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

Abstract

Melatonin receptors in the human fetal kidney were identified and characterized by quantitative in vitro autoradiography using the melatonin agonist, 2-[ 125 I]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 -0-(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.

Melatonin Receptor Subtype MT2 (Mel 1b) and Not mt1 (Mel 1a) Is Associated with Melatonin-Induced Enhancement of Cell-Mediated and Humoral Immunity

“…In addition, melatonin receptors have been identified on a number of different immune tissues, including splenocytes, lymphocytes, thymocytes, and monocytes [16, 20, 33, 34]. Unlike the case for other peripheral tissues [35, 36], the precise melatonin receptor subtypes occupying lymphoid tissue remain to be identified. The present data, however, provide the first indirect evidence that MT2 receptors may be present on splenocytes, given that this subtype appears to be at least partially responsible for mediating melatonin-induced immune enhancement.…”

International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, Classification, and Pharmacology of G Protein-Coupled Melatonin Receptors

“…Using RT-PCR, mRNA for both types has been amplified from human fetal kidney (Drew et al, 1998), granulosa cells (Niles et al, 1999), PAZ6 adipocytes , and coronary arteries (Ekmekcioglu et al, 2001a). MT 1 melatonin receptors were localized by immunocytochemistry to both adult and fetal human kidney (Song et al, 1997;Drew et al, 1998).…”

What is the role of melatonin within the anterior pituitary?

“…In fetal and newborn animals, melatonin receptors are expressed more widely, both in the CNS and in the pituitary (Williams et al 1991, Helliwell & Williams 1994, and in other tissues in which expression is absent in the adult (e.g. the developing renal cortex (Drew et al 1998)). Physiological studies support the view that specific regions of melatonin receptor expression are responsible for mediating specific aspects of the overall response to melatonin.…”

“…Hence, one cannot simply exclude control of cell differentiation as a mode of melatonin action on temporal considerations. The second point to make is that transient expression of melatonin receptors is observed during development of tissues beyond the pituitary -for example, in the nephrogenic region of the developing human kidney around week 20 of fetal life (Drew et al 1998). Thirdly, it is worth noting that, in songbirds, seasonal control of changes in the capacity for birdsong has been linked with melatonindependent changes in the volume of central regions concerned with this function, presumably through melatonin effects on cell recruitment/turnover (Bentley et al 1999).…”