Radioimmunoassay of rat leptin: Sexual dimorphism reversed from humans

Michael Landt, Ronald L. Gingerich, Peter J Havel, Wendy M. Mueller, Bridgette Schoner, John E. Hale, Mark L. Heiman

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90 Scopus citations

Abstract

Adipose tissue secretes leptin, which interacts with receptors in the hypothalamus. In rodent models of obesity, leptin increases metabolism and decreases food intake, which helps to maintain normal body composition. Accurate and precise methods to quantitate circulating leptin concentrations are needed for physiological studies. We developed an RIA to measure leptin in rat plasma, serum, or adipocyte culture fluids. The working range of the assay, defined by the detection limit and the highest calibrator, was 0.5-50 μg/L. Recovery of 1.6-11.6 μg/L leptin added to serum was 92-103%. The rat leptin RIA correlated well with a previously developed mouse RIA when rat plasma was assayed with both methods (r = 0.94), but the mouse leptin assay underestimated rat leptin in plasma. Within- and between-run CVs were 2.4% to 5.7%. Plasma leptin concentrations correlated directly with percentage of body fat, and correlation improved when the results were separated by gender (r = 0.796, P < 0.001 for males; r = 0.710, P < 0.001 for females). Leptin concentrations were generally higher in male rats than in females; plasma leptin increased 0.60 μg/L for each percentage of increase in body fat for males but only 0.22 μg/L for females. We conclude that rat serum/plasma leptin concentrations are accurately and precisely measured with this new RIA.

Original languageEnglish (US)
Pages (from-to)565-570
Number of pages6
JournalClinical Chemistry
Volume44
Issue number3
StatePublished - 1998

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ASJC Scopus subject areas

  • Clinical Biochemistry

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Landt, M., Gingerich, R. L., Havel, P. J., Mueller, W. M., Schoner, B., Hale, J. E., & Heiman, M. L. (1998). Radioimmunoassay of rat leptin: Sexual dimorphism reversed from humans. Clinical Chemistry, 44(3), 565-570.