Practical considerations in analyzing radioreceptor assays by Scatchard analysis and capacity determination in irreversible hormone receptor interactions

The Scatchard plot in a radioreceptor assay depends upon the definition of specific binding and the quality of the iodinated hormone used. Iodination of protein hormones may alter it so that it no longer binds to the receptor and methods are available to measure the extent of this inactivation. When appropriate corrections are made for specific binding and the amount of inactive iodinated hormone in an assay, both qualitative and quantitative differences were observed in estimates of binding capacity and affinity in some well characterised hormone receptor systems. Theoretical predictions derived from Scatchard analysis of irreversible unimolecular hormone-receptor interactions were applicable, both qualitatively and quantitatively to two irreversible hormone-receptor systems. A method described permits a more accurate estimate of capacity from radioreceptor assay data.