Ontogenesis of melatonin receptors in anterior pituitary and pars tuberalis of golden hamsters.

The ontogenesis of melatonin receptors in the anterior pituitary and pars tuberalis of the Golden hamster was studied using [125I]iodomelatonin as a ligand. The affinity of the binding site to the ligand (Kd) was in the range 21 to 54 pM and it did not change significantly during development. The concentration of the [125I]iodomelatonin binding sites in the anterior pituitary was highest in one-day-old hamsters (Bmax = 14 fmol/mg protein) and thereafter gradually decreased. In adults it reached to about 6% of the neonatal values. In contrast, the concentration of the binding sites in pars tuberalis did not change significantly during ontogenesis and it was in the range of 3 to 5 fmol/mg protein.