Some observations on the determination of extracellular fluid volume of jejunal tissue using [3H]inulin and [14C]inulin.
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Animals↗
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Practical approach for determining glomerular filtration rate by single-injection inulin clearance.
We compared the glomerular filtration rate as measured by a single-injection inulin clearance with that measured by a standard isotope method with 99mTc-labeled diethylenetriaminopentaacetic acid in 21 subjects with glomerular filtration rates greater than 35 mL/min. After a bolus injection of 5 g of inulin, blood samples were taken 20, 45, 90, 120, 145, 180, and 240 min afterwards. Inulin was measured by optimized chemical or enzymatic methods of high analytical sensitivity to determine inulin at low concentrations. We used the one-compartment model and inulin concentrations measured at two sampling times to calculate the glomerular filtration rate from the data of the disappearance curve of inulin. Inulin concentrations at 20 and 240 min after injection of the inulin bolus were suited to estimate glomerular filtration rate by this procedure, resulting in values (y) comparable with those obtained by isotope technique (x). The relationship to the isotope technique was characterized by the equation y = +4.80 mL/min + 0.92x (r = 0.97). The single-injection inulin clearance determination can detect a decrease of glomerular filtration rate at the beginning of kidney damage, given that our study included subjects with glomerular filtration rates greater than 35 mL/min. We conclude that the glomerular filtration rate can be determined by analyzing only two blood samples after a bolus injection of inulin.
Adult↗
[A modified microanthrone method for the determination of inulin on nanogram scale].
The establishment of a method of determining minute amount of inulin on nanogram scale is essential for applying micropuncture technique to kidney research. In this experiment, we modified a classical microanthrone method which was used by Dirks et al. to determine inulin contained in tubular fluid. A spectrophotometer was installed with a special microcuvette to suit the colorimetry of 10 microliters solution. Linear relation between inulin concentration and absorption was observed in the range of inulin concentration from 2 to 32 nl per 10 microliters anthrone reagent. The accuracy of this microanthrone method was evaluated with inulin recovery test, the mean recovery rate being 101.2 +/- 3.5%. Since tubular fluid did not interfere with the determination of inulin, the tubular fluid which contained inulin could be added directly to anthrone reagent in actual practice. The mean single nephron glomerular filtration rate measured with this modified microanthrone method in 21 rats was 34.9 +/- 1.8 nl/min, which coincided well with the values reported in literature. The results indicate that the measurement of inulin with the above-mentioned microanthrone method is reliable and suitable for the micropuncture study.
Animals↗
Uptake of inulin by cells in rat brain cortex.
Light and electron microscope autoradiography indicated that 3H-labelled inulin was taken up by neurons and glia cells of rat brain cortex in vitro. The mechanism, by which inulin passed the cell membranes, was studied by comparing the transport of inulin (molecular weight 5000) with the transport of dextran (molecular weight 75000). The half-time for the cellular in- and efflux for the two molecules was the same although their diffusion coefficients differed by a factor of 4-5. The transport mechanism was therefore interpreted as bulk transport, and vesicular transport is suggested. Efflux of inulin from brain cortex exposed to inulin in vivo indicated that cellular uptake of inulin also occurred in vivo.
Animals↗
Preparation of functionalized derivatives of inulin: conjugation of erythrocytes for hemagglutination and plaque-forming cell assays.
A method is described for preparing derivatives of alkali-stable polysaccharides for coupling to immunogen carriers or to sheep red blood cells (SRBC) for use in hemagglutination (HA) and plaque-forming cell (PFC) assays. Inulin, a beta (2 leads to 1)-linked polyfructosan was partially derivatized with carboxyl, aminoethyl or (p-aminophenyl)butyryl groups; the latter derivative was coupled to SRBC following diazotization. Optimal conditions for the sensitization of SRBC with inulin were given. The immunological reactivity of the inulin molecule was unaffected by the derivatization reactions, and high, reproducible anti-inulin HA titers for inulin-binding myeloma proteins were found using these specifically sensitized SRBC. The sensitized SRBC were stable for assays for over 2 weeks. Problems with spontaneous agglutination or distortion of sensitized SRBC, normally seen in other procedures, e.g., methods using stearoyl-inulin, were not encountered.
Animals↗
Reassessment of the single intravenous injection method with inulin for measurement of the glomerular filtration rate in man.
1. Factors influencing the total body and renal clearances of inulin were investigated in a total of 37 healthy adult volunteers and 10 patients with stable chronic renal failure after the single intravenous injection of a dose of 70 mg/kg given over 5 min. 2. The elimination of inulin was highly concentration-dependent, and in healthy volunteers the renal clearance fell from 103.7 +/- 14.4 ml min-1 1.73 m-2 during the first hour after administration to 49.1 +/- 20.9 ml min-1 1.73 m-2 over the period 6-8 h. In the patients with renal failure the renal clearance fell correspondingly from 39.7 +/- 16.5 to 26.6 +/- 8.6 ml min-1 1.73 m-2. There were no changes in the simultaneously measured clearances of creatinine. 3. The values obtained for the total body clearance of inulin after a single injection depend critically on dose, the number and timing of blood samples, the choice of pharmacokinetic model, the number of data points chosen for estimation of the slope of the terminal elimination phase for analysis by the methods of residuals, and the weighting used for curve fitting by non-linear regression analysis. 4. With standardized conditions of sampling from 0 to 2 h and weighted non-linear regression analysis of the plasma concentration-time data, the total body and renal clearances of inulin were almost identical in subjects with normal renal function at 105.2 +/- 10.2 and 102.9 +/- 13.0 ml min-1 1.73 m-2. In the patients with chronic renal failure sampling was continued for 3 h and the corresponding clearances were 40.4 +/- 15.3 and 38.9 +/- 15.7 ml min-1 1.73 m-2. 5. The 0-2 h total body and renal clearances of inulin were measured by the single injection method and the renal clearance was measured by the standard constant infusion method on different occasions in 10 healthy volunteers. The respective clearances were similar at 101.4 +/- 6.6, 94.9 +/- 11.9 and 88.4 +/- 12.1 ml min-1 1.73 m-2. 6. The reproducibility of the single injection and constant infusion methods was compared by measuring the inulin clearance with both techniques on three occasions in separate groups of eight and nine healthy volunteers. The mean coefficient of variation for the total body clearance with the single injection method was only 3.9% compared with 9.5% for the renal clearance determined the same way and 12.0% for the renal clearance during constant infusion.(ABSTRACT TRUNCATED AT 400 WORDS)
Adult↗
Distribution of inulin, sucrose and mannitol in rat brain cortex slices following in vivo or in vitro equilibration.
1. The distribution spaces of inulin, sucrose and mannitol in rat brain cortex slices were determined in tracer experiments. Tracer equilibration times of 5 hr were used with combined ventriculo-cisternal perfusion and I.V. infusion of tracers. After 5 hr of equilibration the distribution volumes (expressed as mul./100 mg wet wt.) obtained using the perfusion fluid as reference and after correction of tracer amount in residual blood were obtained. Information on cellular uptake was obtained by examining a slow component of wash-out curves from brain slices after in vivo equilibration. Distribution spaces were corrected for intracellular penetration to obtain the extracellular volumes of distribution. Inulin was found to equilibrate with 13.3 mul. extracellular tissue water per 100 mg initial wet weight, sucrose with 16.6 mul. and mannitol with 19.5 mul.2. Marker spaces in rat brain cortex slices were also analysed by compartmental analysis of efflux of tracer inulin, sucrose and mannitol following in vitro incubation in a balanced medium for 60 min. Following in vitro equilibration, inulin was found to equilibrate with 22.4 mul. extracellular tissue water per 100 mg of final wet weight, sucrose to equilibrate with 31.7 mul. extracellular tissue water and mannitol with 42.3 mul.3. Inulin space in vitro when allowance is made for swelling produced during incubation of the slice was similar to the chemically delineated extracellular distribution volume in vivo. Sucrose and mannitol spaces in vitro, however, did not accord with in vivo determinations, most likely due to access of markers to areas of cell damage in the slice arisen during incubation.4. Comparison of fluid spaces delineated by inulin in slices of rat cerebral cortex following in vivo and in vitro equilibration indicated that swelling produced during incubation in vitro mainly occurred in the extracellular space. Swollen glial cells may account for the small, but significant intracellular swelling in incubated slices.
Animals↗
Discrepancy between circadian rhythms of inulin and creatinine clearance.
To elucidate the disparity between circadian rhythmicity of inulin and creatinine clearance, we simultaneously measured inulin and creatinine clearances every 3 hours during 1 day in 14 normal subjects and in 8 patients with nephrotic syndrome. All patients and normal subjects had a circadian rhythm for inulin clearance with a maximum during daytime and a relative amplitude of 21% +/- 2%. For creatinine clearance a rhythm was either absent or reduced in relative amplitude (p less than 0.01). In all subjects the rate of tubular creatinine secretion was higher at minimum of inulin clearance (night) than at maximum (day). The fractional clearance (relative to inulin) of creatinine was also higher during the night: normal subjects, 1.28 +/- 0.02 versus 1.10 +/- 0.02; patients, 1.78 +/- 0.08 versus 1.45 +/- 0.05 (p less than 0.005). This demonstrates the inaccuracy of creatinine clearance as a measure of glomerular filtration rate (GFR). By subsequent blocking of the tubular secretion of creatinine with cimetidine in four normal subjects, creatinine clearance became similar to inulin clearance during day and night. This confirms that high tubular secretion of creatinine during the night counteracts the normal rhythmicity of glomerular filtration of creatinine. As a result, plasma creatinine concentration is nearly constant during a 24-hour period. In conclusion, tubular creatinine secretion has a circadian rhythm with a phase opposite to the rhythm of GFR, thus blunting or causing absence of a circadian rhythm for creatinine clearance.
Adult↗
Humoral immune responses in mice using gamma inulin preparations as adjuvants for hepatitis B vaccines.
There is an urgent need for new, powerful adjuvants suitable for use with sub-unit and peptide vaccines in humans. We have measured the humoral immune response in BALB/c mice to vaccine formulations using recombinant HBsAg antigens, and gamma inulin and alum adjuvants. Using Merck, Sharpe & Dohme (MSD) HBsAg at 10 micrograms/mL, high levels of anti-HBs were generated and geometric mean S/N ratios of 88, 133 and 107 were obtained for alum absorbed vaccine, gamma inulin, and a mixture of the two adjuvants, respectively. A dilution series produced ED50 values of 0.08, 0.15 and 0.22 micrograms/mL respectively. In a second series of experiments comparing alum and algamulin (a complex of gamma inulin and alum), MSD HBsAg induced anti-HBs levels of 81 and 52, and ED50 values of 0.3 and 0.4 when used in conjunction with alum and algamulin, respectively. SKF HBsAg induced anti-HBs levels of 126 and 111 with alum and algamulin, and ED50 values of 0.11 and 0.075. The class, subclass and level of antibody produced in mice boosted with a second dose of vaccine at 21 days was also examined. Both alum and gamma inulin induced higher levels of total antibody, IgG1 and minor IgG subclasses than algamulin, or HBsAg alone. Overall, gamma inulin appears to be an equivalent adjuvant to alum, although their mechanisms of action are different. Mixtures or complexes of the two adjuvants appear to be less effective in inducing humoral immune responses in mice than either alone.
Adjuvants, Immunologic↗
Tissue uptake of insulin and inulin in red and white skeletal muscle in vivo.
By employing a tissue uptake technique, the kinetics of the plasma-interstitial equilibration of radiolabeled insulin, inulin, and albumin were followed in four muscles of differing capillarity in anesthetized rats. The soleus muscle (SOL), and the red portion of the gastrocnemius muscle (RG), as well as the extensor digitorum longus muscle (EDL) and the white portion of the gastrocnemius muscle (WG) were investigated. After constant intravenous tracer infusions and repeated plasma sampling under euglycemic clamp conditions, animals were killed at varying time intervals and the muscles mentioned above were dissected out. The radioactivity of tracer per gram of tissue in each muscle divided by the plasma activity of tracer per milliliter of plasma, i.e., "the plasma equivalent space" of tracer, thus could be followed as a function of time. From this function the permeability-surface area (PS) of inulin as well as the distribution volumes at time 0 (V0) of inulin and insulin and their equilibrium distribution volumes (VE) were assessed. The PS for inulin (in ml.min-1.100 g muscle-1) was 0.52 +/- 0.10 (mean +/- SE) in WG, increasing with more red fibers to 1.37 +/- 0.18 in SOL. Also the inulin interstitial distribution volume (at blood-tissue tracer equilibrium; VE) increased in this order (in ml/100 g) from 7.30 +/- 0.91 in WG to 12.93 +/- 0.89 in SOL. The V0 for insulin was found to be approximately fivefold larger than the plasma volume in each muscle sample, indicating a high degree of binding of insulin to structures within the vascular compartment, conceivably to the vascular endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Variations in serum complement following inulin infusion in man.
Complement levels were determined in 12 normal human volunteers while receiving intravenous infusions of inulin for determination of standard inulin clearances. Significant decreases in beta IC globulin and total hemolytic complement activity were observed when inulin was infused, but not following infusion of saline as a control. These effects were noted only when steady-state inulin levels were greater than 26 mg%, suggesting a dose-dependent response. No evidence of increased coagulation was noted as measured by fibrinogen and fibrin degradation products. Since C4 levels remained largely unchanged following inulin infusion, it was concluded that the results most likely occurred through activation of the alternate complement pathway.
Adult↗
Inulin, Containing Frutco-Oligosaccharides, and Generalized Anxiety Disorder 7-Item Scale Scores in College Students.
This study was conducted to determine the effects of fructo-oligosaccharide (FOS) inulin on anxiety symptoms in college students. Forty million adults in the United States suffer from anxiety. Previous studies have viewed gut microbiota and its potential link to anxiety in both humans and mice. However, no previous studies focused on the effect of FOS inulin on college students. Fourteen subjects received 4.9 g per day of FOS inulin as the treatment (TX) or no supplement as the control (CON) for 28 days. Both the TX and CON groups were given the Generalized Anxiety Disorder 7-Item Scale (GAD-7) on days 1 and 28. Both groups were also given a 3-day food log at the beginning of the experiment and otherwise maintained their regular diet. Results showed a statistically significant decrease in median GAD-7 scores in both groups (P = .017, r = .637 and P = .042, r = .587 for the TX and CON groups, respectively). However, when comparing the GAD-7 scores between groups, no statistically significant results were found. FOS inulin supplementation did not alleviate anxiety symptoms in college students participating in this study.
Adolescent↗
Passage of inulin and p-aminohippuric acid through artificial membranes: implications for measurement of renal function.
Diffusion of inulin and p-aminohippuric acid (PAH) in combined aqueous solution through artificial membranes was measured at room temperature and atmospheric pressure. The membranes had pore diameters of 26, 50, 100, 200, 250, 350, 510 or 990 A. The diffusion of PAH was only restricted with a pore size of 26 A, but inulin diffusion was restricted at 100 A. When diffusion of both solutes was unrestricted (pore diameter greater than or equal to 200 A), PAH diffused four times faster than inulin, and in restricted situations this ratio was even greater. The results of these diffusion studies allow the major and minor molecular dimensions of the solutes to be estimated. Filtration of the two solutes was studied in slowly flowing situations and also with increased temperature and pressure. Pore sizes required for unrestricted filtration were the same as for unrestricted diffusion but the passage ratio was reduced from 4 to 2. These results suggest strongly that two conditions are necessary if the glomerular filtration rate (GFR) of inulin is to equal the true GFR: membrane pore size must be at least 200 A and passage through the membranes must be by bulk transport.
Aminohippuric Acids↗
Peritoneal clearance of creatinine and inulin during dialysis in dogs: effect of splanchnic vasodilators.
The peritoneal clearance of creatinine and inulin during isotonic peritoneal dialysis was studied in dogs before and after the administration of two vasodilators: isoproterenol and glucagon. One-liter exchanges with 15-min dwell times were used. Blood flow in the superior mesenteric artery was recorded with an electromagnetic flow probe and used as an index for total splanchnic flow. Intravenous isoproterenol (2.4 microgram/min) increased blood flow by 88%, but did not alter peritoneal clearance. When isoproterenol was given i.p. (0.5 microgram/ml dialysis fluid), blood flow increased by 81%, and inulin clearance rose by 26.8% (2.06 +/- 0.18 to 2.61 +/- 0.23 ml/min; P less than 0.05). Creatinine clearance increased by 17.5%, from 10.94 +/- 0.32 to 12.85 +/- 0.34 ml/min (P less than 0.05). When blood flow was returned to control levels with a clamp, clearances also returned to control levels. Glucagon given i.p. (1.0 microgram/ml) had no effect on any measured variable. Glucagon given i.v. at 10 microgram/min caused blood flow to rise by 81% and inulin clearance to rise by 25% from 1.88 +/- 0.16 to 2.35 +/- 0.19 ml/min (P less than 0.05). Cp, inulin clearance remained at control levels. Vasodilators seem to exercise two effects in augmenting clearance of small and middle-sized molecules: a direct permeability effect and a blood-flow related effect, possibly in increasing the surface area available for exchange and/or increasing permeability of the capillary endothelium.
Animals↗
Sequence variation among heavy chains from inulin-binding myeloma proteins.
The entire sequences of the variable region of four heavy chains from BALB/c inulin-binding myeloma proteins have been determined. Among the four proteins there are six amino acid differences, all of which occur in the framework portion of the variable region. All of the six amino acid substitutions can be explained by single base mutations at the DNA level. The pattern of diversity in these proteins is compared to a previously reported group of heavy chains from phosphorylcholine-binding myeloma proteins. Unlike the phosphorylcholine-binding proteins, which (with the exception of two that are identical) have size and sequence differences in their complementarity regions, the inulin-binding heavy chains all have identical complementarity regions with H3 being extremely short. The pattern of variation observed in the anti-inulin heavy chains appears to be most easily explained by a somatic mutation mechanism. However, because none of the substitutions occur in complementarity-determining regions, they presumably would have no selective advantage and would not alter binding specificity. These proteins have further been shown to have crossreacting antigenic determinants (idiotypes). Five of the six sequence differences observed occur at positions that are internal in the molecule and thus presumably would not account for the idiotypic differences. These results suggest that most of the observed idiotypic crossreactivities will be due to differences in the light chains of the anti-inulin proteins.
Amino Acid Sequence↗
Transcapillary exchange of 14C-inulin by free diffusion in channels of fused vesicles.
Capillary permeability for the extracellular, hydrophilic indicator 14C-inulin, was determined in the autoperfused cat gastrocnemius muscle by bolus injection, venous sampling expts. The capillary diffusion capacity, CDC (the permeability-surface are product, PS), was 0.84 ml/100 g-min, and capillary extraction, E, was 0.307 at a plasma flow of 4.0 ml/100 g-min as average values of 7 expts. Results were compared with 51Cr-EDTA and 57Co-B12 data of previous studies. The findings imply that 14C-inulin is not subject to restricted diffusion across the continuous capillary membranes of skeletal muscle as compared to 51Cr-EDTA as well as 57Co-B12. These hydrophilic indicators pass the capillary barrier at rates proportional to their respective free diffusion coefficients in water. The Pappenheimer equivalent pore radius estimate of 30 A (or slit width of 37 A) and the Karnovsky 40 A interendothelial slit width are inconsistent with the present data which imply a much larger pore size. The transendothelial channel system of fused vesicles is a possible morphological equivalent for the present findings which support the general theory that capillaries of continuous type exhibit similar permeation characteristics regardless of the tissue in which they are located. By kinetic black-box analysis the extravascular distribution volume for 14C-inulin in skeletal muscle was found to be 13.0 ml/100 g. The data indicate that 51Cr-EDTA, which has about the same molecular radius as sucrose, and 14C-inulin have identical extravascular volumes of distribution and that both molecules presumably enter the sarcoplasmic reticulum.
Animals↗
Distribution of subcutaneously administered inulin between blood and peripheral lymph in the rabbit.
In experiments on rabbit peripheral lymph, the contribution of the blood and lymphatic system to the whole-body distribution of inulin after subcutaneous administration has been investigated and the effects of hyaluronidase and of thermal stimulus at the administration site examined. Inulin concentrations in lymph exceeded plasma concentrations by more than 100-fold. At the end of the experiment (90 min) the amount of drug in the total lymph collected was about one-seventh the amount found in urine. The blood system, as a result of higher circulation at the administration site distributes inulin from the subcutis more rapidly than does lymph. Hyaluronidase did not influence inulin concentrations in blood and lymph but thermal stimulus significantly decreased both concentration and total distribution. The decrease resulted from a developed oedema and vasoconstriction in the skin and subcutis of the cannulated extremity.
Animals↗
Early postglomerular plasma concentrations of chloride, sodium, and inulin in the rat kidney.
Sodium, chloride, and inulin concentrations were measured in plasma collected from the terminal portions of long efferent vessels at the subcapsular surface of the rat kidney. Sodium concentration equaled and the concentrations of chloride and inulin were less than those in peripheral plasma. During benzolamide infusion, chloride concentration equaled while inulin concentration remained less than in peripheral plasma. In free-flow micropuncture samples collected randomly during control conditions, chloride concentration rose rapidly in the early proximal tubule and then remained elevated and constant throughout the remainder of the proximal tubule accessible to micropuncture. These experiments indicate that normally tubular reabsorbate low in chloride and inulin is added to the blood traversing the early postglomerular vessels before reaching the kidney surface. Bases on the analyses of proximal tubular fluid, this type of reabsorbate appears available only from the early proximal tubular segment. We conclude that a close functional relationship exists between the first segment of the proximal tubule and the early postglomerular blood supply characteristic of the superficial cortical nephron.
Animals↗