Plasma disappearance of rabbit α2 HS-glycoprotein and its uptake by bone tissue

Summary Plasma ₂HS-glycoprotein is specifically accumulated in calcified tissues. In the present studies this glycoprotein was isolated from plasma and after iodination with iodine-125 was injected intravenously into young rabbits. The tissue distribution and plasma disappearance rate of this radioactively labeled material were determined. Of the various tissues studied, bone showed the greatest retention of labeled glycoprotein expressed as percentage of the injected dose per gram tissue relative to the plasma content.The rate of loss of iodinated ₂HS-glycoprotein from plasma was similar to that of ₂HS-glycoprotein labeled endogenously by using¹⁴C-glucosamine or³H-glucosamine. The uptake of exogenously labeled³I- ₂HS-glycoprotein into bone tissue expressed as a percentage of the injected dose was similar to that of endogenously labeled¹⁴C- ₂HS-glycoprotein. These results suggest that the¹²⁵I-labeled material can be used to study further the metabolism of ₂HS-glycoprotein by bone tissue.     

Role of inter-α-inhibitor and its related proteins in experimentally induced calcium oxalate urolithiasis. Localization of proteins and expression of bikunin gene in the rat kidney

Summary Our earlier studies indicated that members of the inter-α-inhibitor (IαI) family of glycoproteins may play an important role in urolithiasis. Indeed bikunin, the light chain of IαI is a potent inhibitor of calcium oxalate crystallization. In order to understand this role, the distribution of IαI and its related proteins, as well as the expression of bikunin, were studied in normal and nephrolithic rats. In normal rats, IαI immunoreactivity was located mainly in proximal tubules. However, in nephrolithic rats, in addition to proximal tubules, the staining was intensively extended to tubules in the corticomedullary junction. Furthermore, by using polymerase chain reaction technique, we demonstrated that gene encoding for bikunin was activated in kidneys of nephrolithic rats. We have previously demonstrated increased staining for osteopontin in association with calcium oxalate crystal deposition in rat kidneys. Others have shown an increase in osteopontin production by renal epithelial cells on exposure to calcium oxalate crystals. Based on these observations we conclude that kidney cells possess an auto-defense system against calcium oxalate crystallization and stone formation in which members of the IαI family may be closely involved. Received: 18 February 1998 / Accepted: 9 July 1998     

Enhanced Bruton’s tyrosine kinase activity in the kidney of patients with IgA nephropathy

International Urology and Nephrology - Bruton’s tyrosine kinase (BTK) is a vital biological molecule that contributes to immune regulation. Previous studies have showed that BTK can be...     

Plasma proteins present in human cortical bone: Enrichment of theαHS-glycoprotein

The spectrum of plasma proteins present in human cortical bone and permanent dentine has been determined. One plasma glycoprotein, theHS-glycoprotein, was found to be present at a high concentration in both bone and dentine and was shown to be concentrated in the mineralized tissues with respect to the other plasma proteins by factors of between 30 and 100. In this respect theHS-glycoprotein is analogous to the G2B-glycoprotein and -glycoprotein of bovine and rabbit b one, respectively. The binding ofHS-glycoprotein and albumin to calcium phosphates generated within serum samples has been studied at different serum: precipitate ratios. In each case all theHS-glycoprotein was removed from the samples and theHS-glycoprotein was concentrated with respect to albumin by factors ranging from 370 at the highest serum: precipitate ratio to 25 at the lowest ratio. The plasmaHS-glycoprotein concentrations of patients with Paget's disease of bone were shown to be substantially lower than the normal range, with significant negative correlation between theHS-glycoprotein concentration and the plasma alkaline phosphatase activity.     

Increased α1D adrenergic receptor activity and protein expression in the urinary bladder of aged rats

Objectives  A possibility that aging affects (a) expression of the α1D-adrenergic receptor (AR1D), (b) AR1D-mediated contractions and (c) sympathetic innervation in the urinary bladder in rats was studied. Materials and methods  Contraction produced by phenylephrine and inhibition of these contractions by a non-selective α1-adrenergic antagonist prazosin and a selective AR1D antagonist BMY7378 were compared between 6- and 24-month-old Fisher rats. Expressions of VMAT and AR1D in the bladder were assessed by immunofluorescence and Western blot. Results  Phenylephrine-induced contractions were larger and inhibition of these contractions by BMY7378 was significantly greater in 24-month-old rats. Aging increased expression of AR1D in the bladder. Density of VMAT-immunoreactive neurites was decreased in smooth muscle but elevated in the suburothelial region of 24-month-old rats. Conclusions  The results suggest that influence of adrenergic activity on bladder contractility increases with aging is due to overexpression of the AR1D. Influence of adrenergic activity on the urothelial function may also be enhanced with aging.     

Role of the kidney in acid–base balance

Correction of disturbances in acid–base balance is achieved by: physicochemical buffering by extracellular and intracellular buffer systems (instantaneous), alveolar ventilation to control pCO₂ (rapid), and renal compensation (long term). Buffering and changes in ventilation limit changes in pH, but cannot return acid–base status to normal. The kidney has a pivotal role: disturbances can be completely corrected through changes in H⁺ secretion and HCO₃^? reabsorption and production. HCO₃^? reabsorption is modified by changes in glomerular filtration rate (filtered load), changes in extracellular volume and by hormones which modify Na⁺ reabsorption via the Na⁺–H⁺ exchanger in renal tubular cells. Changing the activity of this exchanger influences H⁺ secretion and, hence, HCO₃^? reabsorption. Chronic (but not acute) changes in pCO₂ influence HCO₃^? reabsorption through changes in the filtered load and, in chronic acidosis, by the insertion of more H⁺ transport proteins in renal tubular cells. Renal HCO₃^? production is linked to H⁺ excretion: acid buffer salts (phosphate, creatinine), their availability and pK and tubular fluid pH. Formation and excretion of NH₄⁺ buffer salts are important – acidosis stimulates secretion of NH₄⁺ (proximal tubule) and NH₃ (collecting duct). There is a reciprocal relationship between extracellular K⁺ and NH₄⁺ excretion, hence HCO₃^? production.     

Functional relationship of α-glutathione S-transferase and glutathione S-transferase activity in machine-preserved non-heart-beating donor kidneys

alpha-Glutathione S-transferase (alpha-GST) is a biochemical parameter used to estimate the amount of proximal tubule damage to a kidney. In normal clinical practice, the concentration of alpha-GST in urine is determined by a rather time-consuming immunochemical test, the enzyme-linked immunosorbent assay (ELISA). Kidneys from non-heart-beating (NHB) donors are perfused prior to transplantation. The determination of alpha-GST concentration in the perfusate to monitor damage is also done by means of an ELISA test. However, because this is a time-consuming method, it would be helpful to find a parameter proportional to GST concentrations that would be available within minutes. We therefore compared the method of determining alpha-GST concentration via ELISA with that of determining the enzymatic activity of GST, which is much faster (results available within 10 min). The comparison was made using 150 preserved kidneys that had been perfused for 6 h. The correlation was found to be very good, as indicated by the linear regression data: r=0.954, P<0.001. pi-Glutathione S-transferase (pi-GST) was also determined by means of an ELISA test, and the concentration of pi-GST was compared with the enzymatic activity of the "total" GST. The precision of the enzymatic method, given by intra- and interassay variation, was 1.5% and 10.5%, respectively.     

Nephrocystin and ciliary defects not only in the kidney?

Cystoproteins have been recognized to play a major role in the development of cystic kidney diseases (CKDs) via interaction with the cilia/centrosome complex. We highlight our present knowledge on nephrocystin as the defective protein in nephronophthisis type I. Nephrocystin has been localized to the ciliary transition zone not only of renal tubule cells but also of respiratory and retinal cilia. Thus, multi-system involvement as in Senior–Løken-syndrome (retinal degeneration plus nephronophthisis) can be explained by a functional ciliary defect in various tissues. In addition, we illustrate that ciliated respiratory cells have a high potential for diagnostics in CKDs and will further aid understanding of the underlying molecular mechanisms.     

Complete absence of the αGal xenoantigen and isoglobotrihexosylceramide in α1,3galactosyltransferase knock-out pigs

Puga Yung GL, Li Y, Borsig L, Millard A‐L, Karpova MB, Zhou D, Seebach JD. Complete absence of the αGal xenoantigen and isoglobotrihexosylceramide in α1,3galactosyltransferase knock‐out pigs. Xenotransplantation 2012; 19: 196–206. © 2012 John Wiley & Sons A/S. Abstract: Background: Anti‐Galα1,3Galβ‐R natural antibodies are responsible for hyperacute rejection in pig‐to‐primate xenotransplantation. Although the generation of pigs lacking the α1,3galactosyltransferase (GalT) has overcome hyperacute rejection, antibody‐mediated rejection is still a problem. It is possible that other enzymes synthesize antigens similar to Galα1,3Gal epitopes that are recognized by xenoreactive antibodies. The glycosphingolipid isoglobotrihexosylceramide (iGb₃) represents such a candidate expressing an alternative Galα1,3Gal epitope. The present work determined whether the terminal Galα1,3Gal disaccharide is completely absent in Immerge pigs lacking the GalT using several different highly sensitive methods. Methods: The expression of Galα1,3Gal was evaluated using a panel of antibodies and lectins by flow cytometry and fluorescent microscopy; GalT activity was detected by an enzymatic assay; and ion trap mass spectroscopy of neutral cellular membranes extracted from aortic endothelial was used for the detection of sugar structures. Finally, the presence of iGb₃ synthase mRNA was tested by RT‐PCR in pig thymus, spleen, lymph node, kidney, lung, and liver tissue samples. Results: Aortic endothelial cells derived from GalT knockout pigs expressed neither Galα1,3Gal nor iGb₃ on their surface, and GalT enzymatic activity was also absent. Lectin staining showed an increase in the blood group H‐type sugar structures present in GalT knockout cells as compared to wild‐type pig aortic endothelial cells (PAEC). Mass spectroscopic analysis did not reveal Galα1,3Gal in membranes of GalT knockout PAEC; iGb₃ was also totally absent, whereas a fucosylated form of iGb₃ was detected at low levels in both pig aortic endothelial cell extracts. Isoglobotrihexosylceramide 3 synthase mRNA was expressed in all pig tissues tested whether derived from wild‐type or GalT knockout animals. Conclusions: These results confirm unequivocally the absence of terminal Galα1,3Gal disaccharides in GalT knockout endothelial cells. Future work will have to focus on other mechanisms responsible for xenograft rejection, in particular non‐Galα1,3Gal antibodies and cellular responses.     

Can the kidney function as a lung? Systemic oxygenation and renal preservation during retrograde perfusion of the ischaemic kidney in rabbits

OBJECTIVE: To investigate renal preservation by a novel method of perfusion using an oxygenated perfluorocarbon (PFC) emulsion via retrograde access to the kidney, as preserving renal function during urological surgery has been elusive, and the recognized technique of nephron-sparing surgery has increased its application and practice in modern urology. MATERIALS AND METHODS: After institutional review and approval, 30 New Zealand White rabbits were studied. In a solitary kidney model, each rabbit had the ureter catheterized before 40 min of renal artery occlusion. Each rabbit was randomized to one retrograde perfusion group, i.e. sham, normothermic PFC, chilled PFC, normothermic saline, and chilled saline. The rabbits were maintained for 2 weeks, during which renal function, urine output, systemic blood gases, weight and serum creatinine level were measured. After death, the kidneys were individually examined and graded by one renal pathologist unaware of the treatment. RESULTS: The rabbits treated with retrograde PFC perfusion (normothermic and chilled) had less change in their creatinine clearance, at 3.6 and 4.0 mL/min per kg, than the sham group, at 7.8 mL/min per kg, while also having significantly higher systemic venous oxygenation, at 26.3 and 10.0 mmHg, than the sham group, at 0.2 mmHg. Normothermic and chilled perfusion with PFC was also associated with less histological evidence of ischaemic damage, with mean (sd) scores of 13.0 (13.5) and 8.7 (4.5), respectively, than in the sham group, at 33.3 (16.8), while favourably matching the contralateral control kidney group, at 5.5 (2.3). The rabbits treated with saline retrograde perfusion also had better outcomes than the sham cohort. There were no adverse effects in any of the study arms or with the use of PFC. CONCLUSION: Retrograde oxygen delivery to the kidney through the urinary collecting system was successful in this pilot study. Renal function, laboratory and histological data indicate a trend towards renal preservation and even systemic oxygenation in the experimental groups compared with the sham rabbits, with no adverse effects attributed to this technique.     

Uninephrectomy increases kidney beta2-microglobulin: can it play a role in the progression of kidney damage?

Beta2-microglobulin (beta2M) is highly accumulated by the kidneys of normal rats. The aim of this study was to verify if uninephrectomy can modify the renal uptake of labeled beta2M. For this purpose the radioactivity of plasma and those of the remaining kidney, liver and urine have been measured in uninephrectomized rats (NX) and in controls (C) at different times after the injection as i.v. bolus of 131I-beta2M. The experiments were performed in 114 Sprague-Dawley male rats. Fifty seven animals underwent right nephrectomy, the other animals being the C. NX and their C were divided in 3 groups, studied 2, 4 and 6 weeks after nephrectomy, respectively. Part of the animals were sacrificed 12 min after the injection of labeled beta2M (peak-time, i.e. time of highest kidney accumulation of 131I-beta2M in the normal rat) and part 10 min later. The results demonstrate that: - uninephrectomy increases plasma retention of 131I-beta2M - kidney uptake (total and per gram) is always higher in NX - liver uptake (much lower than that of kidney) is not influenced by uninephrectomy - urine excretion of radioactivity is minimal in both NX and C. The behavior of beta2M is similar to that we previously observed with alpha1-microglobulin and lysozyme. The higher kidney content of some low mw proteins after uninephrectomy could play a role in the progressive reduction of renal function determined by the reduction of renal mass.     

Obesity and the kidney: Why is the kidney at risk?

Two recent studies may help to account for the increase in risk of renal injury associated with obesity. One study pointed to a role for renin-system activation. In the other study, the pattern of renal hemodynamics was compatible with a renin mechanism.