Surfactant protein B labelled with [(99m)Tc(CO)3(H20)3](+) retains biological activity in vitro..
Labelling of the hydrophobic surfactant protein B (SP-B) under non-reducing conditions was achieved with [(99m)Tc(CO)(3)(H2O)(3)](+) prepared according to Alberto et al. (JACS, 1998). The binding of radioactivity was protein-specific, with an overall radiochemical yield of 50%. Gel electrophoresis and Westernblot analyses showed no structural changes of SP-B. Spreading properties and surface activity of (99m)Tc-labelled SP-B in an air/water interface coincided with those of unlabelled SP-B. (99m)Tc-SP-B seems to be a promising agent to observe surfactant spreading under clinical conditions.


BACKGROUND
Therapeutic results for surfactant instillation in clinical trials are conflicting. The (99m)Tc-labelling of surfactant would allow to observe its spreading in the lung under clinical conditions.


METHODS
[(99m)Tc(CO)(3)(H2O)(3)](+) was prepared as described by Alberto et al. (JACS, 1998). This carbonyl complex was used for the direct labelling of surfactant protein B (SP-B) under non-reductive conditions by direct incubation with SP-B at elevated temperature followed by extraction into CHCl(3)/MeOH.


RESULTS
The hydrophobic protein SP-B was labelled with [(99m)Tc(CO)(3)(H2O)(3)](+). An overall radiochemical yield of about 50% was achieved. HPLC-analysis revealed a single radiolabelled species according to UV elution profile of SP-B, supported by paper and size exclusion chromatography. Gel electrophoresis confirmed that the dimer structure of SP-B was preserved. Spreading properties of (99m)Tc-labelled SP-B in an air/water interface coincided with those of unlabelled SP-B. Spreading of radioactivity observed in a glass trough of 26 cm x 27 cm with a gamma camera was completed during the first 7-9 sec after application of (99m)Tc-labelled SP-B. The corresponding decrease of surface tension to 45 mN/m at the peripheral surface tension sensors took 7 sec +/- 2 sec (MEAN +/- STD; n = 3).


CONCLUSIONS
Direct and specific (99m)Tc-labelling of the hydrophobic surfactant protein B was achieved using the [(99m)Tc(CO)(3)(H2O)(3)](+) precursor. This procedure can easily be used to prepare specifically labelled surfactant mixtures with spreading properties that coincide with those of unlabelled surfactant.
Amann
A
A
Department of Anesthesiology and Critical Care Medicine, Leopold-Franzens-University of Innsbruck, Innsbruck, Austria. anton.amann@uibk.ac.at
Decristoforo
C
C
Ott
I
I
Wenger
M
M
Bader
D
D
Alberto
R
R
Putz
G
G
D000818:Animals; D001345:Autoradiography; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D008168:Lung / Q000000981:diagnostic imaging*; D011498:Protein Precursors / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology; D011510:Proteolipids / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000737:chemistry; D017556:Technetium Compounds / Q000737:chemistry
D011498:Protein Precursors; D011510:Proteolipids; D019275:Radiopharmaceuticals; D017556:Technetium Compounds; C105511:surfactant protein B propeptide