99mTc-albumin can replace 125I-albumin to determine plasma volume repeatedly.

OBJECTIVE: Plasma volume assessment may be of importance in several disorders. The purpose of the present study was to compare the reliability of plasma volume measurements by technetium-labeled human serum albumin ((99m)Tc-HSA) with a simultaneously performed plasma volume determination with iodine-labeled human serum albumin ((125)I-HSA). MATERIALS AND METHODS: In 15 healthy volunteers, simultaneous plasma volume measurements with (99m)Tc-HSA and (125)I-HSA were performed after ½ hour in the supine position. Blood samples were obtained 10, 15, 20, and 30 minutes after the injection for accurate retropolation from the plasma counts to time zero to correct for leakage of the isotopes from the circulation. RESULTS: The mean difference (bias) between plasma volume measured with (125)I-albumin and (99m)Tc-albumin was 8 ml (0.1 ml/kg) with limits of agreement (bias ±1.96 SD) ranging from -181-196 ml (-2.3-2.5 ml/kg). The tracer disappearance rate was significantly higher with (99m)Tc-albumin (-23.1±7.1%/h) than with (125)I-albumin (-6.7±3.6%/h) (p <0.001). CONCLUSION: This study demonstrates that (99m)Tc-HSA can replace (125)I-HSA for single measurements of plasma volume in healthy volunteers. It needs to be emphasized however, that repeated blood sampling for 1/2 hour after injection of the tracer is required to correct for the disappearance of (99m)Tc and (99m)Tc-HSA from the circulation.

Technetium-99m-labeled autologous serum albumin: a personal-exclusive source of serum component.

Technetium-99m human serum albumin ((99m)Tc-HSA) is an important radiopharmaceutical required in nuclear medicine studies. However, the risk of transfusion-transmitted infection remains a major safety concern. Autopreparation of serum component acquired from patient provides a "personal-exclusive" source for radiolabeling. This paper is to evaluate the practicality of on-site elusion and subsequent radiolabeling efficacy for serum albumin. Results showed that the autologous elute contained more albumin fraction than serum without extraction procedure. Good radiochemical purity and stability were demonstrated after radiolabeling. Biodistribution study showed that labeled albumin accumulated immediately in the lung, liver, and kidney. It was cleared steadily and excreted in the urine. The biologic half-life was defined, and all samples passed the pyrogenicity and sterility tests. In conclusion, autoalbumin could be extracted and radiolabeled properly in a nuclear medicine setting. Moreover, the risk of transfusion-transmitted infection associated with nonautologous, multisource (99m)Tc-HSA agents can be reduced.

Technetium-99m-GSA clearance in mice under long-term dietary restriction.

OBJECTIVE: Dietary restriction (DR) without malnutrition is widely acknowledged to prolong lifespan in laboratory animals. Evidence suggests that DR retards age-related decline in protein turnover of most organs. However, there has been no report about hepatic serum glycoprotein catabolism under DR. In the current study, we evaluate the hepatic uptake of asialoglycoprotein in ICR mice with DR by measuring the plasma clearance of technetium-99m galactosyl human serum albumin (Tc-GSA). METHODS: The amount of food supplied to the restricted mice was 70% of that consumed by the mice fed ad libitum (AL). The regimen was initiated at the age of 7 weeks and terminated after the age of 44 weeks. The plasma clearance of Tc-GSA was measured at the age of 7 weeks, 14 weeks, 28 weeks, and 42 weeks. RESULTS: The restricted animals showed a marked decrease in their body and liver weight, and hepatic uptake of Tc-GSA per liver weight in the restricted mice was greater than that in the mice fed AL. On the other hand, the Tc-GSA plasma clearance in the mice fed AL was stable during the study period, and that in the restricted mice showed no change with age either, and those in the two groups were similar. In addition to the receptor function, there was no difference in the expression of mRNAs of the asialoglycoprotein receptor between the two groups. Serum concentrations of cholinesterase and hepatic mRNAs of glutamine synthetase in the restricted mice were higher than those in the mice fed AL. Serum levels of amino acids in the restricted mice were lower than those in the mice fed AL. CONCLUSIONS: The data presented here show that the DR did not affect the capacity of hepatic serum glycoprotein catabolism, whereas several protein metabolic pathways were affected.

Neuregulin-1-beta1 enters brain and spinal cord by receptor-mediated transport.

Proteins of the neuregulin (NRG) family play important regulatory roles in neuronal survival and synaptic activity. NRG-1-beta1 has particular potential as a therapeutic agent because it enhances myelination of neurites in spinal cord explants. In this study, we determined the permeation of NRG-1-beta1 across the blood-brain and blood-spinal cord barriers (BBB and BSCB respectively). Intact radioactively labeled NRG-1-beta1 had a saturable and relatively rapid influx rate from blood to the CNS in mice. Capillary depletion studies showed that NRG-1-beta1 entered the parenchyma of the brain and spinal cord rather than being trapped in the capillaries that compose the BBB. The possible mechanism of receptor-mediated transport was shown by the ability of antibodies to erbB3 and erbB4 receptors to inhibit the influx. Lipophilicity, less important for such saturable transport mechanisms, was measured by the octanol : buffer partition coefficient and found to be low. The results indicate that NRG-1-beta1 enters spinal cord and brain by a saturable receptor-mediated mechanism, which provides the opportunity for possible therapeutic manipulation at the BBB level.

Ballistic CTLA4 and IL-4 gene transfer into the lower lid prolongs orthotopic corneal graft survival in mice.

PURPOSE: To explore outflow from the eye and to determine and modulate the influence of lymphatic drainage on corneal graft survival in mice. METHODS: Tracer experiments were conducted in BALB/c mice using the (99m)Tc colloidal albumin Nanocoll. Count rates were determined in the eyes, submandibular lymph nodes, spleen, liver and blood 24 h after subconjunctival, intracorneal, intracameral (anterior chamber), intravenous and subcutaneous lower-lid or upper-lid injections ( n=6 each). Four groups of BALB/c mice ( n=8) received corneal transplants from C3H mice; two of them were treated ballistically with vector CTLA4+IL-4 onto the leg or the lower lid, one group was untreated and the other control group was treated with an empty minimalistic, immunologically defined, gene expression (MIDGE) vector. RESULTS: Radioactivity was detected in the liver, spleen and ipsilateral submandibular lymph node after intracameral injection as follows: 91.9%, 6.6% and 1.2% respectively. Radioactivity uptake of the ipsilateral submandibular lymph node was also low after intravenous injection (0.1%) but high after intracorneal (33.8%), lower-lid (62.0%) and subconjunctival (71.2%) injection. Vector CTLA4+IL-4 treatment of the lower lid but not of the leg prolonged graft survival ( P=0.004). CONCLUSION: These tracer studies confirmed for the first time identical lymphatic drainage from the cornea and the lower lid. Logically, lymphatic drainage could be manipulated and graft survival improved by gene transfer to the lower lid.

Circulating TGF-beta1 does not cross the intact blood-brain barrier.

Transforming growth factor-beta (TGF-beta) from the periphery can cross the disrupted blood-brain barrier (BBB) to exert neuroprotective effects on the brain. Here, we quantify its permeation across the normal mouse BBB. By high-performance liquid chromatography, we show that TGF-beta1 is stable in circulating blood but does not cross the intact BBB after intravenous injection any faster than the vascular marker 99mTc-albumin. This poor rate of influx cannot be explained by rapid efflux out of the brain or lack of lipophilicity as measured by the octanol/buffer partition coefficient, although the hydrogen bonding potential was relatively high, consistent with poor penetration. Thus, the therapeutic potential of TGF-beta1 administered in blood is probably limited to situations in which the BBB has been disrupted.

Clinical assessment of hepatic functional reserve using 99mTc DTPA galactosyl human serum albumin SPECT to prognosticate chronic hepatic diseases--validation of the use of SPECT and a new indicator.

RATIONALE: It is generally known that scintigraphy of 99mTc diethylenetriamine pentaacetic acid-galactosyl human serum albumin (99mTc-GSA) is useful for assessing hepatic functional reserve. For hepatic functional indicators, the index of the calculated planar image has been used in previous studies. However, there have been few reports that suggest that the indicators calculated from static SPECT data would be useful for the assessment of hepatic function. The aims of this study were to establish a simple method for assessing hepatic functional reserve using the liver SPECT of 99mTc-GSA and to apply this method for rich stratification in patients with chronic hepatic diseases. METHODS: A liver phantom (a 50% concentration of 99mTc solution) was used to compare the planar and SPECT methods. According to the definition of the new indicator, the liver SPECT of 99mTc-GSA was divided by a syringe SPECT of 99mTc-GSA and was called the liver uptake ratio (LUR). We correlated the LUR and the liver uptake ratio calculated according to the blood-sampling method. 99mTc-GSA SPECT was performed in 137 patients with hepatic diseases, including chronic hepatic diseases, and 20 healthy volunteers. The LUR was correlated between the formed subtypes for all subjects. RESULTS: The acquired phantom-count ratio calculated by the SPECT method was more accurate than that acquired by the planar method. A good correlation was obtained between the LUR and the blood-sampling method (r = 0.971). The LUR was significantly lower in subjects with severe cirrhosis than in healthy subjects or those with chronic hepatitis and mild cirrhosis, and it was significantly lower in subjects with chronic hepatitis and mild cirrhosis than in healthy subjects. The LUR was significantly correlated with other hepatic function tests. Based on LUR, the chronic hepatic diseases were divided into two groups: Group A, with LURs 30% and higher, and Group B, with LURs below 30%. An LUR of 30% marked the 25th percentile of the mild-cirrhosis group. The cumulative survival rates were lower in Group B than in Group A. CONCLUSION: The SPECT method was superior to the planar method for assessing LURs. LUR was a suitable indicator of 99mTc-GSA clearance from the blood pool and of binding to the asialo-glycoprotein receptor. LUR is a simple and clinically useful indicator for the assessment of hepatic functional reserve in chronic hepatic diseases.

Estimation of fractional liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin: an application of a simple graphical method to dynamic SPECT.

The objective of this study was to investigate clinical utility of a graphical method for estimating liver uptake and blood retention of 99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA; DTPA is diethylenetriaminepentaacetic acid) using dynamic single photon emission computed tomography (SPECT) data. When considering the kinetics of 99mTc-GSA, if it is assumed that (1) 99mTc-GSA distributes only between blood and liver, and (2) no metabolism of 99mTc-GSA occurs during the observation period, a plot of liver counts versus cardiac blood pool counts should, theoretically, be a straight line. From the slope and y intercept of a regression line, coefficients for converting count based liver and blood pool data to the per cent injected dose (%ID) can be calculated. The applicability of this method was tested on dynamic SPECT data from 30 patients with liver dysfunction. To validate this method, plasma concentrations (%ID/ml plasma) at 6, 15 and 30 min after the injection were estimated by this method and compared with the measured ones. To investigate the clinical significance of the per cent liver uptake, the value obtained by this method was compared with the results of conventional liver function tests, including serum albumin, the hepaplastin test, prothrombin time and indocyanine green clearance. In every data set, a plot of liver counts to cardiac blood pool counts was fitted well by a straight line (P<0.00001). Estimated plasma concentrations by this method showed good correlation with the measured ones at 6, 15 and 30 min after the injection (r=0.748, 0.838, 0.875, respectively; P<0.0001). The liver uptake determined by this method showed good correlation with the results of conventional hepatic function tests (P<0.002). The graphical method could provide an accurate estimate of %ID of 99mTc-GSA in blood without the need for blood sampling. The liver uptake determined by this method could be a simple but useful quantitative indicator of hepatic function.

Mechanism of accumulation of 99mTc-sulesomab in inflammation.

UNLABELLED: 99mTc-Sulesomab, the Fab fragment of anti-NCA-90, is used as an in vivo granulocyte labeling agent for imaging inflammation. It is not clear to what extent it targets cells that have already migrated into the interstitial space of an inflammatory lesion as opposed to circulating cells. The contribution to signal of radioprotein diffusion in the setting of increased vascular permeability is also poorly documented. METHODS: We compared the local kinetics of (99m)Tc-sulesomab and (99m)Tc-labeled human serum albumin (HSA), which have similar molecular sizes, in 7 patients with orthopedic infection proven by clearly positive (111)In-leukocyte scintigraphy. (99m)Tc-Sulesomab and (99m)Tc-HSA were administered in sequence separated by an interval of 2-6 d. Images were obtained 1, 3, 4, and 6 h after injection, and multiple venous blood samples were obtained for blood clearance measurement. Patlak-Rutland (P-R) analysis was performed to measure lesion and control tissue protein clearance. Target-to-background tissue (T/Bkg) ratios were calculated for each radioprotein and compared with the T/Bkg ratio for (111)In-leukocytes. (99m)Tc-Sulesomab binding to granulocytes was measured in vitro and ex vivo and to primed and activated granulocytes in vitro. RESULTS: After intravenous injection, <5% of the circulating radioactivity was cell bound with both radioproteins so that the P-R curves could therefore be assumed to represent extravascular uptake of free protein. The blood clearance (mean +/- SD) of sulesomab was 23.4 +/- 11.7 mL/min, approximately 5 times greater than that of HSA, for which it was 4.8 +/- 3.1 mL/min. Likewise, clearance into the lesion of sulesomab was consistently higher than that of HSA, on average about 3 times as high. Nevertheless, the T/Bkg ratios for sulesomab and HSA were similar, except at 6 h when that of HSA (2.14 +/- 0.6) was higher than that of sulesomab (1.93 +/- 0.5; P approximately 0.01). Both values were considerably less than the T/Bkg ratio on the (111)In-leukocyte images, which, at 22 h, was 12.3 +/- 5.3. Moderate clearance of sulesomab, but not HSA, was seen in the control tissue. Granulocytes bound significantly more (99m)Tc-sulesomab in vitro when primed or activated. CONCLUSION: (a) Sulesomab does not localize in inflammation as a result of binding to circulating granulocytes; (b) sulesomab is cleared into inflammation nonspecifically via increased vascular permeability; nevertheless, it may be cleared after local binding to primed granulocytes or bind to activated, migrated extravascular granulocytes; and (c) HSA produces a similar or higher T/Bkg ratio than sulesomab because sulesomab is cleared into normal tissues and because image positivity in inflammation is significantly dependent on local blood-pool expansion.

Passage of intratracheally instilled ultrafine particles from the lung into the systemic circulation in hamster.

The mechanisms of particulate pollution-related cardiovascular morbidity and mortality are not well understood. We studied the passage of radioactively labeled ultrafine particles after their intratracheal instillation. Hamsters received a single intratracheal instillation of 100 microg albumin nanocolloid particles (nominal diameter < or = 80 nm) labeled with 100 microCi technetium-99m and were killed after 5, 15, 30, and 60 min. In blood, radioactivity, expressed as percentage of total body radioactivity per gram blood, amounted to 2.88 +/- 0.80%, 1.30 +/- 0.17%, 1.52 +/- 0.46%, and 0.21 +/- 0.06% at 5, 15, 30, and 60 min, respectively. Thin-layer chromatography showed only one peak of radioactivity corresponding to unaltered (99m)Tc-albumin nanocolloid. In the liver, radioactivity, expressed as percentage of total radioactivity per organ, amounted to 0.10 +/- 0.07%, 0.23 +/- 0.06%, 1.24 +/- 0.27%, and 0.06 +/- 0.02% at 5, 15, 30, and 60 min, respectively. Lower values were observed in the heart, spleen, kidneys, and brain. Dose dependence was assessed at 30 min following instillation of 10 microg and 1 microg (99m)Tc-albumin per animal (n = 3 at each dose), and values of the same relative magnitudes as after instillation of 100 microg were obtained. We conclude that a significant fraction of (99m)Tc-albumin, taken as a model of ultrafine particles, rapidly diffuses from the lungs into the systemic circulation.

[Calcium channel blocking agents and albuminuria in diabetic and hypertensive patients. A pilot study]. / Agents bloqueurs des canaux calciques et albuminurie des sujets diabétiques et hypertendus. Une étude pilote.

UNLABELLED: Diltiazem tends to decrease proteinuria in hypertensive diabetic subjects in comparison to amlodipine that does not modify it. Since estimated glomerular pressure is identical in amlodipine treated and diltiazem treated subjects, differences in albuminuria may be explained by different renal tubular reabsorption rates. OBJECTIVES: To compare plasma clearances (PC) of technetium labeled albumin (albumin-Tc99m) obtained by serial plasma measurements with PC obtained by urinary excretion measurements. Indirectly evaluate tubular reabsorption of albumin-Tc99m. Test the hypothesis that amlodipine decreases renal tubular reabsorption of albumin in diabetic hypertensive subjects. METHODS: Fourteen diabetic and hypertensive subjects (DH) (average plasma creatinine: 94 mmol/L) and 6 normal subjects (average plasma creatinine: 82 mmol/L) had previously been assessed for albumin-Tc99m PC. Eleven of these 14 DH subjects were then randomized to diltiazem 300 mg/daily (6 subjects) or amlodipine 10 mg/daily (5 subjects). Their glomerular filtration, glomerular pressure and albumin-Tc99m PC were then assessed on the 3rd, 6th, and 12th month of the study. RESULTS: Albumin-Tc99m PC obtained from serial blood draws: A decrease in PC between months 0 and 3 from 14 to 10.6 cc/min was observed in subjects treated with amlodipine but subjects on diltiazem showed PC stability (from 11.9 to 12 cm3/min). PC obtained from urinary excretion: Amlodipine and diltiazem treated subjects showed PC stability. Plasma volume in amlodipine treated subjects decreased from 156 to 127% and diltiazem treated subjects from 128 to 117%. CONCLUSION: A decrease in PC obtained with plasma measurements and stability of PC based on urinary excretion measurements tends to identify a decrease in plasma volume. A decrease in albumin-Tc99m tubular reabsorption was not observed. The estimate of albumin PC with Tc 99m labelled albumin measurements still needs to be validated.

Assessment of liver function in chronic liver diseases and regional function of irradiated liver by means of 99mTc-galactosyl-human serum albumin liver scintigraphy and quantitative spectral analysis.

Scintigraphy with 99mTc-diethylenetriamine pentaacetic acid galactosyl human serum albumin (99mTc-GSA) was performed on 102 patients, then the hepatic extraction fraction (HEF), the rate constant for liver uptake of the tracer from the blood (K1) and the hepatic blood flow index (HBFI) were determined by spectral analysis. The HEF, K1 and HBFI values correlated moderately or closely with various indices of hepatic function, and the HEF and K1 values decreased according to the stage of liver dysfunction. The HEF and K1 values linearly and nonlinearly correlated with HH15 and LHL15, respectively. The HEF, K1 and HBFI values for the irradiated portion of 20 patients before and alter irradiation were compared. The HEF value in patients with a cirrhotic liver significantly (p < 0.002) decreased compared with that in patients with a normal liver at a dose of less than 40 Gy, whereas the HBFI value in patients with a normal liver significantly (p < 0.05) decreased compared with that in patients with a cirrhotic liver at a dose of 40 Gy or greater. This method appears to be a simple, non-invasive and useful tool with which to quantitatively evaluate liver function and it also helps clarify changes in regional function of the irradiated liver.

Nontumorous decrease in Tc-99m GSA accumulation.

Nontutimorous decrease in 99mTc-GSA accumulation has not been well covered in the literature. Understanding of this phenomenon is, however, essential for accurate evaluation of regional hepatic function. Scintigrams (transaxial SPECT) of 269 patients who underwent 99mTc-GSA liver scintigraphy were reviewed for the presence of nontumorous decreases in 99mTc-GSA accumulation. Nontumorous decreases in 99mTc-GSA accumulation were seen in 32 of 269 patients (12%). In 16 of the 32 patients (6%), nontumorous decreases in 99mTc-GSA accumulation corresponded to regional decrease in portal venous flow. The causes of such decrease in portal venous flow were portal thrombus of hepatocellular carcinomas in eight patients, portal venous stenosis or occlusion by hilar cholangiocarcinomas in five patients, inter alia. In eight patients (3%), the regions with decreased 99mTc-GSA accumulation correlated with massive hepatic necrosis in fulminant hepatitis, scar in hepatitis, or confleuent in portal venous flow, lobar biliary stasis, or both. In four patients (1.5%), the exact causes of nontumorous decrease in 99mTc-GSA accumulation could not be determined.

Validation of curve-fitting method for blood retention of 99mTc-GSA: comparison with blood sampling method.

We investigated a curve-fitting method for the rate of blood retention of 99mTc-galactosyl serum albumin (GSA) as a substitute for the blood sampling method. Seven healthy volunteers and 27 patients with liver disease underwent 99mTc-GSA scanning. After normalization of the y-intercept as 100 percent, a biexponential regression curve for the precordial time-activity curve provided the percent injected dose (%ID) of 99mTc-GSA in the blood without blood sampling. The discrepancy between %ID obtained by the curve-fitting method and that by the multiple blood samples was minimal in normal volunteers 3.1 +/- 2.1% (mean+/-standard deviation, n = 77 sampling). Slightly greater discrepancy was observed in patients with liver disease (7.5 +/- 6.1%, n = 135 sampling). The %ID at 15 min after injection obtained from the fitted curve was significantly greater in patients with liver cirrhosis than in the controls (53.2 +/- 11.6%, n = 13; vs. 31.9 +/- 2.8%, n = 7, p < 0.0001). There was a highly linear correlation between the %IDs of 99mTc-GSA and the plasma retention rate for indocyanine green (r = -0.869, p < 0.0001, n = 27). These results indicate that the curve-fitting method provides an accurate %ID of 99mTc-GSA and could be a substitute for the blood sampling method.

[Usefulness of blood disappearance corrected hepatic uptake ratio (LHL/HH) as a hepatic functional index using 99mTc-galactosyl serum albumin].

The authors introduced blood disappearance corrected hepatic uptake ratio (LHL/HH) as an index of hepatic function using 185 MBq/3 mg of 99mTc-galactosyl serum albumin (GSA). Three ratio parameters, the hepatic uptake ratio (LHL15), blood disappearance ratio (HH15), and LHL15 divided by HH15 (LHL/HH) were evaluated with percent injected dose of 99mTc-GSA in blood at 15 min after injection (%ID15) and hepatic functional severity graded by Child-Turcotte criteria score. Seventy eight patients with chronic liver disease were studied. There was a poor linear correlation between the LHL15 and %ID15, because the LHL15 formed a plateau phase in the lower-value range for %ID15. In contrast, LHL/HH showed an excellent linear correlation with %ID15 in its whole range. In the comparison with the clinical functional severity, LHL/HH gave a more highly significant difference (p < 0.001) than LHL15 (p = 0.005) between the normal and mild dysfunction groups and gave a significant difference (p = 0.032) between the mild and moderate groups, in which HH15 showed no meaningful difference (p = 0.07). This index is obtained with no difficult procedures and can be regarded as a unified parameter for hepatic uptake and blood disappearance. It is hoped that LHL/HH will prove useful in the diagnosis of hepatic functional severity using 99mTc-GSA.

Technetium-99m labelled human serum albumin for ventriculography: a comparative evaluation of six labelling kits.

In this study we have compared the characteristics of six labelling kits for the preparation of technetium-99m labelled human serum albumin (99mTc-HSA) and evaluated the usefulness of the various 99mTc-HSA preparations as blood pool tracer agents. The amount of the principal ingredients, i.e. HSA and stannous ions, varies largely between the studied kits and this is probably a reason for the observed differences in the labelling rate. Analysis of the reaction mixtures after labelling of the respective kits with 99mTc showed in each preparation the presence of four to five radioactive components in variable relative amounts. The retention time of the main component on size-exclusion high-performance liquid chromatography (SEC-HPLC) was identical for all preparations. Biodistribution of the HPLC-isolated fractions was studied in mice. The components with the shortest and longest retention times on HPLC show poor retention in the plasma. The three intermediate fractions, including the principal peak, are initially retained relatively well in the blood (60%-70% of the injected dose after 10 min), but clearly to a lower degree than iodine-125 labelled HSA. Moreover, they diffuse out of the vascular compartment at a much higher rate than 125I-HSA. The biological behaviour of the main component of the various preparations was clearly different, despite the identical retention time on SEC-HPLC. Study of the total preparations in mice and a rabbit showed that two of them are cleared rapidly from the blood and cannot be considered valuable blood pool tracers. Diffusion of the other preparations out of the blood is slower but also considerable and compromises their use for ventriculography.