A sensitive radioimmunoassay optimized for reproducible measurement of rat plasma insulin

Journal of Pharmacological and Toxicological Methods
M C Cam, J H McNeill


There has been a notable lack of consistency in plasma insulin values reported in the literature. In an attempt to find a more reproducible and sensitive insulin radioimmunoassay (RIA) method for the measurement of plasma insulin, the charcoal adsorption method for separation of free from antibody-bound antigen was investigated. The applicability of this method towards the measurement of plasma insulin, however, has been known to be severely limited because of interference by plasma proteins with charcoal binding. Indeed, the assay resulted in negative fasting insulin values and unacceptable interassay variability, which was not improved by adding charcoal-extracted plasma (CEP) to the standard curve. In this paper, we demonstrate a process by which relatively small volumes (25 microL) of plasma from control, diabetic, and fasted rats can be assayed reproducibly with charcoal in the final separation step. It was observed that the assay of insulin-free plasma, in the form of CEP, could represent a distinct "zero insulin" level specific for plasma samples, in place of the zero insulin standard (insulin-free standard buffer) routinely used. Normalizing plasma samples against CEP resulted in lower intra-assay and interassay variabi...Continue Reading


Mar 1, 1976·Hormone and Metabolic Research = Hormon- Und Stoffwechselforschung = Hormones Et Métabolisme·K N Frayn
Jan 1, 1988·Journal of Immunoassay·H L Bank
Nov 1, 1969·The Journal of Clinical Investigation·A JunodA E Renold
Feb 1, 1973·The Journal of Clinical Endocrinology and Metabolism·M A Binoux, W D Odell
Oct 1, 1965·The Journal of Clinical Endocrinology and Metabolism·V HerbertS J Bleicher
Jul 1, 1994·Diabetes/metabolism Reviews·P M Clark, C N Hales

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