Growth factors, radiolabeled

Bioassays of related substances can be quite similar in design. Specific growth factors, for example, stimulate the accelerated growth of specific animal cell lines. Relevant bioassays can be undertaken by incubation of the growth-factor-containing sample with a culture of the relevant sensitive cells and radiolabelled nucleotide precursors. After an appropriate time period, the level of radioactivity incorporated into the DNA of the cells is measured. This is a measure of the bioactivity of the growth factor. 

Fig. 20. In vitro cumulative release of radiolabeled fibroblast growth factor (bFGF) in PBS at 22 °C and 37 °C. Nanoparticle chemistry was same as in Fig. 3, except 0.00215 % bFGF was added in place of CC. The amount of bFGF captured (EE) was 7 %. This number also includes losses in the labeling process, as well. Concentration of nanoparticles was approximately 2.5 mg per batch (volume 0.5 mL)...

Blankenberg FG, Mandl S, Cao YA et al (2004) Tumor imaging using a standardized radiolabelled adapter protein docked to vascular endothelial growth factor. J Nucl Med 45 1373-1380 Blum JE, Handmaker H, Rinne NA (1999) The utility of a somatostatin-type receptor binding peptide radiopharmaceutical (P829) in the evaluation of solitary pulmonary nodules. Chest... 

Capala J, Barth RF, Bailey MQ et al (1997) Radiolabelling of epidermal growth factor with Tc and in vivo localization following intracerebral injection into normal and glioma-bearing rats. Bioconjug Chem 8 289-295... 

A number of cyclic polyols also are known to occur (Fig. 15.13). myo-Inositol (62), widespread in animals, is a growth factor in yeasts and a group B vitamin. This compound, one of nine possible stereoisomers, is widespread in plants (six other isomers also are naturally occurring). When plant cells are incubated with radiolabeled myo-inositol, a large portion of the label appears in the pentose and uronic acid residues of the cell wall (Karr, 1976 Loewus and Loewus, 1980). myo-Inositol serves as a precursor for o-glucuronic acid (3). Furthermore, when glucose and other monosaccharides are incorporated into cell walls, myo-inositol appears to be an intermediate (Karr, 1976 Loewus and Loewus, 1980). Analytical techniques for the study of cyclitols and sugar alcohols (polyols) have been reviewed (Beck and Hopf, 1990 Loewus, 1990). 

Selection of a bloassay depends on the growth parameters to be measured and the quantity of allelochemlcal available. For example, the sorghum seedling bloassay used In our studies may be the best for determining the uptake, distribution, and metabolism of known allelochemlcals where quantity of compound Is not a factor and the use of radiolabeled materials would be expedient. 

---