Melatonin receptor mRNA expression in human granulosa cells

We have shown that the melatonin receptor agonist, 2-[ 125I] iodomelatonin, binds to high-affinity guanine nucleotide-sensitive sites on human granulosa (HG) cell membranes. In order to confirm the presence of melatonin receptors in HG cells, we have now used a reverse transcriptase-polymerase chain reaction (RT-PCR) procedure to examine receptor subtype expression. RT-PCR studies revealed the presence of the mt 1 (Mel 1a) melatonin receptor subtype in ten single or pooled HG cell samples which were obtained from 14 patients. In contrast, expression of MT 2 ( Mel 1b) mRNA was observed in only two of these HG samples. DNA sequencing of the mt 1 PCR product confirmed its identity with the reported human mt 1 melatonin receptor. The expression of mt 1 and MT 2 receptor mRNA in HG cells and the reported presence of melatonin in human follicular fluid indicate a potentially important role for this hormone in regulating human ovarian and reproductive function.