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At least 721 records · Page 40Linked to original sources
PubMed1973

The action of bombesin on the kidney of the anaesthetized dog.

1. In the anaesthetized dog bombesin had a potent antidiuretic effect, and sometimes arrested urine flow completely. Threshold doses, by i.v. infusion, were of the order of 0.5-1 (ng/kg)/minute. Antidiuresis was the result of a reduction in glomerular filtration rate provoked by a fall in intraglomerular hydrostatic pressure. This, in its turn, was due to afferent vasoconstriction.2. The spasmogenic effect of bombesin on the smooth muscle of the afferent arterioles was directly demonstrated by the radioactive microspheres technique and indirectly by the (85)Kr washout method and by [(3)H]-p-aminohippurate clearance. The vascular compartment most sensitive to bombesin was that of the outer cortical zone, especially in its external half.3. Filtration fraction decreased under the influence of bombesin, indicating that the effect of the polypeptide on postglomerular arterioles was, if present, only of minor importance.4. At high infusion rates (above 6 (ng/kg)/min), bombesin produced a decrease in [(3)H]-p-aminohippurate extraction. The effect of the polypeptide on fractional distal delivery of sodium varied with the dose: at moderate infusion rates it decreased, at high infusion rates it increased. The total glucose appearing in urine following a glucose load was sharply reduced by bombesin. However, the glomerular filtration rate/maximum tubular glucose transport ratio did not show any appreciable change.5. Afferent vasoconstriction produced by bombesin was accompanied by an intense activation of the renin-angiotensin system, as shown by a conspicuous increase in renin secretion, followed by increases in renin activity and angiotensin II concentration in arterial blood. When bombesin was infused into one renal artery only the infused kidney showed afferent vasoconstriction and increased renin secretion. The time-course of renin secretion produced by bombesin depended upon the rate of infusion of the polypeptide. At low rates an increased renin secretion was observed throughout the infusion period, at high rates two peaks of renin secretion could be seen, one at the beginning of the infusion, the other soon after the infusion had finished.6. The mechanism of action of bombesin is discussed and the interest of the polypeptide as a possible hormonal regulator of the circulation and function of the kidney is pointed out.

Anesthesia, General↗
PubMed2004

Evaluation of the nitric oxide production in rat renal artery smooth muscle cells culture exposed to radiocontrast agents.

BACKGROUND: Radiocontrast agents (RC), substances largely used in diagnostic procedures, present the nephrotoxicity as one of its major side effects, which could be due to an altered synthesis of vasodilators. The aim of the present study was to evaluate the nitric oxide (NO) production in rat renal artery smooth muscle cells primary culture (rVSMC) exposed to RC. METHODS: The cells were treated for 72 hours with mannitol at 10% (MT10; 600 mOsm/kg H2O) or 35% (MT35; 2100 mOsm/kg H2O), with the nonionic iobitridol (IBT), the low-osmolality ioxaglate (IXG), the high-osmolality ioxitalamate (IXT), the nonionic, iso-osmolar iodixanol (IDX), and with lipopolysaccharide (LPS). We determined the NO and osmolality in the cell culture media and the cellular viability. RESULTS: By the Griess and chemiluminescence methods, the NO was not different in MT10 and IDX, but decreased in MT35, IBT, IXG, and IXT when compared with the control; it was increased in LPS and also decreased in all RC+LPS when compared with LPS. MT35, IXT, and IXT+LPS decreased the cellular viability, and the media osmolality was increased in MT35 and IXT compared with the control. CONCLUSION: The RC (except IDX) significantly reduced NO in rVSMC, which was more pronounced after IXT treatment (57.3%). This was not related to the reduced cell viability (15.8%) or to its high osmolality, because in MT35, with similar osmolality as IXT, NO decreased only 11.0% relatively to the control. Neither the media osmolality nor the cell viability was altered by IXG or IBT. The decreased NO could explain the vasoconstriction and, therefore, the acute renal failure by RC.

Animals↗
PubMed2005

Simultaneous determination of anions in nanoliter volumes.

BACKGROUND: The study of renal tubular transport requires the ability to accurately measure ion concentrations in samples taken from single tubules. Sample collection and analysis are laborious, so methods allowing determination of multiple ion species in a small volume sample are advantageous. This article describes a method for the simultaneous analysis of anions at physiologic concentrations in nanoliter volumes of tubular fluid. METHOD: The analysis is performed using capillary zone electrophoresis. Diluted samples are moved along a capillary by bulk transport and separated according to charge and size. Peaks corresponding to anions are obtained by ultraviolet (UV) detection; peak area is proportional to ion concentration. RESULTS: The anions chloride, nitrate, citrate, phosphate, and bicarbonate were separated in less than 4 minutes, and iothalamate in less than 5 minutes. Simultaneous quantitative analysis was performed for chloride, phosphate, and bicarbonate, demonstrating detection limits of 12 fmol for chloride, 12 fmol for phosphate, and 72 fmol for bicarbonate. A comparison between this method and a flow-through microfluorimeter analysis of chloride showed good agreement between the two micro-methods. Illustrative data from proximal and distal tubular fluid samples obtained by micropuncture (volume 30-70 nL) are given, as are results from urine samples. RESULTS: Results for chloride, phosphate, and bicarbonate in control material are in close agreement with the certified values, while values in tubular fluid are in accordance with previously published results. CONCLUSION: This method provides a straightforward means of analyzing multiple anions in small volume biological samples.

Animals↗
PubMed2005

Up-regulation of HIF in experimental acute renal failure: evidence for a protective transcriptional response to hypoxia.

BACKGROUND: Medullary hypoxia is believed to play an important role in the pathogenesis of acute renal failure (ARF). Hypoxia-inducible transcription factors (HIF) are recognized as master regulators of hypoxic adaptation, but little is known about their role in renal disease. METHODS: A multi-insult rat model of ARF combining the application of contrast medium with nitric oxide synthase (NOS) and cyclooxygenase (COX) inhibition was used to study chronology and distribution of the oxygen regulated HIF isoforms HIF-1alpha and HIF-2alpha in comparison with the hypoxia-marker pimonidazole between 10 minutes and 48 hours after injury induction. Treatment with furosemide was used to study HIF expression under conditions of ameliorated tissue injury. RESULTS: Contrast medium in combination with NOS and COX inhibition resulted in widespread induction of HIF in the outer and inner medulla that was initiated within 10 minutes, reached the highest levels at 2 hours and diminished 8 hours to 24 hours thereafter. HIF isoforms were expressed in a cell type-specific fashion: HIF-1alpha in tubular and HIF-2alpha in interstitial and endothelial cells. The degree of HIF-1alpha accumulation varied between nephron segments, being much stronger in collecting ducts than in medullary thick ascending limb of the loop of Henle (mTAL). Comparison with pimonidazole staining and the effect of furosemide indicated that HIF induction in mTAL is maximal with moderate hypoxia and declines with increasing severity of hypoxia. CONCLUSION: A complex pattern of HIF activation appears to play an important role in tissue preservation as a response to regional renal hypoxia. The limited capacity of mTAL cells for HIF activation may explain their susceptibility to injury.

Acute Kidney Injury↗