Melatonin receptors in the human fetal kidney:: 2-[125I]iodomelatonin binding sites correlated with expression of Mel1a and Mel1b receptor genes

Melatonin receptors in the human fetal kidney were identified and characterized by quantitative in vitro autoradiography using the melatonin agonist, 2-[I-125]iodomelatonin. Specific binding was localized to cells in the nephrogenic region at the outer perimeter of the developing kidney and was time-dependent, saturable and inhibited in the presence of guanosine 5'-O-(3-thiotriphosphate) indicative of a G protein-coupled receptor. Expression of the Mel1a and Mel1b melatonin receptors in human fetal kidney was determined using RT-PCR. In situ hybridization confirmed the localization of the Mel1a mRNA transcripts. A role for melatonin in development of the human fetal kidney is postulated.