Melanophores/metabolism; Melatonin/pharmacology; Receptors, Cell Surface/biosynthesis; Skin/metabolism; Amino Acid Sequence; Animals; CHO Cells; Cell Line; Cell Membrane/metabolism; Cells, Cultured; Chlorocebus aethiops; Cloning, Molecular; Colforsin/pharmacology; Cricetinae; Cyclic AMP/metabolism; DNA/chemistry; DNA/metabolism; DNA, Complementary/isolation & purification; DNA, Complementary/metabolism; Gene Expression; Kidney; Kinetics; Molecular Sequence Data; Poly A/analysis; Poly A/biosynthesis; Protein Structure, Secondary; RNA/analysis; RNA/biosynthesis; RNA, Messenger; Receptors, Cell Surface/chemistry; Receptors, Cell Surface/metabolism; Receptors, Melatonin; Transcription, Genetic; Transfection; Xenopus laevis