Intestinal permeability after Mediterranean diet and low-fat diet in non-alcoholic fatty liver disease

BACKGROUND

In non-alcoholic fatty liver disease (NAFLD), a high-fat or high-fructose diet increases intestinal permeability and promotes derangement of the gut-liver axis. We hypothesize that, diet could be able to modulate intestinal permeability in patients with NAFLD.

AIM

To detect diet-induced modification of intestinal permeability in patients with NAFLD undergoing a Mediterranean diet or a low-fat diet.

METHODS

The current study was a dietary intervention for non-diabetic, patients with biopsy-verified NAFLD and increased transaminases. A crossover design was employed: participants underwent 16 weeks of Mediterranean diet, 16 wk of free wash-out, and 16 weeks of low-fat diet. Both diets were hypocaloric and no consumption of supplements was allowed. All patients were followed bimonthly by a dietitian. Evaluations of clinical and metabolic parameters were completed at baseline and at the end of each dietary period. Intestinal permeability was assessed by chromium-51 ethylene diamine tetraacetate excretion testing (51Cr-EDTA).

RESULTS

Twenty Caucasian patients, 90% male, median age 43 years, body mass index (BMI) 30.9, with biopsy-verified NAFLD were enrolled. At the end of 16 weeks of a Mediterranean diet, a significant reduction in mean body weight (-5.3 ± 4.1 kg, P = 0.003), mean waist circumference (-7.9 ± 4.9 cm, P = 0.001), and mean transaminase levels [alanine aminotransferase (ALT) -28.3 ± 11.9 IU/L, P = 0.0001; aspartate aminotransferase (AST) -6.4 ± 56.3 IU/L, P = 0.01] were observed. These benefits were maintained after 16 wk of wash-out and also after 16 wk of low-fat diet, without further improvements. Fourteen of the 20 patients had intestinal permeability alteration at baseline (mean percentage retention of 51Cr-EDTA = 5.4%), but no significant changes in intestinal permeability were observed at the end of the 16 wk of the Mediterranean diet or 16 wk of the low-fat diet.

CONCLUSION

Mediterranean diet is an effective strategy for treating overweight, visceral obesity and serum transaminase in patients with NAFLD. If the Mediterranean diet can improve intestinal permeability in patients with NAFLD, it deserves further investigation.

Estimation of glomerular filtration rate in patients with systemic lupus erythematosus

The objective of this study was to compare the limit of agreement of creatinine clearance (CrCl) estimated by different equations with the CrCl measured by 24-hour urine collection in Hong Kong Chinese patients with systemic lupus erythematosus (SLE). Forty-three SLE patients with mild to moderate renal impairment (serum creatinine concentration 80 mol/L to 300 mol/L for females; and 106 mol/L to 300 mol/L for males) and not requiring renal replacement therapy were assessed. The estimated clearances were calculated by the Cockcroft-Gault (CG) equation, the Modification of Diet in Renal Disease (MDRD) study equation and the abbreviated MDRD (aMDRD) study equation. The estimated clearances were compared against the measured CrCl by 24- hour urine collection for their limit of agreement. Forty-three patients with mean (SD) age of 41.6 (8.4) years were assessed. As compared to the measured CrCl in patients with SLE, the clearances by CG equation, MDRD and aMDRD equations predicted a mean difference of 0.8% (95% confidence interval, 43.9-42.3%); 8.6% (95% CI, 24.3-7.2%) and 4.7% (95% CI, 21.4-12%), respectively. There is a tendency for the MDRD and aMDRD study equations to underestimate CrCl. The MDRD and aMDRD study equations have better predictive value than the CG equation.

[Monitoring renal function in patients treated with cytostatics]

INTRODUCTION

Some cytostatics, used in the treatment of cancer, are excreted by the kidneys and may be nephrotoxic. The glomerular filtration rate (GFR) represents a method for reliable assessement of the 51Cr-EDTA plasma clearance before and during treatment with nephrotoxic drugs. The aim of this retrospective study was to evaluate whether this method could be replaced by a more simplified GFR estimate calculated from the creatinine plasma concentration.

MATERIALS AND METHODS

We included all patients who had had at least four GFR measurements in 2005 as part of their nephrotoxic cytostatic treatment. The estimated GFR (eGFR) was calculated from sex, age and weight, according to the Cockcroft formula.

RESULTS

Forty-eight patients with a mean age of 47 years were included. 51Cr-EDTA plasma clearance and eGFR showed a poor correlation (r(2) = 0,678). On average, GFR decreased from 95 ml/min to 80 ml/min from the first to the fourth measurement, whereas plasma concentration of creatinine and eGFR remained unchanged. In 13 patients (27%), the treatment dose was reduced due to a fall in GFR. Seven of these 13 patients would have continued their treatment unchanged, if the clinical decision had been based on eGFR.

CONCLUSION

Neither creatinine plasma concentration nor estimated GFR ad modum Cockcroft can be recommended for measurement of GFR in patients treated with nephrotoxic cytostatics.

Comparison between slope–intercept and slope-only techniques for measuring glomerular filtration rate: Use of two independent markers and an independent arbiter

PURPOSE

Exclusive use of the half-time of clearance of a filtration marker in the bolus injection, single compartment technique for measuring glomerular filtration rate (GFR) is a convenient approach that gives GFR (GFR(SO)) already scaled for extracellular fluid volume (ECV). It has been criticized as less accurate than the conventional, slope-intercept technique (GFR(SI)). The aim of the study was to compare the respective levels of agreement of GFR(SI) and GFR(SO) with GFR based on plasma creatinine (eGFR) used as an independent arbiter.

METHODS

GFR was measured with both 51Cr-EDTA and iohexol, simultaneously injected into opposite arms. Plasma obtained bilaterally 20, 40, 60, 120, 180 and 240 min after injection was assayed for marker injected contra-laterally, 51Cr-EDTA by well-counting and iohexol by X-ray fluorescence. ECV and GFR, scaled to body surface area (BSA), were formally measured from six samples and GFR(SI) (scaled to BSA) and GFR(SO) from the last three.

RESULTS

Disagreement between GFR(SO) measured with 51Cr-EDTA and eGFR was not significantly higher than the corresponding disagreement between eGFR and GFR(SI). Disagreement between GFR(SO) measured with iohexol and eGFR was significantly higher than between eGFR and GFR(SI). GFR(SI) and GFR(SO) correlated more closely when measured with 51Cr-EDTA than with iohexol. Individual differences between GFR(SI) and GFR(SO) using one marker correlated significantly with ECV measured with the other.

CONCLUSIONS

GFR(SO) is critically dependent on the accuracy of half-time measurement and, measured with iohexol, appeared less reliable than GFR(SI). GFR(SI) and GFR(SO) measured with 51Cr-EDTA, however, have similar levels of reliability.

Decline in 51Cr-labelled EDTA measured glomerular filtration rate following lung transplantation

BACKGROUND

The nephrotoxity of calcineurin inhibitors in lung-transplanted patients is well described, but previous studies have estimated rather than directly measured glomerular filtration rate (GFR). This study describes the decline of measured GFR in a large cohort of lung-transplanted patients from a national centre, and the correlation between measured and calculated GFR.

METHODS

All lung-transplanted patients 1992-2004 (n = 390) were included in a longitudinal analysis. Seven patients were excluded due to retransplantation. Pre- and post-transplant parameters included (51)Cr-labelled EDTA clearance (mGFR) and the Cockcroft-Gault calculated clearance (cGFR). Trough cyclosporine levels (C0) and demographic and transplant information were also included in the analysis.

RESULTS

A total of 66959 C0 and serum creatinine and 1945 mGFR measurements pertaining to 383 patients were included in the analysis. Pre-transplant mGFR was significantly lower with respect to recipient age over 60 years; and patients with a referral diagnosis of pulmonary hypertension had a lower mGFR and higher baseline serum creatinine levels than patients with emphysematous disease (P < 0.05). There were linear correlations between log(10) mean interval serum creatinine and log(2) mGFR at all time points pre- and post-transplantation (P < 0.0001, Spearman correlation coefficient = -0.81) and between log(2) cGFR and log(2) mGFR (P < 0.0001, Spearman correlation coefficient = 0.81), however, the agreement between mGFR and cGFR was poor (-2.7 +/- 38.6 ml/min). A simplified repeated measure ANOVA model describing post-transplant GFR over time demonstrated a 54% decline in mGFR within the first 6 months post-transplant. Pre-transplant mGFR was an important determinant of 6 month post-transplantation mGFR. Increasing mean C0, body mass index and early acute renal failure were independent risk factors for a more rapid decline in post-transplant mGFR.

CONCLUSION

mGFR decreases dramatically during the first 6 months after lung-transplantation. Avoidance of high dose calcineurin inhibition may postpone the onset of post-transplant end-stage renal failure.

Intestinal paracellular permeability is not affected in chronic congestive heart failure

BACKGROUND

In chronic heart failure (CHF) it has been proposed that a dysfunction of the gastrointestinal barrier could lead to translocation of endotoxin into the systemic circulation. A secondary inflammatory reaction, observed as increased levels of cytokines, could negatively affect cardiac function. The aims of this paper were therefore to determine whether patients with CHF have a disturbed mucosal barrier and whether it was possible to detect endotoxin in venous blood.

METHODS

Nineteen stable patients with CHF (New York Heart Association II-III, EF<or=40% or EF>40% and earlier hospitalisation for heart failure) were investigated. Twenty healthy subjects (HS group) and 25 patients, who were admitted for bone marrow transplantation (BMT group), served as controls. Gastrointestinal permeability was assessed by a (51)Cr-EDTA absorption test.

RESULTS

Eleven patients with and eight without peripheral oedema were included. Median age was 76.5 years. Intestinal permeability was 1.82+/-1.96% in the CHF patients and 1.54+/-.59% and 1.9+/-.9% in HS and BMT groups, respectively (p=0.4 and p=0.7, CHF vs HS and BMT, respectively). No difference was found between patients with and without oedema and endotoxins were below the detection limit in all patients.

DISCUSSION

This study does not support the hypothesis that patients with CHF have a dysfunctional gastrointestinal barrier, at least as assessed by the (51)Cr-EDTA resorbtion test.

Susceptibility of glomerular filtration rate estimations to variations in creatinine methodology: a study in older patients

BACKGROUND

It is recommended that measurement of serum creatinine should be supplemented with a creatinine-based estimation of glomerular filtration rate (GFR). The influence of creatinine methodology on these estimates is not always appreciated. We have studied differences in creatinine methods and their influence on GFR estimation specifically in older people.

METHODS

In all, 46 older patients (mean age 80 y, range 69-92 y) with predominantly mild or moderate kidney disease were studied. Serum creatinine was measured using a rate Jaffe method and two different enzymatic methods. Isotope dilution mass spectrometry served as the reference creatinine method. GFR was estimated using both the Modification of Diet in Renal Disease (MDRD) and Cockcroft and Gault formulae: a 51Cr-EDTA GFR estimation served as the reference GFR method.

RESULTS

Both enzymatic methods produced creatinine results that were significantly different (P<0.001) from the reference method. The Jaffe method over- and underestimated creatinine at low and high concentrations, respectively. The most likely explanation for these differences relates to standardization of the assays. Irrespective of creatinine method, the Cockroft and Gault formula tended to underestimate GFR, and the MDRD formula to overestimate GFR. Use of the differing creatinine methods to estimate GFR produced predictable biases of the estimate, with mean GFR estimates varying by 14% across the creatinine methods.

CONCLUSION

Estimates of GFR depend critically upon the accuracy and precision of the creatinine measurement used in their calculation.

Bioaccumulation of 51Cr, 63Ni and 14C in Baltic Sea benthos

The Baltic Sea is a species-poor, semi-enclosed, brackish sea, whose sediments contain a wide range of contaminants, including sediment-associated metals and radionuclides. In this study, we have examined and compared bioaccumulation kinetics and assimilation efficiencies of sediment-associated (51)Cr, (63)Ni and (14)C in three key benthic invertebrates (the deposit-feeding Monoporeia affinis, the facultative deposit-feeding Macoma baltica, and the omnivorous Halicryptus spinulosus). Our results demonstrate that (i) all radionuclides were accumulated, (ii) the different radionuclides were accumulated to various extents, (iii) small changes in organic carbon concentration can influence the accumulation, and (iv) the degree of accumulation differed only slightly between species. These processes, together with sediment resuspension and bioturbation, may remobilise trace metals from the sediment to the water and to higher trophic levels, and therefore should be taken into account in exposure models and ERAs.

Short-term distribution of 134Cs in relation to 51Cr-EDTA after intravenous dose in goats

AIM

The aim of this study was to gather information about the short-term rate of caesium uptake (incorporation) in different animal tissues and explain them with known physiological mechanisms affecting ion distribution.

METHODS

Six goats were given an intravenous bolus containing (134)Cs as a tracer and (51)Cr-EDTA as an extracellular marker. After 30 min, the animals were killed and the activity concentration of radioactive isotopes in different tissues and fluid compartments were measured.

RESULTS

The highest relative activity concentration of (134)Cs was found in kidney cortex, with a tissue/plasma-ratio around 50. In urine, the ratio varied between 5 and 28. In the salivary gland, cardiac muscle and small intestine the ratio was around 11, 7 and 6, respectively. The contents of small intestine had an average activity concentration five times that of plasma. In skeletal muscle the terminal activity concentration was surprisingly low, with a tissue/plasma ratio mostly far less than unity. Even in connective tissue and cartilage the terminal activity concentration was generally higher than in skeletal muscle.

CONCLUSION

The rate of uptake of caesium varies widely from tissue to tissue. Many of these differences can be explained with differences in Na,K-ATPase activity. Also, perfusion and accessibility play a role in some tissues, like brain and possibly part of the skeletal muscles. The short-term distribution of caesium differs distinctly from the long-term distribution reported in literature.

An acute stressor enhances sensitivity to a chemical irritant and increases 51CrEDTA permeability of the colon in adult rats

We investigated the effect of prior acute stress on colonic permeability induced by a chemical irritant known to induce symptoms similar to inflammatory bowel disease in rodents. Adult male rats (n = 12) were stressed by a single session of ten unpredictable, uncontrollable foot shocks, and half were home cage controls (n = 12). Twenty-nine days later, half of each treatment group was exposed to 4% DSS (dextran sulphate sodium) solution in their drinking water for 48 hours while half received pure water over two periods separated by 17 days. After food deprivation overnight and light isoflurane anaesthesia the following morning, the animals were given a colonic infusion of 2000 nCi (nanocurie) 51CrEDTA (51Cr-labelled ethylenediaminetetraacetic acid) and then placed individually in metabolic cages for a six hours continuous urine collection. Radioactivity in urine was measured by a gamma counter and percentage recovery of 51CrEDTA calculated as an indicator of colonic mucosal permeability. Results concluded that pre-shocked animals exposed to DSS showed significantly higher mucosal permeability than the pre-shocked animals given water, and the non-shocked animals given either DSS or water. Pre-shock in combination with two exposures to a chemical irritant separated by 17 days had a pronounced effect on colonic permeability, indicating that stress should be considered a possible initiating or contributory factor to increased intestinal permeability related to a mucosal challenge.

51Cr-EDTA absorption blood test: an easy method for assessing small intestinal permeability in dogs

The 51Cr-EDTA test is a valuable clinical tool for screening intestinal diseases in dogs. The test is performed by calculating the percentage of recovery from urine of a PO-ingested dose of 51Cr-EDTA after 6 or 24 hours. Careful urine collection is a practical limitation of this test in dogs, and our goal was to develop a simpler test that measures 51Cr-EDTA in blood. A 51Cr-EDTA absorption test was simultaneously performed on urine and serum 43 times in healthy Beagle Dogs. Timed blood samples were withdrawn, and urine was collected during a 6-hour period. Percentages of the ingested dose were then calculated in urine and serum. The mean +/- standard deviation (range) percentage in urine after 6 hours was 14.07 +/- 8.72% (3.81-34.18%), whereas results in serum from samples taken at 2, 3, 4, 5, and 6 hours were 0.49 +/- 0.45% (0.02-2.13%), 0.75 +/- 0.52% (0.03-1.89%), 0.82 +/- 0.57% (0.13-2.21%), 0.70 +/- 0.53% (0.12-1.99%), and 0.47 +/- 0.44% (0.11-1.79%), respectively. The results for blood specimens showed good concordance with those for urine, especially for the samples taken at 4 hours (r = 0.89). Moreover, the correlation between urine and blood was better when the sum of the percentages of the recovered analyte from various blood samples was compared with urine. The correlation coefficient when summing 4 blood samples was excellent (r = 0.97) and remained excellent when summing only 2 blood samples taken at 3 and 5 hours (r = 0.95) or at 3 and 4 hours (r = 0.94). We conclude that a serum 51Cr-EDTA test determined by summing successive blood samples provides an easier means of estimating small intestinal permeability in dogs and gives results comparable to those of the 6-hour urine test.

Time to complete mixing for the measurement of glomerular filtration rate from single bolus plasma 51Cr-EDTA clearance

BACKGROUND AND METHOD

In the measurement of glomerular filtration rate from the plasma clearance of 51Cr ethylenediamine tetraacetic acid by using the slope-intercept method, the first sample is conventionally taken at 2 h, the time by which it is generally assumed that the clearance curve has reached a single exponential. We examined this assumption by comparing the slopes, alpha 12 and alpha 23, based, respectively, on samples at 2 and 3 h, and at 3 and 4 h.

RESULTS

In 421 patient studies in whom the first sample was taken between 110 and 130 min after injection, the mean ratio, alpha 12/alpha 23, was 1.101 (SEM 0.011) which is significantly higher than unity (P<<0.001). The relationship between alpha 12/alpha 23 and the slope, alpha 13 (which is a measure of filtration function already indexed for body size) based on all three samples was negative. By modelling the relationship between mixing time and alpha 13 it was shown that this relationship suggests delayed mixing of the indicator throughout its distribution volume and is inconsistent with irreversible binding of indicator to plasma protein. A significant positive association was observed between alpha 12/alpha 23 and age, but this is largely explained by a generally poorer filtration function in the older age group since low levels of alpha 13 theoretically predict a longer mixing time. In 188 patient studies in whom the first sample was taken more than 130 min after injection, the mean ratio, alpha 12/alpha 23, was 1.055 (SEM 0.017) which is still significantly higher than unity (P<<0.005) but significantly less than the ratio based on studies in which the first sample was taken at 110-130 min (P<0.02). The ratio alpha 12/alpha 23 still showed a significant relation (positive) with age but not with filtration function.

CONCLUSION

This error in the estimation of glomerular filtration rate to which delayed mixing leads will make its greatest impact when using the simplified slope-only technique, but can be minimized by delaying the first blood sample.

A direct in vivo measurement of 99mTc-methylene diphosphonate protein binding

Quantitative studies of the kinetics of 99mTc-methylene diphosphonate (99mTc-MDP) in metabolic and metastatic bone disease require the measurement of free tracer in plasma to derive the input function. We describe a simple method of determination of free 99mTc-MDP in vivo based on measurements of the ratio of the renal plasma clearances of total 99mTc-MDP and 51Cr-ethylenediaminetetraacetic acid (51Cr-EDTA). The method is based on evidence that free MDP is cleared through the kidneys by glomerular filtration. Measurements of the fraction of free 99mTc-MDP were made between 0 and 4 h after injection in 70 postmenopausal women enrolled in a study of the effect of hormone replacement therapy on the whole-skeleton plasma clearance of 99mTc-MDP (K(bone)). The glomerular filtration rate (GFR) was measured simultaneously from the plasma clearance of 51Cr-EDTA. The mean fractions (and SD) of free MDP measured were 0.757 (0.050), 0.663 (0.062), 0.550 (0.052) and 0.472 (0.053), respectively, at 17, 90, 150 and 210 min after injection. The results agreed closely with data using protein precipitation with trichloroacetic acid. Between 2 and 4 h after injection, the biological half-life of free 99mTc-MDP in plasma was 92 min, compared with 540 min for bound MDP. Highly significant relationships were found between the fraction of free MDP measured in each patient at each of the four time points and the total plasma clearance of free 99mTc-MDP (K(total)=GFR+K(bone)), such that a larger value of K(total) was associated with a smaller fraction of free MDP. Multivariate regression analysis confirmed that this relationship held individually for both GFR and K(bone). A strong inverse relationship was found between K(total) and the plasma concentration of free 99mTc-MDP, but a much weaker relationship with the bound MDP concentration, a finding that is consistent with the slow re-equilibration of bound MDP in the circulation. The results confirm that the fraction of free 99mTc-MDP varies with time and shows significant differences between individuals, which are dependent on GFR and K(bone) amongst other factors.

[Evaluation of glomerular filtration rate in clinical practice]

Glomerular filtration rate (GFR) is the most frequently used parameter to evaluate the renal function. GFR may be estimated with serum creatinine, creatinine clearance based on 24 hours urine collection or Cockcroft formula. All these methods have bias. Other approaches have thus been proposed. The limitations and advantages of isotopic methods and recent mathematical approaches (MDRD formula) are reviewed.

Conventional measurements of GFR using 51Cr-EDTA overestimate true renal clearance by 10 percent

It is widely believed that measurement of the area under the plasma clearance curve (AUC) following a single intravenous injection of chromium-51 labelled ethylene diamine tetra-acetic acid ((51)Cr-EDTA) is a gold standard method for determining glomerular filtration rate (GFR). However, there are reports that (51)Cr-EDTA may have a significant extrarenal clearance. The aim of this study was to identify the non-renal component of (51)Cr-EDTA plasma clearance contributing to the AUC measurement of GFR. Seventy healthy postmenopausal women (mean age 60 years, range 45-79 years) were injected with 3 MBq (51)Cr-EDTA and 0.25 MBq iodine-125 labelled human serum albumin and 11 blood samples taken between 0 and 4 h through an indwelling venous cannula. For the first 21 subjects, two complete urine collections were made 0-2 h and 2-4 h after injection, and for the final 49 patients, four 1-h urine collections were made. The mean (51)Cr-EDTA total plasma clearance was 84 ml/min (range 50-132 ml/min). The mean ratio (SEM) of urine to total clearance determined from the cumulative 1-, 2-, 3- and 4-h data was 0.903 (0.018), 0.891 (0.013), 0.898 (0.011) and 0.899 (0.010) respectively and remained constant despite the mean urine concentration decreasing from 122% to 15%/litre during this period. A least squares fit to data from the 238 individual urine collections was used to determine the fraction of the total plasma clearance attributable to renal clearance, alpha(0), and the residual urine volume, delta V. The results were alpha(0)=0.910 (95% CI: 0.889-0.932) and delta V=14 ml (95% CI: -4 to +34 ml). The overestimation of the true renal clearance of (51)Cr-EDTA by the AUC method is believed to be due to the failure of the plasma clearance curve to reach the true terminal exponential by 2 h after injection as usually assumed. As a result, conventional measurements of GFR using (51)Cr-EDTA overestimate the true renal clearance of tracer by approximately 10%.

Relationship of renal function to homocysteine and lipoprotein(a) levels: the frequency of the combination of both risk factors in chronic renal impairment

BACKGROUND

Total homocysteine (tHcy) and lipoprotein(a) [Lp(a)] levels have been recognized as risk factors for vascular disease. The combination of elevated tHcy and Lp(a) levels may be particularly atherogenic, although no study has examined the prevalence of the combination of both risk factors in patients with chronic renal impairment.

METHODS

One hundred ninety-seven patients with renal impairment were studied. Patients had glomerular filtration rate (GFR) measured by clearance of chromium 51-labeled EDTA. Blood was obtained for the determination of tHcy, Lp(a), and apolipoprotein(a) [apo(a)] isoform levels.

RESULTS

Patients were divided into five groups according to GFR. Mean tHcy levels in the five groups were as follows: GFR less than 10 mL/min, 30.2 +/- 9.8 (SD) micromol/L; GFR of 10 to 20 mL/min, 26.6 +/- 10.5 micromol/L; GFR of 20 to 30 mL/min, 23.9 +/- 8.6 micromol/L; GFR of 30 to 45 mL/min, 22.2 +/- 8.6 micromol/L; and GFR of 45 to 75 mL/min, 18.2 +/- 9.1 micromol/L compared with control levels of 12.7 +/- 4.6 micromol/L. There was a progressive increase in median Lp(a) levels with declining renal function: median Lp(a) levels for those with a GFR less than 10 mL/min were 37.1 mg/dL (range, 0.6 to 156.0 mg/dL); GFR of 10 to 20 mL/min, 30.3 mg/dL (range, 2.6 to 163.7 mg/dL); GFR of 20 to 30 mL/min, 26.1 mg/dL (range, 0.0 to 164.0 mg/dL); GFR of 30 to 45 mL/min, 20.9 mg/dL (range, 0.0 to 99.8 mg/dL), and GFR of 45 to 75 mL/min, 16.8 mg/dL (range, 2.1 to 81.0 mg/dL) compared with control values of 12.5 mg/dL (range, 0.0 to 88.7 mg/dL).

CONCLUSION

Defining hyperhomocysteinemia as tHcy levels greater than the 90th percentile of controls and elevated Lp(a) level as greater than 30 mg/dL, the frequency of the combination increased with declining renal function. Fifty-eight percent of patients with a GFR less than 10 mL/min had both hyperhomocysteinemia and elevated Lp(a) levels, and even in patients with mild renal impairment, 20% of patients had both risk factors present.

Vasoactive agents induce cytotoxicity in cultured human penile smooth muscle cells

OBJECTIVES

To evaluate the direct in vitro cytotoxicity of vasoactive agents (papaverine, phentolamine, and prostaglandin E(1) [PGE(1)]) to human penile cavernosal smooth muscle cells. Intracavernous pharmacotherapy with vasoactive agents for male erectile dysfunction has been associated with long-term complications such as a reduction in penile smooth muscle content and fibrosis.

METHODS

Human penile cavernosal tissue explants (1 to 2 mm(3) size) were obtained with proper institutional review board approval from patients undergoing penile prosthesis implantation. Primary culture was initiated in Dulbecco's modified Eagles medium containing 10% fetal bovine serum, and monolayer cavernosal cells were grown in 48-well tissue culture dishes. At 60% to 80% confluence, cells were labeled overnight with (51)Na(2)CrO(4) (1.5 microCi) and then incubated with therapeutic concentrations of papaverine (1.5 to 30 mg/mL), phentolamine (0.5 mg/mL), and PGE(1) (5 microg/mL) alone, as well as in combination, for 30 minutes at 37 degrees C. At the end of incubation, an aliquot of supernatant was collected in scintillation vials. The release of cell-free chromium in supernatants was determined in a liquid scintillation counter, and results were expressed as the percentage of cytotoxicity.

RESULTS

Papaverine induced a significant dose-dependent increase in chromium release from the cavernosal cells. At therapeutic concentrations, papaverine (30 mg/mL) produced up to 60% cytotoxicity; PGE(1) (5 microg/mL) resulted in 40% toxicity. The combination of papaverine with either PGE(1) or phentolamine had a cumulative toxic effect, and maximal toxicity (70%) was observed with the triple combination.

CONCLUSIONS

Papaverine-induced cytotoxicity to cavernosal smooth muscle cells may contribute to the fibrosis and loss of smooth muscle content associated with the intracavernous pharmacotherapy. Quantitative evaluation of in vitro cytotoxicity in human cavernosal smooth muscle cell culture may be important in the development of new intracavernosal vasoactive agents.

Activated polymorphonuclear cells increase sickle red blood cell retention in lung: role of phospholipids

This study investigates the role of the activated polymorphonuclear cell (APMN) products on sickle red blood cell (SRBC) retention/adherence in the pulmonary circulation. Isolated rat lungs were perfused with (51)Cr-labeled normal RBCs (NRBC) or SRBCs (10% hematocrit) suspensions +/- PMNs. Specific activities of lung and perfusate were measured and retention (the number of SRBC/g lung) was calculated. SRBC retention was 3.5 times greater than NRBC retention. PMN activation was required to increase SRBC retention. Supernatants from APMN increased SRBC retention, which suggested soluble products such as oxidants, PAF, and/or leukotriene (LTB(4)) are involved. Heat inactivation of PMN NADPH oxidase had no effect on retention. Whereas neither platelet-activating factor (PAF) nor LTB(4) (secreted by APMN) increased SRBC retention, PAF+LTB(4) did. The PAF antagonist, WEB-2170, attenuated SRBC retention mediated by PAF+LTB(4) and APMNs. Similarly, zileuton (5-lipoxygenase inhibitor) attenuated APMN-mediated SRBC retention. We conclude the concomitant release of PAF and LTB(4) from APMN is involved in the initiation of microvascular occlusion by SRBCs in the perfused rat lung.

Puromycin aminonucleoside damages the glomerular size barrier with minimal effects on charge density

Puromycin aminonucleoside (PAN) has been suggested to reduce glomerular charge density, to create large glomerular "leaks," or not to affect the glomerular barrier. Therefore, we analyzed glomerular charge and size selectivity in vivo and in isolated kidneys perfused at 8 degrees C (cIPK) in control and PAN-treated rats. The fractional clearances (theta) for albumin and Ficoll of similar hydrodynamic size were 0.0017 +/- 0.0004 and 0.15 +/- 0.02, respectively, in control cIPKs. Two-pore analysis gave similar results in vivo and in vitro, with small- and large-pore radii of 47-52 and 85-105 A, respectively, in controls. Puromycin increased the number of large pores 40-50 times, the total pore area over diffusion distance decreased by a factor of 25-30, and the small-pore radius increased by 33% (P < 0.001 for all comparisons of size selectivity and theta). The effect of PAN was less dramatic on the estimated wall charge density, which was 73% of that of controls. We conclude that puromycin effectively destroys the glomerular size barrier with minimal effects on charge density.

The trail of chromium(III) in vivo from the blood to the urine: the roles of transferrin and chromodulin

The chromium-binding oligopeptide chromodulin (also known as low-molecular-weight chromium-binding substance) has been shown to activate the tyrosine kinase activity of the insulin receptor in response to insulin and has been proposed to be part of a novel autoamplification mechanism for insulin signaling. The model requires that Cr3+ be moved from the blood to insulin-sensitive tissues in response to insulin and subsequently be lost in the urine as chromodulin; however, the model has not been tested by in vivo studies. In vivo studies with rats have shown that the iron transport protein transferrin serves as the major chromic ion transport agent and that this transport is stimulated by insulin. The ion is transported to a variety of tissues, while liver and kidneys are the major target. In hepatocytes, chromodulin occurs in appreciable levels in the cytosol and in the nucleus. Apochromodulin levels appear to be maintained under homeostatic control, although the only detectable form of urinary chromium is probably chromodulin. Increases in urinary chromium loss in response to insulin are reflected by increases in chromodulin, establishing a direct link between carbohydrate metabolism and the oligopeptide.

Interstitial exclusion of positively and negatively charged IgG in rat skin and muscle

Volume exclusion, i.e., the space not available for a specific probe, may be dependent on the probe charge. Therefore, interstitial exclusion was measured for positively and negatively charged immunoglobulin (IgG) in skin and muscle of rats by using a continuous infusion method (30). Steady-state concentration of (125)I-labeled IgG 1 (pI = 8.7) and (131)I- labeled IgG 4 (pI = 6.6) was maintained by infusion of tracer for 120-168 h with an implanted osmotic pump. At the end of the infusion period and before tissue sampling, the rat was anesthetized and nephrectomized, and (51)Cr-labeled EDTA was injected and allowed 4 h for equilibration to measure interstitial fluid volume (V(i)). Interstitial fluid was isolated from skin and muscle by using nylon wicks implanted post mortem. The relative IgG available space was measured as the ratio between labeled IgG and (51)Cr-labeled EDTA wick fluid equivalent spaces, and relative excluded volume fraction (V(e)/V(i)) was calculated as 1--V(a)/V(i). V(e)/V(i) in hindlimb skin averaged 0.37 +/- 0.05 (SE) and 0.65 +/- 0.06 (P < 0.01) for IgG 1 and 4, respectively, with corresponding figures of 0.24 +/- 0.05 and 0.51 +/- 0.04 (P < 0.01) in hindlimb muscle (n = 9 for both tissues). These experiments suggest that fixed negative charges, most likely glycosaminoglycans, influence distribution of macromolecules in the interstitium and therefore affect interstitial fluid balance.

Influence of errors in sampling time and in activity measurement on the single sample clearance determination

INTRODUCTION

Plasma clearance rate of 51Cr-EDTA estimated by using one blood sample is commonly used for the calculation of glomerular filtration rate.

AIM

To estimate the error on single-sample clearance determination induced by errors in sampling time and activity measurement, and to compare it with the error observed on the clearance determination obtained using the slope-intercept method.

METHODS

Forty-five adult patients were chosen from a data base of 51Cr-EDTA plasma clearance values determined by using two blood samples taken around 2 and 4 h. Patients were selected in such a way as to include clearances from 30 ml.min-1 to 155 ml.min-1, with steps of 3 ml.min-1. Based on the slope and the intercept of the slope with the y-axis, the plasma concentration at exactly 2 and 4 h was determined. Normally distributed random errors were then introduced in the sampling time (SD of 0, 1 and 2 min) as well as in the activity measurement (SD of 0, 1, 2 and 5%). Then, clearance was calculated using two single-sample methods (i.e. the algorithms of Groth and Tauxe), and the slope-intercept method, which requires two blood samples. For each setting, the simulation was repeated 200 times. The effects on clearance of a random error on the time sampling and/or the activity measurement were then evaluated.

RESULTS

The error on single-sample clearance induced by a 2 min error in sampling time associated with a 5% error in activity measurement was negligible. For all clearance levels, the SD of the error on the calculated clearance was less than 3.8 ml.min-1. Whatever algorithm was chosen, the errors on the single-sample clearance were systematically lower than those observed with the slope-intercept method, for the whole clearance range.

CONCLUSION

Errors in sampling time and in activity measurement induced only a very small error on the single-sample EDTA clearance, which is systematically lower compared to that observed on the slope-intercept method using two blood samples.

A simple and inexpensive preparation of [(51)Cr]-MAA particles

The feasibility of preparing [(51)Cr]-MAA was investigated using an MAA cold kit and commercially available sodium [(51)Cr]chromate solutions. Of different conditions tested, the best required an addition of a low level of sodium dithionite to achieve a radiolabeling efficiency of 44%. The product was purified by centrifugation to give [(51)Cr]-MAA with 99 +/- 1% radiochemical purity (RCP) comprised of >94% radioactive particles >10 microm, and resulted in a rat biodistribution with >80% in the lungs. [(51)Cr]-MAA is inexpensive, easily and conveniently prepared by this procedure.

Iohexol as a marker of glomerular filtration rate in patients with diabetes: comparison of multiple and simplified sampling protocols

AIMS

To report on the reproducibility of iohexol glomerular filtration rate (GFR) estimation, to compare the plasma clearance of iohexol with that of[51Cr]EDTA and to evaluate the reliability of reduced sampling schedules in estimating GFR in Type 1 and Type 2 diabetes mellitus.

METHODS

Agreement was assessed in 15 Type 1 and 26 Type 2 diabetics with creatinine ranging from 53 to 564 micromol/l.

RESULTS

The regression between multiple-sample iohexol and[51Cr]EDTA clearances was 0.999 in Type 1 and 0.987 in Type 2 diabetes (P < 0.0001 for both). A seven-sample design and the three-sample approach by Brøchner-Mortensen were validated by comparison with the full-sample schedule in 87 patients (51 Type 1, 36 Type 2). Full-sample GFR was 80.3 +/- 43.8, seven-sample 79.5 +/- 43.9 (r = 0.990) and three-sample 79.8 +/- 45.2 ml.min-1.1.73 m-2 (r = 0.972). The coefficients of variation of GFR were 2.7 +/- 1.4% and 3.8 +/- 1.9% for the full-sample and the seven-sample approaches, respectively, and significantly higher for the three-sample design (6.9 +/- 3.4%, P = 0.0001).

CONCLUSIONS

After iohexol injection, the Brøchner-Mortensen schedule does not provide an accurate estimate of GFR. The seven-sample approach gives acceptable errors and allows a good estimate of GFR throughout a wide range of renal function.

Use of an orally administered combined sugar solution to evaluate intestinal absorption and permeability in cats

OBJECTIVE

To evaluate intestinal permeability and absorption in healthy cats in association with diet and normal intestinal microflora.

ANIMALS

6 healthy domestic shorthair cats.

PROCEDURE

A sugar solution containing D-xylose, 30-methyl-D-glucose, L-rhamnose, lactulose, and 51Cr-EDTA was administered intragastrically to healthy cats, and urinary excretion of ingested sugars was determined 5 hours after administration. After the same cats had received metronidazole for 1 month, the study was repeated. A final study was performed while cats were maintained on a new diet differing in composition and processing.

RESULTS

Lactulose-to-rhamnose ratios, reflecting intestinal permeability, were higher in cats, compared with values for humans or dogs, and values obtained before and after metronidazole administration (mean +/- SEM; before, 0.40 +/- 0.08; after, 0.45 +/- 0.09) were not significantly different. Intestinal absorption also was unaltered after antibiotic administration, and the xylose-to-glucose ratio was 0.70 +/- 0.03 before and 0.71 +/- 0.06 after metronidazole administration. Sugar recovery did not differ significantly while cats were maintained on canned or dry food.

CONCLUSIONS AND CLINICAL RELEVANCE

Reference ranges were established for the percentage urinary recovery of orally administered D-xylose, 3-0-methyl-D-glucose, L-rhamnose, lactulose, and 51Cr-EDTA obtained after 5 hours in healthy cats. The intestines of cats appear to be more permeable than those of other species, although the normal bacterial microflora does not appear to influence the integrity or function of the feline intestine, because values obtained for the measured variables before or after antibiotic administration were not significantly different. In addition, differences were not detected when the diet was completely altered.

Intravascular circulation and distribution of human 51Cr-DBBF stroma-free hemoglobin, 51Cr-plasma, 51Cr-saline, 59FE-plasma, and 125I-albumin in the mouse

Male B6C3HF1 mice were infused with human 51Cr-labeled DBBF (bis 3,5-dibromosalicyl fumarate) crosslinked stroma-free hemoglobin (SFH). In the first hour following SFH infusion, 11.2% of the infused radioactivity was found in the skin, 11.4% in muscle, 9.1% in the skeleton, and 5% in the liver. Twenty-four hours after infusion, 15.4% of the radioactivity was found in the skin, 10.3%, in the muscle, 16.6% in the skeleton, and 6.7% in the liver. The circulation and distribution of 51Cr-labeled DBBF-SFH were compared with levels of 51Cr labeled plasma, 51Cr in saline, 59Fe labeled plasma, and 125I albumin. The radioactivity in the blood was similar for 51Cr-DBBF-SFH, 51Cr-plasma, and 59Fe-plasma. During the 24-hour post-infusion period, extravascular distribution of the 51Cr-saline, 51Cr-plasma, and 125I albumin within the organs was similar to that of 51Cr-DBBF-SFH, with the highest levels being in skin, muscle, skeleton and liver, and no increase in the levels in the lung or spleen. The distribution of 59Fe compared to that of 51Cr-DBBF, 51Cr-plasma, 51Cr-saline, and 125I albumin can be explained by the fact that 59Fe is utilized in the production of new red blood cells.

Permeability of the rat small intestinal epithelium along the villus-crypt axis: effects of glucose transport

BACKGROUND & AIMS

The aim of this study was to elucidate the permeability characteristics of the epithelium along the villus-crypt axis and investigate the effect of glucose transport on these characteristics along this axis.

METHODS

The disappearance rates of (14)C-mannitol and (51)Cr-EDTA or (3)H-inulin were determined as clearance (Cl(x)) from a recirculating perfusion system of the jejunal lumen in anesthetized rats. Net fluid transport was varied over a large range by exchanging mannitol with glucose in the perfusate solution and by inhibition of nervously mediated secretory processes with hexamethonium. The perfusion rate was 0.5 or 0.2 mL/min.

RESULTS

Cl(Man) enhanced significantly with increasing net fluid transport (secretion 8.50+/-1.88, to absorption 16.72+/-1.75 microL x min(-1) x g(-1)) and with glucose perfusates. Cl(Cr-EDTA) was constant irrespective of net fluid transport and was reduced to insignificant values at a perfusion rate of 0.2 mL/min. Cl(In) was not different from zero.

CONCLUSIONS

The absorbing apical part of the villus contains small pores (radius, <6 A) allowing passive transport via solvent drag of, e.g., monosaccharides, whereas the pores in the crypts are large (50-60 A) and inaccessible to the luminal content. The basal part of the villus contains medium-sized pores (10-15 A) through which no solvent drag occurs. Active glucose transport in the rat mainly increases the number of small pores accessible for passive transport, whereas the size of these pores seems to stay constant.

Renal blood flow, early distal sodium, and plasma renin concentrations during osmotic diuresis

Inconsistencies in previous reports regarding changes in early distal NaCl concentration (ED(NaCl)) and renin secretion during osmotic diuresis motivated our reinvestigation. After intravenous infusion of 10% mannitol, ED(NaCl) fell from 42.6 to 34.2 mM. Proximal tubular pressure increased by 12.6 mmHg. Urine flow increased 10-fold, and sodium excretion increased by 177%. Plasma renin concentration (PRC) increased by 58%. Renal blood flow and glomerular filtration rate decreased, however end-proximal flow remained unchanged. After a similar volume of hypotonic glucose (152 mM), ED(NaCl) increased by 3.6 mM, (P < 0.01) without changes in renal hemodynamics, urine flow, sodium excretion rate, or PRC. Infusion of 300 micromol NaCl in a smaller volume caused ED(NaCl) to increase by 6.4 mM without significant changes in PRC. Urine flow and sodium excretion increased significantly. There was a significant inverse relationship between superficial nephron ED(NaCl) and PRC. We conclude that ED(Na) decreases during osmotic diuresis, suggesting that the increase in PRC was mediated by the macula densa. The results suggest that the natriuresis during osmotic diuresis is a result of impaired sodium reabsorption in distal tubules and collecting ducts.

Effect of efferent duct ligation on the function of the blood-testis barrier in rats

The function of the blood-testis barrier has been assessed from the ratio of the Cr-EDTA space in the parenchyma to the measured interstitial volume in the testes of rats at various times after unilateral ligation of the efferent ducts. The barrier remained effective during the phase of fluid accumulation and testicular mass gain, which was linear for at least 24 h, but the testis mass began to decrease between 32 and 40 h after efferent duct ligation, and the Cr-EDTA space at 40 and 48 h after efferent duct ligation exceeded the volume of the interstitial tissue. This finding indicated that, at these times, the barrier to Cr-EDTA, which is normally excluded from the tubules, had broken down and the marker was entering the tubules. Thereafter, the Cr-EDTA space decreased again to be less than the interstitial tissue volume, indicating a restoration of the barrier function, although degeneration of the seminiferous epithelium continued to become more obvious. The present study is the first report of a reversible breakdown of the barrier, but the relevance of the breakdown to the effects on spermatogenesis requires further study.

Autonomic dysfunction and urinary albumin excretion rate are associated with an abnormal blood pressure pattern in normotensive normoalbuminuric type 1 diabetic patients

OBJECTIVE

To analyze the role of autonomic function and other possible factors associated with a blunted fall in nocturnal blood pressure.

RESEARCH DESIGN AND METHODS

A total of 39 normotensive normnoalbuminuric type 1 diabetic patients were studied. Glomerular filtration rate (51Cr-EDTA technique), extracellular volume (51Cr-EDTA distribution volume), and urinary albumin excretion rate (UAER) (by radioimmunoassay) were measured. The subjects' 24-h ambulatory blood pressure and a 24-h electrocardiogram were recorded simultaneously Heart rate variability was calculated in the time domain for 24 h, in the frequency domain at night, at rest in the supine position, and during tilt. Patients were classified according to diastolic blood pressure (dBP) night/day ratio as dipper patients (< or =0.9) and nondipper patients (>0.9).

RESULTS

Nondipper patients presented a higher low-frequency (LF) component (a sympathetic index) and higher LF/high-frequency (HF) ratio during sleep than dipper patients (0.29 +/- 0.12 vs. 0.19 +/- 0.10 normalized units [n.u.], P = 0.008; and 0.98 +/- 0.53 vs. 0.55 +/- 0.45 n.u., P = 0.007, respectively). At rest, the LF component in nondipper patients (0.38 +/- 0.13 n.u.) was higher than in dipper patients (0.27 +/- 0.12 n.u., P = 0.04). After the tilt, nondipper patients did not show an increase in the LF component (P = 0.32), but in dipper patients, the increase was significant (P = 0.001). In both groups, tilting promoted a decrease in the HF component (a parasympathetic index). In a stepwise multiple linear regression analysis, the LF component during sleep and the UAER accounted for 24% of the variability in the dBP night/day ratio.

CONCLUSIONS

The predominance of sympathetic activity and increased levels of UAER, although within the normal range, are associated with a blunted fall in nocturnal dBP in normoalbuminuric normotensive type 1 diabetic patients.

Evaluation of gastrointestinal toxicity of ibuprofen using surrogate markers in rats: effect of formulation and route of administration

OBJECTIVE

To elucidate the mechanism of gastrointestinal (GI) toxicity of ibuprofen and to examine the effect of altered site of drug release using gastroduodenal and intestinal permeability tests in the rat model.

METHODS

Adult male Sprague-Dawley rats were administered (n = 6 per group) either: (1) 100 mg/kg immediate or sustained release ibuprofen; (2) 100 mg/kg immediate release and ibuprofen lysinate; or (3) 100 mg/kg or 200 mg/kg ibuprofen po or s.c. Upper and lower GI permeability as a surrogate marker of toxicity were determined at pre-determined times using the urinary excretion of orally administered sucrose and 51Cr-EDTA permeability probes, respectively.

RESULTS

Ibuprofen administration resulted in a dose-dependent increase in both upper and lower permeability of the GI tract. Both immediate and sustained release preparations of ibuprofen increased upper and lower GI permeability with no shift of toxicity to the site of drug release. Ibuprofen lysinate also induced significant increased upper and lower GI permeability comparable to immediate release ibuprofen. Oral doses were not more toxic than s.c. doses.

CONCLUSION

Ibuprofen-induced increased GI permeable appears to be independent of the type of formulation and route of administration. This indicates that, contrary to some other nonsteroidal anti-inflammatory drugs, ibuprofen's effect on GI permeability is mainly systemic and the direct local effect contributes minimally to its overall GI toxicity. Ibuprofen may be a suitable candidate for sustained release formulations since its effect may be prolonged without the danger of a shift of side effect from the upper to the lower GI tract.

Total plasma clearance of 51Cr-EDTA: variation with age and sex in normal adults

Although inulin clearance measured during constant infusion is still considered the reference method, single-injection of 51Cr-EDTA with subsequent plasma sampling has become the most popular technique for the routine assessment of glomerular filtration rate. Despite the fact that the technique has been in use for 30 years, there are only a few reports of normal values calculated directly from 51Cr-EDTA data and normal ranges have generally been produced by conversions of inulin data. The aim of this study was to measure the variation in total plasma clearance, calculated directly from 51Cr-EDTA measurements, in normal males and females, of Saudi Arabian origin, over a wide range. Altogether, 201 potential kidney donors aged 16-60 years were studied. No statistically significant association of total plasma clearance with age or sex could be demonstrated; however, predictive equations suggesting a small decline in total plasma clearance with age were developed. The figures presented suggest that the reduction in total plasma clearance of 51Cr-EDTA with age is relatively shallow up to the age of at least 60 years and that normal ranges produced by conversion of inulin data may overestimate the decline with age.

Assessment of long-term bronchiolar clearance of particles from measurements of lung retention and theoretical estimates of regional deposition

Twelve healthy nonsmokers inhaled monodisperse Teflon particles labelled with 51Cr (half-life 27.8 days) with an aerodynamic diameter (dae) of 6.1 microns, 5 at a normal flow, 0.5 L/s, and 7 at an extremely slow flow, 0.05 L/s. Lung retention after 24 hours was measured for about 6 months and could be well described by a 2-component exponential function. After the normal inhalation, 14% of the particles retained after 24 hours cleared with a half-time of 3.7 days and 86% with a half-time of 217 days. After the slow inhalation, 35% of the particles retained after 24 hours cleared with a half-time of 3.6 days and 65% with a half-time of 170 days. Deposition was calculated using 3 different models including the recent Human Respiratory Tract Model (HRTM), adopted by the International Commission on Radiological Protection (ICRP), and a model based on Monte Carlo particle transport, together with an asymmetric lung model. Generally, the 3 models agreed fairly well and predicted a considerably higher deposition in the bronchiolar region (generations 9-15) at the slow flow than at the normal flow. Together, the experimental data and the predictions of the deposition models indicate that about 40% of the particles deposited in the conducting airways during the slow inhalation were retained after 24 hours. They also strongly indicate that the particles which cleared with a half-time of about 4 days were mainly deposited in the bronchiolar region, and that about 25% of the particles deposited in the bronchiolar region cleared in this phase. The experimental data agreed quite well with the HRTM predictions made using its default parameter values for slow clearance in the bronchial tree.

Absolute 24 h quantification of 99Tcm-DMSA uptake in patients with severely reduced kidney function: a comparison with 51Cr-EDTA clearance

The aim of this study was to determine whether absolute 24 h DMSA uptake measurements (%DMSA) correlate well with 51Cr-EDTA clearance measurements in patients with severely reduced kidney function (SRKF). Between 1990 and 1997, 55 of 482 patients who underwent EDTA clearance measurements also underwent %DMSA within 1 week. Of these, 31 were women and 24 were men (mean age 60 years; range 19-77 years). EDTA clearance was determined using the slope-intercept method. Absolute depth- and background-corrected %DMSA were determined 24 h following the injection of 185 MBq per 1.73 m2 freshly prepared 99Tcm-DMSA. All patients had EDTA clearance < or = 60 ml.min-1. Eighteen patients (group A: 9 men and 9 women, mean age 55.8 years, range 28-73 years) had EDTA clearance > 20 ml.min-1 (mean +/- S.D. = 30.9 +/- 13.8 ml.min-1), whereas 37 patients (group B: 22 women and 15 men, mean age 62.0 years, range 19-77 years) had EDTA clearance < 20 ml.min-1 (mean +/- S.D. = 10.2 +/- 6.6 ml.min-1). EDTA clearance correlated well with %DMSA for the patients as a whole and for group A (r = 0.87, P = 0.73; r = 0.79, P = 0.0001 respectively). The regression equation suggests that %DMSA is not a marker of early renal dysfunction. In group B, the r-value (r = 0.48, P = 0.004) suggests that %DMSA is reliable as a marker of severe renal dysfunction to the extent that it provides rough information. In conclusion, %DMSA may not be used as a marker of early renal impairment. Additionally, in patients with severely reduced kidney function (EDTA clearance < 20 ml.min-1), it only provides a rough estimate.

Cerebral blood volume measured using near-infrared spectroscopy and radiolabels in the immature lamb brain

Near-infrared spectroscopy (NIRS) is a technique that is increasingly being used for the noninvasive measurement of cerebral blood volume (CBV) in newborn infants, but it has not been fully validated against established methods. These experiments in immature lambs (gestation 92+/-1 d, mean+/-SEM) compared CBV measured using NIRS-derived estimates of oxygenated Hb (n = 5) with CBV estimated with radiolabeled indicators (125I-labeled serum albumin and 51Cr-labeled red blood cells, n = 10). Total brain CBV (mL/100 g tissue) measured using NIRS was 2.5+/-0.2 compared with 2.5+/-0.2 using radiolabels (NS). Regional tissue plasma, red blood cells, and whole blood volumes from radiolabels varied significantly (p < or = 0.05) throughout the brain. Whole blood volume (mL/100 g tissue) was largest in choroid plexus (16.2+/-2.1) and least in white matter (0.7+/-0.1) with a significant hierarchy evident among regions: choroid plexus > cerebellum > cortex > brain stem = midbrain > white matter. Regional plasma and red blood cell distributions were similar to whole blood, being highest in choroid plexus (13.0+/-1.6 and 3.2+/-0.9, respectively), and least in white matter (0.8+/-0.1 and 0, respectively). These data from the immature lamb brain indicate that total CBV measured with NIRS is essentially identical with the volumes obtained using intravascular radiolabels. Among cerebral regions, white matter contributes little to the global blood volume measured with NIRS because its red blood cell content is very low.

Evaluation of renal function in low-dose cyclosporine-treated patients using technetium-99m diaminocyclohexane: a cationic tubular excretion agent

Technetium-99m diaminocyclohexane (DACH) is a new tubular agent excreted via a cationic transport mechanism, like cyclosporine-A (CsA). It is expected that 99mTc-DACH will permit effective assessment of tubular function in CsA-treated patients. To establish the pharmacokinetic characteristics of 99mTc-DACH and to ascertain whether this new agent is useful in CsA-treated patients, 11 healthy volunteers and 15 CsA-treated patients underwent renal imaging and clearance studies using 99mTc-DACH and chromium-51 ethylene diamine tetra-acetic acid (EDTA). 99mTc-DACH yielded satisfactory dynamic renal images in all participants. The mean plasma clearance of 99mTc-DACH was significantly greater than that of 51Cr-EDTA in volunteers (109.4¿19.7 ml/min versus 86.6 +/- 13.7 ml/min, P<0.05). However, the urinary excretion of 99mTc-DACH at 90 min was significantly lower than that of 51Cr-EDTA (46.1% +/- 9.3% versus 53.1% +/- 8.6%, P<0.05), most probably due to its partial parenchymal retention. The elimination half-life of 99mTc-DACH was significantly increased in CsA-treated patients in comparison to volunteers, and consequently the plasma clearance values were significantly suppressed in these patients, in contrast to 51Cr-EDTA and endogenous creatinine clearance values. In conclusion, our findings indicate that 99mTc-DACH, as a sensitive marker of cationic tubular function, could be used to monitor renal haemodynamics in patients receiving CsA treatment.

Chromium-51-EDTA clearance in adults with a single-plasma sample

In 1996, a committee on renal clearance recommended a mean sojourn time-based methodology for single-sample determination of plasma clearance of 99mTc-diethylenetriamine pentaacetic acid (DTPA) to be used on adults if the patient's glomerular filtration rate (GFR) is suspected to be >30 ml/min. The main purpose of this study was to derive a mean sojourn time-based formula for calculation of 51Cr-ethylenediamine tetraacetic acid (EDTA) clearance in adults.

METHODS

Two groups of patients with 51Cr-EDTA clearance (Cl) between 16 and 172 ml/min were studied. In Group I (n = 46), reference Cl was determined as a multiplasma sample, single-injection method (ClSM). Sixteen blood samples were drawn from 0 until 5 hr after a single intravenous injection of 51Cr-EDTA. In Group II (n = 1046), reference Cl was determined by the Brøchner-Mortensen four-sample clearance method (ClBM). The plasma time-activity curves of Group I were used to derive two mean sojourn time-based formulas (Formulas 1 and 2) for calculation of a single-sample clearance. Formula 1 was derived from the entire time-activity curve, whereas the derivation of Formula 2 used only the final slope of the time-activity curve. The accuracy of the two formulas and the Christensen and Groth 99mTc-DTPA formula was tested on Group II.

RESULTS

Chromium-51-EDTA Cl calculated by Formula 1 was almost identical to the Cl calculated by the reference Cl method (r = 0.982; SDdiff = 5.82 ml/min). Both 51Cr-EDTA Cl calculated by Formula 2 and by the 99mTc-DTPA formula showed close correlation with the reference method (r = 0.976, r = 0.985, respectively) but systematically overestimated GFR for the whole range of clearance values by 3.5 and 3.2 ml/min (p<0.001), respectively.

CONCLUSION

It is possible to get an accurate determination of 51Cr-EDTA Cl from a single-plasma sample in adults by the mean sojourn time methodology. The determination is marginally more accurate (p<0.001) if using a formula derived from the entire plasma time-activity curve than from only the final slope. The single-sample formula derived for determination of 99mTc-DTPA Cl tends slightly to overestimate GFR if used to calculate 51Cr-EDTA Cl.

Role of gap junctions in inhibiting ischemia-reperfusion injury of rat gastric mucosa

Gap junctional intercellular communication (GJIC) is known to be important in the maintenance of tissue homeostasis. However, the role of GJIC in gastric mucosa has not been well investigated. We tested the hypothesis that maintenance of GJIC protects rat gastric mucosa against ischemia-reperfusion (I/R) stress by using irsogladine, an activator of GJIC, and octanol, an inhibitor of GJIC. Intragastric perfusion with octanol before ischemia resulted in a significant increase in 51Cr-EDTA clearance after reperfusion. Intraduodenal pretreatment with irsogladine attenuated the increase in 51Cr-EDTA clearance produced by octanol in a dose-dependent manner. Epithelial gap junctions reacted with anticonnexin-32 monoclonal antibodies were not changed after I/R stress alone. Intragastric perfusion with octanol caused a significant reduction in immunoreactive connexin-32 spots, which was completely reversed by irsogladine. These results indicate that inhibition of GJIC weakens the barrier function of gastric mucosa and subsequently causes damage of the barrier function in combination with I/R. Facilitation of GJIC and maintenance of gap junctions protect gastric mucosal barrier functions by potentiating cellular integrity.

Capillary diffusion capacity and tissue distribution of pancreatic procolipase in rat

The permeability-surface area product of procolipase and its apparent distribution volume in rat tissues were assessed using a tissue uptake technique. Procolipase was investigated together with 51Cr-EDTA, used as an inert extracellular marker, and 131I-albumin, used as a plasma volume marker. The tissue uptake of procolipase seemed to occur by passive transport in most of the organs studied, such as in muscle, liver, lung, adipose tissue, adrenal glands, colon, and skin. However, throughout the gastrointestinal tract, except in the colon, there was a high uptake of procolipase, greatly exceeding that of 51Cr-EDTA. This was especially evident in the stomach, in which the procolipase uptake was nonsaturable within the experimental period. Also, in the central nervous system (CNS), there was evidence of specific, possibly carrier-mediated, transport. These results suggest that procolipase may have specific, conceivably receptor-mediated, transport pathways across the microvascular endothelium in the stomach, pancreas, duodenum, ileum, and the CNS.

Time course of gastrointestinal tract permeability to chromium 51-labeled ethylenediaminetetraacetate in healthy dogs

OBJECTIVES

To establish values for gastrointestinal tract permeation by chromium 51-labeled ethylenediaminetetraacetate (51Cr-labeled EDTA) in healthy adult dogs, and to evaluate the time course for 51Cr-labeled EDTA absorption over a 24-hour period after its administration, in an effort to define a shorter, more practical collection method.

ANIMALS

6 healthy adult mixed-breed dogs.

PROCEDURE

After an 18-hour nonfeeding period, each dog was given a solution containing 50 microCi of 51Cr-labeled EDTA in deionized water (10 ml/kg of body weight) by stomach tube. Complete urine collection was done at 2, 4, 6, and 24 hours after 51Cr-labeled EDTA administration. Five-milliliter samples of urine were counted for 15 minutes in a gamma counter, and radioactivity in urine was expressed as a percentage of the orally administered dose.

RESULTS

Median (range) 24-hour urinary recovery of 51Cr-labeled EDTA after 24 hours was 15.1 (12.7 to 20.3)%. Urine collected at 2, 4, and 6 hours contained 1.0 (0.2 to 3.5)%, 6.5 (2.2 to 8.7)%, and 10.0 (8.1 to 11.7)% of the administered 51Cr-labeled EDTA, respectively. Urine passed during the first 6 hours contained, on average, 67 (54 to 77)% of the total 24-hour urine recovery.

CONCLUSIONS

6-hour urinary recovery of 51Cr-EDTA provides a potential alternative to 24-hour recovery. This shorter collection period may more specifically reflect small intestinal permeability.

Intracavitary administration: pharmacokinetic advantages of macromolecular anticancer agents against peritoneal and pleural carcinomatoses

BACKGROUND

Pleural and peritoneal carcinomatoses are quite difficult to control in patients with advanced cancer. We have devised a suitable formulation of anticancer agents to be injected by the intracavitary route.

MATERIALS AND METHODS

The pharmacokinetics of macromolecular anticancer agent, copoly(styrene/maleic acid)-conjugated neocarzinostatin (smancs) and radiolabeled albumin were studied after intraperitoneal administration to ascitic tumor-bearing rats and mice, and were compared with the pharmacokinetics of other low-molecular-weight anticancer agents, mitomycin C (MMC) and doxorubicin (DOX).

RESULTS

Pharmacokinetic analyses indicated that smancs showed a much higher drug concentration for a longer time in the peritoneal cavity, and a much lower drug concentration in the blood circulation than did MMC or DOX. The cavity/blood ratios of the area under the concentration curve (AUC), of smancs, bovine serum albumin (BSA), DOX, and MMC were 9.69, 7.06, 1.38, 1.15, respectively.

CONCLUSION

These results suggest that macromolecular agents are cleared more slowly from the cavitary compartment and remain there at a high concentration while the blood concentration remains low.

Interaction between neurokinin A, VIP, prostanoids, and enteric nerves in regulation of duodenal function

Neurokinin A (NKA) induces duodenal motility and increases mucosal permeability and bicarbonate secretion in the in situ perfused duodenum in anesthetized rats. In the present study, the NKA-induced increase in mucosal permeability was potentiated by luminal perfusion with lidocaine and diminished by vasoactive intestinal peptide (VIP) but unaltered by elevated intraluminal pressure. Elevation of intraluminal pressure, however, potentiated the stimulatory effect of NKA on bicarbonate secretion. In contrast, the tachykinin decreased the rate of alkalinization in rats subjected to elevated intraluminal pressure and treated with indomethacin. Similarly, NKA partially inhibited the VIP-stimulated bicarbonate secretion. Luminal lidocaine did not affect the secretory response to NKA. The motility induced by NKA was unaffected by VIP or lidocaine but decreased by elevated intraluminal pressure. It is concluded that the NKA-induced increase in duodenal mucosal bicarbonate secretion is independent of neurons and possibly mediated by prostanoids. The increase in mucosal permeability in response to NKA may be suppressed by mucosal nerves, perhaps utilizing VIP as one of the transmitters.

[Comparison of 51Cr-EDTA with 99m-Tc-DTPA slope clearance for estimation of glomerular filtration rate using the one compartment model]

AIM

Of this study is to determine the relationship between 51Cr-EDTA and 99mTc-DTPA slope clearance applying the "one-compartment model".

METHODS

The "one-compartment model" was chosen to calculate and to compare the glomerular filtration rates of 25 patients with normal and pathological creatinin values after injection of 51Cr-EDTA and 99mTc-DTPA simultaneously.

RESULTS

The two clearance values correlated well (r = 0.996), and the 99mTc-DTPA clearance was systematically higher (28%). The 99mTc-DTPA was calculated and compared after taking three plasma samples. Taking two samples, only minor differences were seen and the correlation was high (r = 0.992).

CONCLUSION

The results of this study encouraged us to adopt the use of 99mTc-DTPA instead of 51Cr-EDTA in determining the glomerular filtration applying the "one-compartment model" in slope with two plasma samples.

Disruption of intestinal barrier function associated with experimental colitis: possible role of mast cells

The objective was to characterize changes in barrier and transport function in an experimental model of colitis, and to determine whether mast cells contribute to these changes. Colitis was induced in rats with intracolonic 2,4,6-trinitrobenzenesulfonic acid (TNBS, 30 mg) in 50% ethanol. Controls received 0.9% saline or the ethanol vehicle alone. In vivo loop perfusion was used to assess colonic water flux (in microliter.cm-1.h-1) and lumen-to-blood 51Cr-labeled EDTA clearance (% administered dose) after TNBS. Myeloperoxidase (MPO) was used as an index of granulocyte influx. TNBS or its vehicle caused a marked decrease in water absorption and an increase in permeability at 4 h after administration compared with saline. Neither dexamethasone (anti-inflammatory control) nor doxantrazole (mast cell stabilizer) was able to attenuate these early changes likely caused by the vehicle. In contrast, at later times, TNBS (but not its vehicle) also increased 51Cr-EDTA permeability and decreased water absorption; both effects were significantly attenuated by dexamethasone or doxantrazole. These drugs also significantly reduced TNBS-induced MPO accumulation and release of rat mast cell protease II. We conclude that experimental colitis is associated with severe defects in intestinal transport and barrier functions and that mast cells may contribute to the pathogenesis of these changes.

Interstitial exclusion of macromolecules studied by graded centrifugation of rat tail tendon

Mechanical compression of cartilage and tendon has been shown to expel fluid both from collagen fibrils and from the extrafibrillar space. As reported previously, albumin (Alb) concentration and colloid osmotic pressure in tendon fluid (TF) expelled by repeated centrifugations fell progressively at increasing centrifugation force (G = 600, 2,400, and 13,100), suggesting either molecular sieving in compressed tendon or mobilization of protein-free (excluded) fluid. The present experiments, including analysis of 51Cr-EDTA, aprotinin (Ap), Alb, immunoglobulin G (IgG), and hyaluronan (hyaluronic acid; HA) with molecular weight (MW) ranging from 341 to 5 x 10(6), strongly favored the exclusion hypothesis; the fraction of Alb, IgG, and HA-free fluid (excluded) was already 0.23-0.36 in the first centrifugate, increasing to 0.73-0.82 in the third. The corresponding numbers were, respectively, 0.11 and 0.43 for Ap (MW 6,500), and 0 and 0.08 for 51Cr-EDTA. These data, combined with calculated exclusion by collagen fibrils, proteoglycans, and HA, indicated that the first centrifugate was mainly derived from the extrafibrillar space, with increasing addition of macromolecular free intrafibrillar fluid in the second and third centrifugates, with each space contributing about equally to the total centrifugate volume. The calculations also indicated that Alb-, IgG-, and Ap-free fluid was mobilized from extrafibrillar space by increasing overlap of excluded territories. An excess of HA in tendon compared with that estimated from centrifugate concentrations suggests a large bound or immobilized HA fraction.

Role of neutrophils and mast cells in acute indomethacin-induced small bowel injury in the rat

The aim of this study was to determine whether the injury to the rat jejunum during the first 4.5 h exposure to indomethacin is due to an influx of neutrophils or degranulation of resident mast cells. Indomethacin and vehicle both caused changes in villous morphology (length, width, etc.) while only indomethacin injured the small bowel, as indicated by increased histological lesion score and 51Cr-ethylene diamine tetraacetate (EDTA) flux across the intestinal epithelium. Immunohistochemical staining showed the same small increase in neutrophil density (predominantly in the submucosa) following exposure to vehicle as following exposure to indomethacin. Chronic oral administration of indomethacin for 48 h did cause increased tissue neutrophil density compared to that in vehicle-fed controls. Mast cell depletion (using dexamethasone) did not alter either the indomethacin-induced increase in 51Cr-EDTA clearance or the increase in neutrophil density caused by the vehicle and by indomethacin. However, the lesion score following exposure to indomethacin was significantly lower in mast-cell-depleted animals than in control animals. We conclude that the acute phase of indomethacin-induced intestinal injury is not associated with neutrophil influx. Increased neutrophils seen after chronic indomethacin may result from injury rather than be causative. Mast cells appear to exacerbate the initial stages of indomethacin-induced intestinal injury.