A solid-phase radioimmunoassay for detection of insulin synthesized by islet cell clones is described. This assay employs anti-insulin antibody adsorbed onto fenestrated polyvinyl chloride 96-well plates ('transfer plates'). The calibrated aperture in the bottom of each transfer plate well permits fluid to enter the wells when transfer plates are lowered into microculture wells containing insulin. With this assay it is possible to rapidly screen hundreds of islet cell cultures for insulin production. We have used this assay to facilitate cloning of the RIN rat insulinoma cell line. The assay readily detects insulin synthesis by RIN cells and [125I]insulin is not displaced by culture medium from cells which do not produce insulin. The transfer plate format should be applicable to semiautomate other radioimmunoassays.
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