/ml) and twenty HIV-infected children without renal disease (26+/-4 pg/ml, P<0.001). Immunohistochemistry and receptor binding studies showed that bFGF was accumulated bound to heparan sulfate proteoglycans in renal glomeruli and interstitium surrounding renal tubules in HIV-HUS kidneys. Basic FGF stimulated the proliferation of mesangial and urinary renal tubular epithelial cells isolated from both patients. These findings support the hypothesis that bFGF and its low-affinity binding sites may play a relevant role in modulating the process of glomerular and renal tubular regeneration during the acute stages of HIV-HUS. A follow-up study in a larger sample population is required to confirm these results.

Up-regulation of Duffy antigen receptor expression in children with renal disease

BACKGROUND

The Duffy antigen chemokine receptor (DARC) is a promiscuous chemokine receptor that binds chemokines from the C-X-C and C-C families. DARC was initially described on red blood cells, but subsequent studies have demonstrated DARC protein expression on renal endothelial and epithelial cells, even in Duffy-negative individuals whose red cells lack DARC. Because approximately 68% of African Americans lack the Duffy/DARC on their red cells, we carried out experiments to identify the specific renal cells expressing DARC protein and mRNA in African American children and to define whether DARC expression was altered in renal inflammatory processes.

METHODS

Immunohistochemistry and in situ hybridization studies were done in 28 renal sections from children with each of the following diagnoses: HIV nephropathy (HIVAN), HIV-associated hemolytic uremic syndrome (HIV-HUS), HIV infection without renal disease, HIV-negative children without renal disease, and Argentinean children with classic HUS.

RESULTS

The predominant localization of DARC mRNA and protein was found in endothelial cells underlying postcapillary renal venules in all patients studied. However, DARC mRNA and protein were significantly up-regulated in peritubular and glomerular capillaries, collecting duct epithelial cells, and interstitial inflammatory cells in children with HIVAN, HIV-HUS, and classic HUS.

CONCLUSION

These findings support the notion that the renal DARC is linked to the inflammatory cascade and that African American children may be at risk of accumulating chemokines in renal tissues.

Recruitment of renal tubular epithelial cells expressing verotoxin-1 (Stx1) receptors in HIV-1 transgenic mice with renal disease

BACKGROUND

Human immunodeficiency virus (HIV)-infected children are at risk of developing several renal parenchymal diseases, including hemolytic uremic syndrome (HUS). HUS is most frequently caused by infection with enteric Escherichia coli producing Shiga-like toxins (Stxs). In vitro studies have shown that cytokines known to be present at high systemic levels in HIV-1-infected children up-regulate the expression of the Stx glycolipid receptor (Gb3) in cultured endothelial cells. Thus, we studied whether HIV-1 or the HIV-associated "cytokine milieu" could modulate the expression of renal Stxs receptors in vivo.

METHODS

We used HIV-1 transgenic mice (HIV-Tg) expressing a deletion mutant of HIV-1 (pNL4-3). These mice develop renal disease similar to that of HIV-1-infected children. The expression of Gb3 was studied in renal sections from control and HIV-Tg mice by histochemistry, thin layer chromatography overlay studies, and high-pressure liquid chromatography.

RESULTS

By histochemistry, we found a significant recruitment of renal tubular epithelial cells expressing Gb3 in HIV-Tg mice with nephropathy, whereas kidneys from control mice showed limited staining in renal tubules. Gb3 was not found in glomeruli of either control or HIV-Tg mice. Thin layer chromatography overlay studies with Stxs and high-pressure liquid chromatography studies confirmed the marked elevation of Gb3 in HIV-Tg kidneys with renal disease.

CONCLUSIONS

These results suggest that the presence of HIV-associated nephropathy is associated with the recruitment of renal tubular epithelial cells expressing Stx1 receptors. The up-regulation of Stx1 receptors in HIV-diseased kidneys may increase the sensitivity of these cells to the cytotoxic effects of Stxs.

Human immunodeficiency virus (HIV)-associated nephropathy in children from the Washington, D.C. area: 12 years' experience

Human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) is a clinicopathologic entity that includes proteinuria, azotemia, focal segmental glomerulosclerosis or mesangial hyperplasia, and tubulointerstitial disease. The incidence of HIVAN is increased in black patients and variable depending on the age and geographic area. The objective of this study was to describe relevant clinical and pathological findings in 30 children with HIVAN followed at the Children's National Medical Center in Washington, D.C. Our experience of the last 12 years showed a spectrum of HIVAN that seems to be coincident with the degree of acquired immunodeficiency syndrome (AIDS) symptomatology. By renal sonograms and frequent urinalysis, we identified children undergoing the early stages of HIVAN with enlarged echogenic kidneys, proteinuria, and "urine microcysts". HIVAN did not necessarily progress rapidly to end-stage renal disease. Nephrotic syndrome or chronic renal insufficiency were late manifestations of HIVAN. Children with HIVAN were likely to develop transient electrolyte disorders, heavy proteinuria, and acute renal failure due to systemic infectious episodes or nephrotoxic drugs. HIVAN was associated with other HIV-induced illnesses and high mortality rates. Early detection and careful clinical follow-up of children with HIVAN may reduce the incidence of renal-cardiovascular complications and improve their quality of life.

Infection of human primary renal epithelial cells with HIV-1 from children with HIV-associated nephropathy

Children affected with human immunodefficiency virus (HIV)-associated nephropathy (HIVAN) usually develop significant renal glomerular and tubular epithelial cell injury. The pathogenesis of these changes is not clearly understood. Human renal tubular epithelial cells (RTEc) do not express CD4 surface receptors, and it is not clear whether these cells can be infected by HIV-1. Certain strains of HIV-1, however, have been shown capable of infecting CD4-negative epithelial cell lines. We hypothesized that the inability of laboratory strains of HIV-1 to infect renal epithelial cells may be due to a limited tropism, as opposed to wild-type viruses derived from children with HIVAN, and that viruses derived from these children are capable of infecting RTEc from the same patient. Here, we have demonstrated that HIV-1 isolates from children with HIVAN can productively infect RTEc through a CD4 independent pathway, and that infected mononuclear cells can transfer the virus to human RTEc. Human RTEc sustained low levels of viral replication and HIV-1 inhibited the growth and survival of cultured human RTEc. Thus, HIV-1 may directly induce degenerative changes in RTEc of children with HIVAN. Infected macrophages may play a relevant role in this process by transferring viruses to RTEc.

Selective chronic sodium or chloride depletion specifically modulates subfornical organ atrial natriuretic peptide receptor number in young rats

1. We studied the effects of selective chronic sodium depletion of chloride depletion on atrial natriuretic peptide receptor number in the subfornical organ and paraventricular nucleus of young rats. 2. Sodium or chloride depletion decreased plasma levels of atrial natriuretic peptide, increased plasma renin activity, and induced extracellular fluid volume contraction. Chloride depletion induced more significant changes in extracellular fluid volume contraction than sodium depletion. 3. In the subfornical organ, atrial natriuretic peptide receptor number significantly decreased (30%) after sodium depletion, while chloride depletion induced a smaller, not statistically significant decrease. Conversely, atrial natriuretic peptide receptors located in the paraventricular nucleus of young rats were not significantly affected by sodium or chloride depletion. 4. Water deprivation reversed the decrease in atrial natriuretic peptide receptors produced by sodium depletion. Water-deprived sodium-depleted rats actually had higher numbers of atrial natriuretic peptide receptors in the subfornical organ than control rats. These changes were associated with severe extracellular fluid volume contraction and up regulation of brain vasopressin mRNA steady-state levels. Thus, the direction of change in the number of subfornical organ atrial natriuretic peptide receptors was dependent on the degree of extracellular fluid volume contraction. 5. Our results suggest that atrial natriuretic peptide receptors located in the subfornical organ, and not in the paraventricular nucleus, are selectively regulated by sodium depletion and extracellular fluid volume contraction.

A typical hemolytic uremic syndrome in human immunodeficiency virus-1-infected children

We describe the clinical and pathological findings of the hemolytic uremic syndrome (HUS) in two children with human immunodeficiency virus (HIV) infection. Both patients presented with microangiopathic hemolytic anemia, thrombocytopenia, and subsequently developed renal failure. The diagnosis of HUS was confirmed by renal histopathology in both patients. None of these children presented with bloody diarrhea, evidence of circulating antibody response to Escherichia coli O157 lipopolysaccharide, or other known risk factors for HUS, except for the presence of HIV infection. Each patient was treated with intravenous plasma infusion and renal replacement therapy. Their clinical course was characterized by non-oliguria and lack of significant hypertension throughout the acute phase of the disease. Despite these favorable clinical parameters, both patients developed end-stage renal failure. The etiology of this atypical HUS characterized by poor renal survival remains unknown and the role of HIV infection in its pathogenesis, although possible, is unclear.

Sodium or chloride deficiency lowers muscle intracellular pH in growing rats

Sodium deficiency and chloride deficiency are associated with a contracted extracellular (ECF) volume and impaired growth in young children and growing rats. In cell culture, lowering sodium in the medium reduces growth factor-stimulated Na+/H+ exchange activity, intracellular pH (pHi), and DNA synthesis. We studied the effect of chronic sodium deficiency and chloride deficiency upon growth, extracellular acid base status, and muscle pHi in young rats. We fed growing rats for 21 days either a control diet, or one deficient in sodium (0.005%), chloride (0.005%), or calories. Muscle pHi was measured using 31phosphorus nuclear magnetic resonance spectroscopy. Rats fed either the sodium-deficient or chloride-deficient diet developed ECF volume contraction and hyponatremia; growth in length and weight was impaired. Muscle pHi was decreased (pHi = 7.074 +/- 0.006, 7.078 +/- 0.006 vs. control 7.100 +/- 0.002; P < 0.02). In calorie-restricted rats, growth was impaired but pHi was not affected (pHi 7.103 +/- 0.008). Metabolic alkalosis developed in the chloride-deficient group; acid base status was not affected in the sodium-deficient group. Despite differences in ECF acid base status, both groups had a low muscle pHi. We speculate that the low muscle pHi was a result of the ECF volume contraction and hyponatremia; low muscle pHi may contribute to retarded cell growth.

Maternal-fetal interactions affect growth of human immunodeficiency virus type 1 transgenic mice

Infants vertically infected with human immunodeficiency virus type 1 (HIV-1) often manifest profoundly deficient growth with failure to thrive. The pathologic mechanisms that produce growth failure associated with pediatric HIV infection are not clear. Transgenic mice homozygous for a gag/pol deletion mutant of the infectious provirus pNL4-3 have been found to manifest a similar growth failure pattern. To explore the influence of HIV-1 on fetal growth and maternal-fetal interactions, we examined intrauterine growth of transgenic and nontransgenic mice and evaluated the consequence of embryo transfer into normal and heterozygous transgenic mothers. Mice homozygous for the HIV transgene had normal intrauterine and birth weights but uniformly displayed severe growth retardation postnatally. Transgene expression was prominent in transgenic fetuses and their placentas and in uteri of transgenic mothers, as determined by Northern analysis. Although embryo transfer did not affect intrauterine growth, the pregnancy rate in transgenic mothers was markedly lower than in nontransgenic controls. In both fetal and neonatal tissues, transgene expression was significantly greater in homozygous animals when compared with heterozygotes, but the difference was magnified postnatally. These results suggest that HIV gene expression affected both mother and neonate. In the mother, expression of the HIV-1 transgene reduced postfertilization pregnancy rate. Once the animal was pregnant, however, the effects of transgene expression on the homozygous fetus were overcome in utero, possibly by the contribution of maternal factors or by inhibition of HIV-1 gene expression by a fetal or maternal factor(s). In the neonate, HIV-1 transgene expression increased dramatically in homozygotes and was associated with profound growth failure.(ABSTRACT TRUNCATED AT 250 WORDS)

bFGF and its low affinity receptors in the pathogenesis of HIV-associated nephropathy in transgenic mice

HIV-associated nephropathy is characterized by extensive tubulointerstitial disease with epithelial cell injury, microcystic proliferation, and tubular regeneration with glomerulosclerosis. To explore the role of bFGF as a mediator of HIV-induced interstitial disease, we utilized an HIV transgenic mouse model that manifests clinical and histological features observed in patients. In transgenic mice, simultaneous renal epithelial cell proliferation and injury were detected in vivo. In areas of microcystic proliferation, immunoreactive bFGF colocalized with extracellular matrix. Kidneys from transgenic mice had increased bFGF low affinity binding sites, particularly in the renal interstitium. In vitro, transgenic renal tubular epithelial cells proliferated more rapidly and generated tubular structures spontaneously, in marked contrast to nontransgenic renal cells where these pathologic features could be mimicked by exogenous bFGF. These studies suggest that renal bFGF and its receptors play an important role in the pathogenesis of HIV-associated nephropathy.

Angiotensin II stimulates human fetal mesangial cell proliferation and fibronectin biosynthesis by binding to AT1 receptors

The renin-angiotensin system is activated during vascular development and injury. Furthermore, angiotensin II (Ang II) is a comitogen for fetal mesangial cells in vitro and it may be important in vascular smooth cell growth in disease states. Since fibronectin is an important extracellular matrix protein for vascular development and it too is overexpressed in the mesangium of diseased glomeruli, we explored the interrelationship of fibronectin and Ang II in fetal mesangial cell growth. In human fetal kidney, Ang II type 2 receptors (AT2) were detected in abundance by ex vivo autoradiography. When mesangial cells were isolated from fetal kidney and grown in culture, Ang II type 1 receptors (AT1) were also detected. To explore the mitogenic properties Ang II and fibronectin as well as the effects of Ang II on fibronectin metabolism, studies were performed in vitro, isolated from the potentially confounding variables of hemodynamic influence and circulating growth factors and cytokines. In vitro, mesangial cells expressed a single class of AT1 receptors that were not altered by growth on various substrates. Ang II (10(-7) M) significantly increased thymidine incorporation by confluent human fetal mesangial cells (twofold). When subconfluent, Ang II-stimulated proliferation was greater (fourfold). Ang II significantly increased cell-associated and secreted fibronectin as determined by immunoprecipitation at concentrations that also stimulate mitogenesis. Both of these Ang II-mediated responses were inhibited by the AT1 receptor antagonist DuP-753 (10(-5) M) but not by AT2 receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced beta 1 receptor messenger RNA abundance in the failing human heart

Heart failure in humans is characterized by alterations in myocardial adrenergic signal transduction, the most prominent of which is down-regulation of beta 1-adrenergic receptors. We tested the hypothesis that down-regulation of beta 1-adrenergic receptors in the failing human heart is related to decreased steady-state levels of beta 1 receptor mRNA. Due to the extremely low abundance of beta 1 receptor mRNA, measurements were possible only by quantitative polymerase chain reaction (QPCR) or by RNase protection methods. Because the beta 1 receptor gene is intronless and beta 1 receptor mRNA abundance is low, QPCR yielded genomic amplification in total RNA, and mRNA measurements had to be performed in poly (A)(+)-enriched RNA. By QPCR the concentration of beta 1 receptor mRNA varied from 0.34 to 7.8 x 10(7) molecules/microgram poly(A)(+)-enriched RNA, and the assay was sensitive to 16.7 zeptomol. Using 100-mg aliquots of left ventricular myocardium obtained from organ donors (nonfailing ventricles, n = 12) or heart transplant recipients (failing ventricles, n = 13), the respective beta 1 mRNA levels measured by QPCR were 4.2 +/- 0.7 x 10(7)/micrograms vs. 2.10 +/- 0.3 x 10(7)/micrograms (P = 0.006). In these same nonfailing and failing left ventricles the respective beta 1-adrenergic receptor densities were 67.9 +/- 6.9 fmol/mg vs. 29.6 +/- 3.5 fmol/mg (P = 0.0001). Decreased mRNA abundance in the failing ventricles was confirmed by RNase protection assays in total RNA, which also demonstrated a 50% reduction in beta 1 message abundance. We conclude that down-regulation of beta 1 receptor mRNA contributes to down-regulation of beta 1 adrenergic receptors in the failing human heart.

Renal vascular induction of TGF-beta 2 and renin by potassium depletion

Recently, we have found that transforming growth factor (TGF)-beta 2 and renin are abundantly expressed in the juxtaglomerular apparatus (JGA) of dehydrated mice. Since potassium (K+) depletion also stimulates renin and induces hypertrophy of the JGA, we examined the ability of this maneuver to stimulate TGF-beta isoforms and renin in renovascular tissue and the JGA of young rats. Sprague-Dawley rats (50 +/- 5 g) were fed either a control diet or a potassium-deficient diet (< 0.05% K+) for 7, 16, or 21 days. As a control for TGF-beta and renin stimulation, an additional group of animals was fed a normal diet but was water deprived for three days. Potassium-depleted animals experienced severe growth retardation but kidney weight increased significantly. Potassium depletion induced both TGF-beta 2 and renin immunoreactivity in renal arterioles and the JGA but had no effect on TGF-beta 1 and TGF-beta 3 isoforms. To determine the role of circulating angiotensin II in the stimulation of TGF-beta 2 by potassium depletion, a group of potassium-depleted rats received enalapril (100 mg/liter) in the drinking water. The addition of converting enzyme inhibitor increased both the intensity of TGF-beta 2 and renin staining as well as the number of cells positively stained. Our results demonstrate that K+ depletion induces TGF-beta 2 and renin in renal arterioles and in the JGA. Furthermore, circulating angiotensin II is not responsible for the increase in the local expression of TGF-beta 2. These findings suggest that TGF-beta 2 may be an important mediator of JGA hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective changes in cardiac gene expression during compensated hypertrophy and the transition to cardiac decompensation in rats with chronic aortic banding

Left ventricular hypertrophy (LVH) is associated with reinduction of the fetal program of gene expression. It is unclear whether this pattern of cardiac gene expression changes with the development of left ventricular decompensation and failure. To answer these questions, we quantified steady-state levels of mRNA by the polymerase chain reaction in the left ventricular myocardium of rats 8 and 20 weeks after ascending aortic banding. Clinical and hemodynamic assessment identified two distinct groups of animals 20 weeks after aortic banding. The first group (20-week nonfailed LVH) demonstrated substantial LVH but no depression in systolic developed pressure per gram left ventricular weight compared with the age-matched control group. In contrast, a second group of rats exhibited clinical signs of congestive failure as well as a marked diminution in left ventricular developed pressure per gram. Assessment of the levels of mRNA encoding a panel of cardiac proteins demonstrated a greater than twofold increase in beta-myosin heavy chain mRNA and an approximately sixfold increase in atrial natriuretic factor mRNA in left ventricular myocardium of all three groups (8-week LVH, 20-week nonfailed LVH, 20-week failed LVH) when compared with appropriate age-matched control groups. In contrast, Ca(2+)-ATPase mRNA levels were decreased by 50% only in the left ventricular myocardium of animals with both clinical signs and hemodynamic indexes consistent with cardiac decompensation (20-week failed LVH). These results suggest that in rats with ascending aortic banding the hypertrophic phenotype is associated with a selective reinduction of the fetal gene program, which persists even after the development of left ventricular failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma renin activity as a marker for growth failure due to sodium deficiency in young rats

We evaluated the effect of feeding diets of varying sodium content on growth and plasma renin activity (PRA) in young rats. In the first study, four groups of rats were offered 10 g/100 g body weight per day of diets containing either 0.005%, 0.015%, 0.03%, or 0.3% sodium; weight gain per day of each rat was followed for 10-14 days and PRA was then measured. A control group was fed a sodium-replete tryptophan-deficient diet which caused protein calorie malnutrition and inhibited growth. Weight gain (g/day) among the rats on the sodium-deficient diets varied directly (r = 0.81, P < 0.001) and PRA inversely (r = -0.82, P < 0.001) with dietary sodium content. PRA varied inversely with weight gain (r = -0.84, P < 0.001). Insulin-like growth factor-1 (IGF-1), which is depressed in calorie-deficient growth failure, was depressed in all the rats on the low-sodium intakes relative to ad libitum-fed controls, but did not vary in relation to dietary sodium or weight gain within those groups. In rats fed the tryptophan-deficient diet, both IGF-1 and weight gain were severely depressed; PRA was normal. In the second study, rats in each of two groups were pair fed, the diet containing either 0.03% or 0.3% sodium matched to rats fed the 0.005% sodium diet; weight gain was followed for 28 days. Both length and weight gain were retarded; PRA again varied inversely with dietary sodium content and with weight gain.(ABSTRACT TRUNCATED AT 250 WORDS)

A PCR method for the quantitative assessment of mRNA for laminin A, B1, and B2 chains

Laminin, a basement membrane glycoprotein, is involved in the development of normal kidney and its dysregulation contributes to glomerulosclerosis in renal disease. Studies designed to assess the regulation of this molecule at the level of transcription have been hindered by the relatively low abundance of the mRNA, making standard techniques such as Northern hybridization and RNase protection difficult and inaccurate. In this report, we have utilized the polymerase chain reaction (PCR) to quantitate differences in laminin mRNA expression during normal development of the mouse kidney. We have constructed a synthetic template to be used as an internal standard for mRNA quantitative of laminin chains A, B1 and B2, and beta-actin. This DNA template can be used to generate complementary RNA which can be reverse transcribed and amplified simultaneously with 0.5 microgram of total cellular mRNA allowing for accurate and absolute quantitation of laminin mRNA by PCR.

Reversible alterations in myocardial gene expression in a young man with dilated cardiomyopathy and hypothyroidism

Thyroid hormone effects on myocardial gene expression have been well defined in animal models, but their relationship to the pathogenesis of cardiac dysfunction in hypothyroid humans has been uncertain. We evaluated a profoundly hypothyroid young man with dilated cardiomyopathy. Before and during 9 months of thyroxine therapy, serial assessment of myocardial performance documented substantial improvements in the left ventricular ejection fraction (16-37%), left ventricular end-diastolic diameter (7.8-5.9 cm), and cardiac index (1.4-2.7 liters.min-1.m-2). Steady-state levels of mRNAs encoding selected cardiac proteins were measured in biopsy samples obtained before and after thyroxine replacement. In comparison with myocardium from nonfailing control hearts, this patient's pretreatment alpha-myosin heavy-chain mRNA level was substantially lower, the atrial natriuretic factor mRNA level was markedly elevated, and the phospholamban mRNA level was decreased. All of these derangements were reversed 9 months after restoration of euthyroidism. These observations in an unusual patient with profound myxedema and cardiac dilatation permit correlation between the reversible changes in myocardial function and steady-state mRNA levels in a cardiomyopathy. They suggest that alterations in gene expression in the dilated myopathic heart may be correctable when a treatable cause is identified.

Detection of interleukin and interleukin-receptor mRNA in human heart by polymerase chain reaction

Diminished cardiac contractility associated with inflammatory infiltration may be mediated by the release of interleukins. To test this hypothesis, we assessed the presence of interleukin and interleukin-receptor mRNAs in non-failing human heart and in endomyocardial biopsies from patients with dilated cardiomyopathy or inflammatory myocarditis. Only those interleukins expressed by non-circulating cells (interleukin-1 beta, -4, and -8) were detected in samples of human heart while interleukins specific for activated leukocytes (interleukins-1 alpha and -2) were not detected in any samples. While interleukin-1-receptor mRNA was present in samples from non-failing hearts and those with idiopathic myopathy, it was absent from patients with inflammatory myocarditis, suggesting receptor mRNA down-regulation.

Expression of alpha-subunits of G proteins in failing human heart: a reappraisal utilizing quantitative polymerase chain reaction

A decrease in the density of the beta 1-adrenergic receptor and an increase in the functional activity of the G inhibitory protein Gi accompany human heart failure; however, the molecular and biochemical mechanisms responsible for these changes are unclear. We previously reported that the steady-state levels of the mRNAs encoding both alpha Gi-3 and alpha Gs were significantly increased in failing human heart. However, these results are not consistent with recent studies demonstrating that immunodetectable levels of alpha G proteins are not different in failing human hearts when compared with non-failing controls. In addition, analysis of the 5' flanking regions of alpha Gi and alpha Gs suggests that these two genes are unlikely to be co-regulated as their regulatory domains are quite different. Therefore, we hypothesized that the disparity between the measurements of alpha G protein gene expression and assessment of the actual levels of alpha G proteins might be due to technical limitations of the Northern blot technique utilized in previous studies for assessment of the mRNA levels; (i) cytoskeletal beta-actin mRNA was used as a standard for normalization; and (ii) only relative levels of alpha G mRNAs were measured. The recent application of the polymerase chain reaction to quantification of mRNA levels in small quantities of human heart provided the tool with which to test this hypothesis. When expressed in molecules of mRNA per microgram of total RNA, there were no differences in the levels of alpha Gi and alpha Gs mRNAs in failing human heart when compared with non-failing controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Water deprivation stimulates transforming growth factor-beta 2 accumulation in the juxtaglomerular apparatus of mouse kidney

Transforming growth factor-beta (TGF-beta) modulates the growth and differentiation of many cells and often functions in an autocrine or paracrine fashion. The myoepithelial cells of the renal juxtaglomerular apparatus (JGA) synthesize and secrete renin. Under conditions which chronically stimulate renin production, the JGA undergoes hypertrophy and hyperplasia. The molecular factors responsible for these changes in the JGA have not been identified. In the present study, plasma renin activity was stimulated in the mouse by water deprivation. Using immunoperoxidase staining with specific antibodies against TGF-beta 1, beta 2, and beta 3, we found increased TGF-beta 2 accumulation in the JGA and interlobular arteries. Immunostaining with renin antiserum demonstrated colocalization of TGF-beta 2 and renin. TGF-beta 1 and beta 3 expression was not different between control and water-deprived mice. Our results suggest that in the setting of water deprivation, TGF-beta 2 is localized in a manner which would allow it to act either as a growth factor for or as a phenotypic modulator of the JGA and renal arterioles.

Angiotensin II receptor-mediated proliferation of cultured human fetal mesangial cells

Accumulating evidence suggests that angiotensin II (Ang II) may play an important role in renal growth and glomerular development. During nephrogenesis, a complex relationship between the capillary and renal mesangium develops. Since the mesangial cell is a centrally-located pericyte with contractile, endocrine, and immune modulating functions, it may play a unique role in maintaining normal glomerular function. Therefore, we examined whether Ang II affects proliferation of human fetal mesangial cells in vitro and compared these findings to mesangial cells isolated from adult kidney. In these primary isolates, we studied the relationship between Ang II receptors and the mitogenic activity of angiotensin. Scatchard analysis of the binding of 125I[Sar1,Ile8]Ang II to subconfluent cultured human fetal mesangial cells revealed the presence of one class of binding sites with a Kd of 1.25 nM and a Bmax of 70 fmol/1 x 10(5) cells. Ang II receptors on adult mesangial cells had similar binding kinetics with a Kd of 1.6 nM and Bmax of 65 fmol/10(5) cells in subconfluent culture. In subconfluent culture of fetal mesangial cells, Ang II increased [3H]thymidine incorporation by 130% (P less than 0.005). In subconfluent culture of adult mesangial cells, Ang II increased [3H]thymidine incorporation by only 35% (P less than 0.05). In confluent culture of fetal mesangial cells, Ang II receptor number and mitogenic response were reduced. The Ang II antagonist [Sar1,Ile8]Ang II (1 microM) inhibited the mitogenic response of fetal mesangial cells to Ang II. Ang II increased fetal mesangial cell number by 25% (after 4 days) in serum-free medium supplemented with insulin or supplemented with insulin and 1% Nutridoma (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane stimulates synthesis of extracellular matrix proteins in vitro

The vasoconstrictor eicosanoid thromboxane plays an important role in the pathogenesis of several renal diseases. As an autacoid, its local release alters blood flow and induces platelet aggregation. We report a direct stimulatory effect of thromboxane on extracellular matrix protein production and gene expression in vitro. Treatment of two cell types, differentiated mouse teratocarcinoma cells (F9+) and human glomerular mesangial cells, with two different thromboxane analogues resulted in increased production of components of the extracellular matrix including fibronectin and the basement membrane proteins laminin and type IV collagen. These responses to thromboxane were not the result of a mitogenic effect of thromboxane nor the result of an increase in total cellular protein. The increased production of extracellular matrix proteins was, at least in part, due to an increase in the steady-state level of mRNA for these genes. Furthermore, the effect of thromboxane was markedly inhibited by cotreatment with a thromboxane-receptor antagonist. These results suggest a new potential role for thromboxane as a mediator of the sclerotic and fibrotic responses to injury.

Different effects of chronic K+ depletion on forebrain and peripheral angiotensin II receptors in young rats

K+ depletion stimulates the circulating renin-angiotensin system and affects the regulation of peripheral angiotensin II receptors. The effects of K+ depletion on the regulation of central angiotensin II receptors are unknown. We studied the effects of selective K+ depletion (less than 0.05% in diet for 16 days) on angiotensin II receptor number in kidneys, adrenal glands, and selected brain areas of young rats. K+ depletion caused a significant increase in plasma renin activity and significantly decreased angiotensin II receptor number in the kidney glomeruli and medulla, and in the adrenal zona glomerulosa and adrenal medulla. In the brain, the angiotensin II receptor number was unchanged in the subfornical organ and the hypothalamic paraventricular nucleus after 16 days of K+ depletion. An additional NaCl supplementation (0.02% in the drinking water) to K(+)-depleted rats produced a decrease in plasma renin activity but failed to affect subfornical organ or paraventricular angiotensin II receptor number. Our results suggest that in young animals, K+ depletion has a significant impact on the peripheral renin-angiotensin system without affecting the density of forebrain angiotensin II receptors.

Selective gene expression in failing human heart. Quantification of steady-state levels of messenger RNA in endomyocardial biopsies using the polymerase chain reaction

BACKGROUND

Evaluation of gene expression in failing human heart has been limited by the availability of cardiac tissue.

METHODS AND RESULTS

We used the polymerase chain reaction (PCR) to assess gene expression in small quantities of failing and nonfailing human heart. PCR is a powerful new molecular biological tool that allows a small quantity of DNA to be amplified as much as 1 million-fold. Total RNA was extracted from 3-5 mg samples of human heart and reverse-transcribed to complementary DNA (cDNA). With selected oligonucleotide primers, we used PCR to amplify cDNAs encoding atrial natriuretic peptide, beta-myosin heavy chain, phospholamban, and cytoskeletal beta-actin. To quantify the relative levels of messenger RNA (mRNA) in human heart, a known amount of a control RNA was present in the reverse transcription and PCR reactions. The amount of mRNA in the sample could therefore be assessed in relation to the amount of control product. The control RNA was transcribed from a synthetic DNA template containing primers complementary to those used to amplify the cDNAs of interest. Atrial natriuretic factor mRNA could not be detected in nonfailing human heart but was abundant in ventricular myocardium from failing human heart. In contrast, steady-state levels of phospholamban mRNA decreased, whereas levels of beta-myosin heavy-chain mRNA were unchanged with heart failure.

CONCLUSIONS

Alterations in gene expression in the failing human heart appear to be selective. In addition, the present study suggests that PCR provides a rapid and economical way to quantify the expression of multiple genes of interest in endomyocardial biopsy specimens and may therefore be used to advance our understanding of heart muscle disease.

Chronic sodium or chloride depletion upregulates angiotensin II receptors in the anterior pituitary lobe of young rats

The effect of chronic (35 days) and selective sodium or chloride depletion on the regulation of angiotensin II receptors in the anterior pituitary gland of young male rats was studied by quantitative autoradiography. Both chronic sodium or chloride depletion produced significant extracellular fluid volume contraction, stimulation of the circulating renin-angiotensin system and increased the number of angiotensin II receptors in the anterior pituitary gland. Changes in angiotensin II receptors in both sodium- and chloride-depleted animals were associated with increased plasma prolactin levels. Our results suggest a participation of the pituitary renin-angiotensin system in the physiological response and/or possible adaptation to chronic sodium or chloride depletion. Extracellular fluid volume contraction and profound chronic stimulation of the circulating renin-angiotensin system may contribute to regulate anterior pituitary angiotensin II receptors and may influence prolactin release.

Effects of reduced renal function and dietary protein on muscle protein synthesis

We describe a rat model of renal failure that separates catabolic and anabolic states from each other. Muscle protein synthesis was compared during the anabolic period between sham (S) operated and renal failure (RF) rats that were fed different levels of dietary protein. Male rats weighing between 60 and 80 g first had a partial left nephrectomy and then were given a tryptophan deficient diet from four to six days to induce weight loss. On the second day of the diet either a renal decapsulation (S rats) or a simple right nephrectomy (RF rats) was done to enhance the catabolic response in both and to induce renal failure in the RF rats. Following the period of feeding the deficient diet, both groups were fed a nutritionally complete 14, 17, 20 or 30% protein diet for three to five days. This induced a brisk anabolic response as measured by weight gain. Differences in body weight between the S and RF rats after three to five days on the repletion diet generally was less than 10%. The rats then were fasted overnight, fed a standard meal and muscle protein synthesis (Sm%) was measured two hours post-feeding. Sm% was estimated from the incorporation of 3H phenylalanine (PHE) into muscle 10 minutes following the i.v. injection of 3HPHE (25 muCi/100 g body wt) with carrier PHE to flood all the precursor amino acid pools. Weight loss in the catabolic phase was greater and the net weight gain for the two phases was less in the RF group. Overall, renal failure resulted in a significant reduction in Sm% (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Different effects of chronic Na+, Cl-, and K+ depletion on brain vasopressin mRNA and plasma vasopressin in young rats

1. We studied the effects of selective chronic dietary sodium, chloride, or potassium depletion in young rats on vasopressin mRNA levels in the supraoptic and paraventricular nuclei, an index of vasopressin formation, and in plasma vasopressin levels, an index of vasopressin release. 2. All diets significantly increased plasma renin activity, contracted the extracellular fluid volume, and decreased serum osmolarity. 3. In the supraoptic nucleus, vasopressin mRNA levels were significantly decreased in the low-sodium group but were not significantly affected by chloride depletion. 4. There were no significant changes in vasopressin mRNA in the paraventricular nucleus after sodium or chloride dietary depletion. 5. After 2 weeks of potassium depletion, vasopressin mRNA levels were decreased in the supraoptic nucleus. When potassium depletion was prolonged for 3 weeks, vasopressin mRNA levels increased in both supraoptic and paraventricular nuclei. 6. Plasma vasopressin levels were high in animals subjected to dietary chloride depletion or to 3 weeks of potassium depletion. Dietary sodium depletion or 2 weeks of dietary potassium depletion did not significantly affect plasma vasopressin. 7. Our results show that chronic sodium, chloride, or potassium depletion differentially affect brain vasopressin mRNA and vasopressin release in young rats. 8. The effect of these diets may be mediated through changes in the extracellular fluid volume, serum osmolarity, and/or renin angiotensin system.

Different effects of sodium or chloride depletion on angiotensin II receptors in rats

We studied the effects of selective chronic sodium or chloride depletion (0.005% in diet) on central and peripheral angiotensin II receptors in young rats. Chloride depletion produced the most significant increase in plasma renin activity and extracellular fluid volume contraction. In the brain, subfornical organ angiotensin II receptor concentration was decreased by sodium depletion and increased by chloride depletion. There were no significant changes in angiotensin II binding in the paraventricular nucleus. When sodium-depleted rats were water deprived for 3 days, subfornical organ angiotensin II receptor concentration increased, showing that normal sodium intake was not essential for increased numbers of angiotensin II receptors during dehydration. In the adrenal gland, chloride depletion decreased angiotensin II receptors in the medulla and zona glomerulosa. Conversely, sodium depletion increased angiotensin II receptors in the zona glomerulosa. In the kidney glomeruli and medulla, angiotensin II receptors were decreased by either sodium or chloride depletion. These results suggest different roles for sodium and chloride in the regulation of the peripheral and central renin-angiotensin system in young rats.

Down-regulation of angiotensin II receptors in subfornical organ of young male rats by chronic dietary sodium depletion

The effect of a 4-week period of selective dietary sodium depletion on the regulation of peripheral and central angiotensin II receptors was studied in young rats, by quantitative autoradiography. Moderate sodium depletion (0.05% sodium in diet) significantly impaired growth rate and stimulated the renin-angiotensin system, but did not result in significant changes in peripheral or central angiotensin II receptors. In young rats, the impairment of the growth rate and the stimulation of the peripheral renin-angiotensin system were more notable after profound sodium depletion (0.005% sodium in diet). Such sodium depletion corresponded to a down-regulation of kidney angiotensin II receptors, and to an up-regulation of adrenal zona glomerulosa angiotensin II receptors. These effects are similar to those reported in adult rats. In the brain, profound sodium depletion down-regulated angiotensin II receptors in the subfornical organ. There were no changes in angiotensin II receptors in another brain structure, the paraventricular nucleus. Our results indicate a participation of selective central angiotensin II receptors in the regulation of sodium metabolism and suggest that factors other than circulating angiotensin II levels might contribute to regulate the number of angiotensin II receptors in the subfornical organ.

Amplification and molecular cloning of HTLV-I sequences from DNA of multiple sclerosis patients

Techniques of gene amplification, molecular cloning, and sequence analysis were used to test for the presence of sequences related to human T-lymphotropic virus type I (HTLV-I) in peripheral blood mononuclear cells of six patients with multiple sclerosis (MS) and 20 normal individuals. HTLV-I sequences were detected in all six MS patients and in one individual from the control group by DNA blot analysis and molecular cloning of amplified DNAs. The viral sequence in MS patients were associated with adherent cell populations consisting predominantly of monocytes and macrophages. Molecular cloning and nucleotide sequence analysis indicated that these amplified viral sequences were related to the HTLV-I proviral genome.

Growth rate in infants with impaired renal function

We report changes in renal function and growth rate in children with reduced renal function who were kept on a low normal phosphorus formula until 18 months of age. The relationship between serum creatinine values and derived creatinine clearance and residual renal function is reviewed regarding the risk of progressive loss of function. Expressing growth as growth velocity standard deviation scores over 6-month intervals gave a more accurate description of growth performance than did change in height standard deviation scores. A relationship between residual clearance and growth velocity was inferred. However, the growth of children with a less severe reduction in function was affected intermittently by intercurrent infections and inadequately treated acidosis and salt wasting. Children with a more severe reduction in function, despite maintenance on the low-phosphorus formula, had elevated serum parathormone levels. We conclude that following growth (as serial growth velocity standard deviation scores) in relation to other variables gives more insight into factors affecting growth in these children; the level of residual function affects growth potential but other complicating factors also have an effect.

Naproxen nephrotoxicity in a 2-year-old child

The development of acute renal failure and interstitial nephritis due to therapeutic doses of nonsteroidal anti-inflammatory drugs has been documented repeatedly in adult patients but is rare in children. We report the occurrence of this complication in a child. Acute renal failure and hyperkalemia developed in a 2-year-old boy with juvenile rheumatoid arthritis after one month of naproxen sodium therapy. The evidence of renal toxic effects became manifest after an episode of dehydration. A percutaneous renal biopsy specimen revealed interstitial nephritis. The patient recovered promptly after withdrawal of the drug.

Qualitative evaluation of the reagin screen test

After a preliminary study of 557 sera used as a procedural training exercise, the Reagin screen test (RST) for the macroscopic detection of reagin (as an aid to detecting syphilis) was qualitatively compared to the rapid plasma Reagin (RPR) (circle) card test and Veneral Disease Research Laboratory (VDRL) slide test on 435 random portions of sera using fluorescent treponemal antibody adsorption (FTA-ABS) results as a comparative base. A comparison of total agreement (positive and negative) with the FTA-ABS results led to the following order. RPRCT (I5.5%), VDRL (79.8%), and RST (74.5%). Of the total samples shown to be reactive by the FTA-ABS procedure, the percentage of these interpreted as nonreactive (i.e., "false negative") by the procedures compared was considerably higher with the RST procedure (29.3%) than with either the RPRCT (10.9%) or the VDRL (7.1%) procedures. Minor problems encountered with procedural techniques are also mentioned.