Creatinine Transport Research Articles

Transport of sodium chloride, urea, and creatinine through membranes derived from methylmethacrylate‐co‐methacrylic acid and its ionomers

AbstractPermeabilities of cast films of methylmethacrylate‐co‐methacrylic acid (MMA—MAA) and its 5% neutralized Na1+, CS1+, Zn2+, Ba2+, and Al3+ ionomers for urea, sodium chloride, and creatinine were determined using a double (donor and acceptor) compartment cell. Film permeability was increased as the ionic potential decreased and it was more marked with urea as compared with sodium chloride and creatinine. Tensile properties of the above samples were also tested and variations in Young's Moduli were based on the effect of type of aggregates produced by the cations in the matrix of the copolymer. © 1993 John Wiley & Sons, Inc.

Effect of uremia on the membrane transport characteristics of red blood cells

Even though there is extensive evidence that uremia affects the fragility and deformability of red blood cells (RBCs), essentially all data on the RBC membrane permeability have been obtained with nonuremic blood. Permeability data were obtained for creatinine and uric acid, two metabolites of interest in hemodialysis, using a stirred ultrafiltration device with direct cell- and protein-free sampling. Experiments examined the effects of temperature and suspending phase on solute transport for both normal and uremic blood cells. Creatinine and uric acid transport from normal RBCs at 37 degrees C were characterized by saturation half-times of 40 +/- 10 minutes and 54 +/- 12 minutes, respectively. The corresponding half-times for uremic cells were significantly longer, 94 +/- 26 minutes and 180 +/- 38 minutes. Data indicated that the slower rate of creatinine transport in uremic blood was caused by an alteration in the RBC membrane, while the reduction in uric acid transport was associated with alterations in the uremic plasma. The temperature dependence of the RBC permeability was also much less pronounced for uremic cells for both solutes. These results provide important insights into the effects of uremia on the RBC membrane permeability, and have important implications for dialysis.

Effect of Uremia on the Membrane Transport Characteristics of Red Blood Cells

Even though there is extensive evidence that uremia affects the fragility and deformability of red blood cells (RBCs), essentially all data on the RBC membrane permeability have been obtained with nonuremic blood. Permeability data were obtained for creatinine and uric acid, two metabolites of interest in hemodialysis, using a stirred ultrafiltration device with direct cell- and protein-free sampling. Experiments examined the effects of temperature and suspending phase on solute transport for both normal and uremic blood cells. Creatinine and uric acid transport from normal RBCs at 37 degrees C were characterized by saturation half-times of 40 +/- 10 minutes and 54 +/- 12 minutes, respectively. The corresponding half-times for uremic cells were significantly longer, 94 +/- 26 minutes and 180 +/- 38 minutes. Data indicated that the slower rate of creatinine transport in uremic blood was caused by an alteration in the RBC membrane, while the reduction in uric acid transport was associated with alterations in the uremic plasma. The temperature dependence of the RBC permeability was also much less pronounced for uremic cells for both solutes. These results provide important insights into the effects of uremia on the RBC membrane permeability, and have important implications for dialysis.

Simple membrane models for peritoneal dialysis. Evaluation of diffusive and convective solute transport.

Currently used mathematical models to estimate parameters describing diffusive (diffusive mass transport coefficient, KBD) and convective (sieving coefficient, S) solute transport during peritoneal dialysis, as proposed by Pyle, Popovich, and Moncrief (PPM model) and Babb, Randerson, and Farrell (BRF model), require nonlinear regression and advanced numerical methods for parameter estimation. In this study, a simplified approach to the evaluation of KBD and S, using the same transport equation used in the PPM and BRF models but based on two-dimensional linear regression, is proposed. This new approach can be extended to generate a family of membrane models that differ in assumption concerning the average solute concentration (c) inside the peritoneal membrane. In particular, c was assumed to be equal to the arithmetic mean value of the dialysate and blood concentrations (PPM model), the blood concentration (BRF model), or the dialysate concentration (D model). The investigated family of models was used to study the transport of urea, creatinine, glucose, sodium, potassium, and total protein in 20 single, 6 hr dwell studies carried out in 20 nondiabetic patients in stable clinical condition using hypertonic (3.86%) glucose solution. For the PPM model, the linear and nonlinear regressions were able to provide almost identical values of KBD and S. The theoretical dialysate to plasma concentration ratio (D/P) was adequately fitted to experimental D/P for both the PPM and BRF models, but the fit was worse for the D model. However, unphysiologic (i.e., out of the 0-1 range) values of S were found for urea, potassium, and glucose independent of the version of the model used.

Visceral peritoneum is not essential for solute transport during peritoneal dialysis

The importance of visceral peritoneum in determining transperitoneal solute exchange was studied by determining the influence of evisceration on diffusive solute transport during peritoneal dialysis. Three series of experiments were performed in anesthetized New Zealand White rabbits. Series 1 studies compared solute transport rates from eviscerated rabbits (N = 5) with those from sham-operated controls (N = 5). Series 2 studies compared solute transport rates from eviscerated (N = 6) and sham-operated rabbits (N = 5) with application of circumferential abdominal compression to control intraperitoneal pressure and presumably maximize dialysate-peritoneum contact. Series 3 studies compared solute transport rates from sham-operated rabbits (N = 4) with and without applied circumferential abdominal compression. Transperitoneal solute exchange of creatinine and FITC-labeled neutral dextran (15 to 40 A) was equally assessed by both the dialysate to plasma concentration ratio at the end of the exchange and the diffusive permeability-area product of the peritoneum. Evisceration reduced creatinine (P less than 0.001) and dextran (15 to 30 A, P less than 0.05) transport to approximately one quarter that of controls in series 1 rabbits. When circumferential abdominal compression was applied in series 2 rabbits, however, evisceration had no effect on peritoneal solute transport rates. Moreover, circumferential abdominal compression per se had no effect on solute exchange in series 3 experiments. These findings demonstrate that the influence of evisceration on peritoneal solute transport depends on the experimental conditions. These observations further demonstrate that visceral peritoneum is not essential for solute transport during peritoneal dialysis.

Liquid membrane phenomenon in vitamin E: studies on α-tocopherol

The liquid membrane phenomenon in vitamin E has been studied. Hydraulic permeability data have been obtained to demonstrate the existence of the liquid membranes in series with a supporting membrane generated by α-tocopherol and also by the lecithin-cholesterol-α-tocopherol mixtures. Data on the transport of oestrogen, progesterone, cystine, methionine, creatinine and sodium, potassium and calcium ions in the presence of the liquid membrane generated by the lecithin-cholesterol-α-tocopherol mixture have been obtained and discussed in the light of the various syndromes caused by vitamin E deficiency. The data indicate that modification in the permeability of the various relevant permeants in the presence of liquid membranes is likely to play a significant role in causing and prevention of the various syndromes due to the deficiency of vitamin E.

Peritoneal Transport Characteristics of Water, Low-Molecular Weight Solutes and Proteins during Long Term Continuous Ambulatory Peritoneal Dialysis

Peritoneal transport of water, low-molecular-weight solutes and proteins was studied on 75 occasions in 38 CAPD patients. Maximal ultrafiltration capacity decreased with time on CAPD, while there was an increase in the number of hypertonic bags used and the peritoneal absorption of glucose. A relationship was found between maximal ultrafiltration capacity and glucose kinetics. The duration of CAPD was longer in the patients with poor ultrafiltration, while they had a faster transport of glucose and creatinine, but not of proteins. In the group as a whole, no obvious changes were found in the mass transfer area coefficients of urea, creatinine and glucose, nor in the clearances of albumin and IgG. In the five patients with severe ultrafiltration loss, we found evidence of either decreased or increased peritoneal solute transport. Contrasting findings in transport of small solutes and proteins may reflect increased effective peritoneal surface area combined with decreased peritoneal permeability.

Evidence for bidirectional net movement of creatinine in the rat kidney.

Although the clearance of endogenous creatinine is used in many physiologic and metabolic studies in the rat as an index of glomerular filtration rate, there is no evidence that creatinine is a reliable test substance. Studies were therefore performed in anesthetized and conscious rats to determine the creatinine-to-inulin clearance ratio (CCr/CIn). In anesthetized animals the CCr/CIn ratio was 0.5 and in conscious rats it was 0.7 at normal basal plasma creatinine levels. After an increase in plasma creatinine to 1.9 mg/dl induced by the intravenous infusion of creatinine, the CCr/CIn ratio was 1.2. Accordingly, these data indicate that net creatinine transport across the renal tubule is bidirectional and that transport is influenced by the plasma creatinine level. At normal plasma levels creatinine is extensively reabsorbed along the nephron, whereas net secretion is associated with elevated plasma creatinine. The results demonstrate that creatinine is not a reliable marker of glomerular filtration rate in the rat.

The influence of trimethoprim, sulfamethoxazole, and creatinine on renal organic anion and cation transport in rat kidney tissue

The use of combined trimethoprim and sulfamethoxazole has been reported to increase serum creatinine concentrations in patients by inhibiting creatinine excretion. In confirmation, we found that trimethoprim given over 24 hr to rats augmented serum creatinine concentrations and decreased creatinine clearance relative to urea clearance. Previously, decreased urinary excretion has been hypothesized to occur secondarily to inhibited renal secretory transport of creatinine via the organic cation pathway, although there was no direct evidence to indicate that trimethoprim inhibits organic cation secretion. Such a mechanism is possible because other studies have shown that creatinine is secreted through both the organic anion and cation pathways. We followed organic anion ([ 3H]PAH) and organic cation ([ 14C]TEA) accumulation in incubating rat renal fragments in order to determine whether inhibition of organic cation accumulation by trimethoprim actually does occur. The present investigation shows that trimethoprim interferes with organic cation uptake in vitro but does not influence organic anion uptake. Sulfamethoxazole affected neither organic cation nor anion accumulation significantly. Trimethoprim decreased influx of [ 14C]TEA, not its efflux. Other metabolic processes such as QO 2, ammoniagenesis, and gluconeogenesis were not altered greatly by trimethoprim. Creatinine itself decreased organic anion and cation transport through competitive inhibition. Added to the findings that trimethoprim elevates serum creatinine in man without changing glomerular filtration rate, our results strengthen the hypothesis that trimethoprim can decrease serum creatinine excretion through the inhibition of creatinine secretion via the organic cation transport route.

Creatine and creatinine transport in old and young human red blood cells

The time course of creatine influx or efflux as measured in populations of red cells or red cell ghosts with normal age distribution does not follow simple two-compartment kinetics. This suggests that the contributions of individual cells to transport as measured in the populations as a whole are not uniform. In agreement with this inference, fractionation of red cell populations with respect to cell age shows that transport in young cells is considerably faster than in old cells. The dependence of creatine transport on creatine concentration in the medium follows an equation that can be interpreted to represent a super-imposition of a saturable component (apparent K m = 0.02 mM) and another component that cannot be saturated up to a creatine concentration of 5.0 mM. In contrast to the non-saturable component, the saturable component depends on the energy metabolism of the cell and can be inhibited by β-guanidinopropionic acid and the proteolytic enzyme pronase. This latter finding suggests that the saturable component represents active transport that is mediated by a transport protein. The non-saturable component is little, if at all, dependent on cell age while the saturable component is higher in young cells than in old cells. Phloretin inhibits both components of creatine flux, but the maximal inhibition that can be achieved at high concentration is only 70–80%. Under the experimental conditions used for the study of creatine transport, creatinine equilibration between cells and medium follows the kinetics expected for a steady-state two-compartment system. Creatinine flux is proportional to creatine concentration over the concentration range studied (up to 5 mM). It cannot be inhibited by β-guanidinopropionic acid or pronase.

In vitro and Clinical Evaluation on Creatinine Transport Dynamics in Blood

In vitro and Clinical Evaluation on Creatinine Transport Dynamics in Blood

Mechanism of the diuretic action of chloracizine

Chloracizine has a marked diuretic action and increases sodium excretion in rats although not by any direct action on the kidney. This effect is accompanied by an increase in the volume of intravascular fluid, a decrease in the total plasma protein concentration, and a decrease in the hematocrit index. A study of the endogenous creatinine clearance and transport of osmotically free water shows that the mechanism of the diuretic action of chloracizine is linked chiefly with an increase in the level of glomerular filtration and decrease in the relative proximal reabsorption.

Pressure-dependent PAH and creatinine transport from the brain ventricles.

The brain ventricular system of the adult dog was perfused with an artificial cerebrospinal fluid (CSF) containing inulin, creatinine and radioactively labeled p-aminohippuric acid (PAH) and mannitol. Inflow and outflow rates and concentrations of test molecules were measured at different intraventricular pressures, allowing calculation of their steady-state rates of removal from the ventricles. Clearance of inulin, a measure of CSF bulk absorption varied nearly with intraventricular pressure (- 15 to +12 cm H2O relative to the external auditory meatus). The efflux coefficient (Ko; representing clearance of a molecule by means other than bulk absorption) for mannitol was independent of intraventricular pressure. Ko's for PAH and creatinine were pressure dependent. PAH and creatinine efflux may be related to the amount of fourth ventricular choroid plexus surface exposed to the perfusion fluid. Ko's for creatinine and PAH (46 plus or minus 4 mul/min; 34 plus or minus 4mul/min, respectively) were significantly greater than mannitol (16 plus or minus 8 mul/min) at comparable intraventricular pressures, suggesting that both creatinine and PAH leave the CSF by an active process in addition to passive diffusion.

Permeability of synthetic polypeptide membranes. I. Poly‐D,L‐leucine‐co‐D,L‐methionine

AbstractD,L‐Leucine‐NCA and D,L‐methionine‐NCA were copolymerized in varying mole fractions by using primary base initiation. The methionine segments were oxidized to both sulfoxide and sulfone functions by using peroxide oxidation. The compositions of the resulting polymers were established with the aid of 60 MHz NMR. The transport properties of aqueous solutes through membranes formed from these polymers were studied by means of a diffusive dialysis measurement. The transport of NaCl, urea, creatinine, uric acid, and bacitracin were found to be strongly dependent on the degree of hydration of the polymers. The relative rates of transport of these solutes were affected by interaction with the polymers, when the degree of hydration was not excessive. The degree of hydration was a function of the extent of methionine oxidation.

THE TRANSPORT OF UREA, CREATININE AND CERTAIN MONOSACCHARIDES BETWEEN BLOOD AND FLUID PERFUSING THE CEREBRAL VENTRICULAR SYSTEM OF RABBITS.

THE TRANSPORT OF UREA, CREATININE AND CERTAIN MONOSACCHARIDES BETWEEN BLOOD AND FLUID PERFUSING THE CEREBRAL VENTRICULAR SYSTEM OF RABBITS.

Rubidium and creatinine transport across isolated mesentery

The movement of Rb 86 cations across isolated rabbit mesentery displays the kinetic pattern associated with passive diffusion. The permeability constant can be increased by the application of several drugs. Histamine markedly stimulates the movement of rubidium ions, while epinephrine and acetylcholine are much less effective. By measuring the contemporaneous transfer of the Rb 86 cation and of un-ionized creatinine, an attempt was made to expose the nature of the permeability barrier. A 10° rise in temperature produced a relatively greater elevation in creatinine permeability, while 5-HT was relatively more effective in enhancing the permeability to rubidium. The differential effects of these two environmental stimuli on the trans-mesenteric movement of two tracer substances indicate that these two stimuli must affect different parts of the transport process.

Creatinine transport between baby and mother at term

Creatinine transport between baby and mother at term