Circadian rhythms of melatonin release from chicken pineal in vitro: modified melatonin radioimmunoassay

Proc Soc Exp Biol Med. 1991 Dec;198(3):826-32. doi: 10.3181/00379727-198-43320.

Abstract

An improved and simplified radioimmunoassay for measuring pineal, serum, and in vitro cultured medium melatonin is described. Using 2-[125I]iodomelatonin as radiolabeled ligand and a polyclonal rabbit antimelatonin antiserum, melatonin concentrations were determined in all three types of samples by a 2-day direct equilibrium double-antibody assay method without prior extraction. Serial dilutions of pineal homogenates, serum, and cultured medium all gave parallel displacement curves. Cross-reactivity of the antisera with other indoles was negligible. Intraassay coefficients of variation (n = 3) were 5.09, 3.32, and 5.05% at 7.81, 62.5, and 500 pg/tube, respectively, and the interassay coefficients of variation (n = 20) were 12.18% at 62.5 pg/tube. A characteristic diurnal rhythm of melatonin was observed using this direct assay for measuring daytime and nighttime chicken pineal and serum samples. An in vitro incubation of chicken pineal glands with a lighting cycle of 12-hr light:12-hr dark showed that the diurnal rhythm of melatonin secretion into the cultured medium was maintained. The direct assay method described in this report for measuring chicken melatonin using 2-[125I]iodomelatonin as radiolabeled ligand coupled with the in vitro cultured chicken pineal gland clearly offers great potential for studying the chicken pineal circadian oscillator and its underlying mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arylamine N-Acetyltransferase / analysis
  • Chickens
  • Circadian Rhythm*
  • Melatonin / analysis*
  • Melatonin / metabolism
  • Organ Culture Techniques
  • Pineal Gland / metabolism*
  • Radioimmunoassay

Substances

  • Arylamine N-Acetyltransferase
  • Melatonin