title: An inexpensive microcomputer digital imaging system for densitometry: quantitative autoradiography of insulin receptors with 125I and LKB Ultrofilm.
abstract: This article describes a video digitizing system designed for measuring film optical density. The system, which is based on a 6-bit (64 gray level) digitizer, solid state video camera, and Apple II microcomputer, digitizes a rectangular area selected by the operator and converts the gray level values into preselected standard units. In order to develop autoradiographic standard curves for quantitative autoradiography with 125I-insulin, liver slices labeled with 125I-insulin and plastic sections containing known amounts of tritium were apposed to the same sheet of LKB Ultrofilm for exposures of 1-7 days. The results indicate that 3H plastic standards can be used to calibrate QAR of 125I-labeled ligands with LKB Ultrofilm. The Apple system was also used to measure binding of 125I-insulin to the external plexiform layer (EPL) in slices of the rat olfactory bulb. Results suggest that the EPL has two binding sites for insulin, a high affinity site with Kd = 1.0 X 10(-8) M and a low affinity site having a Kd = 1.4 X 10(-5) M.
mesh_terms: D000818:Animals; D001345:Autoradiography / Q000295:instrumentation* / Q000379:methods; D001921:Brain / Q000378:metabolism; D003201:Computers; D003720:Densitometry / Q000295:instrumentation*; D005260:Female; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism; D008838:Microcomputers; D009830:Olfactory Bulb / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D012984:Software
chemical_list: D007457:Iodine Radioisotopes; D011972:Receptor, Insulin