Effects of cyclic 3',5'-AMP and other adenine nucleotides on the melanophores of the lizard (Anolis carolinensis).
1. Cyclic 3',5'-AMP has been reported to darken skins of the frog, Rana pipiens. This suggests that cyclic 3',5'-AMP may mediate the action of MSH on amphibian chromatophores. Since MSH also darkens skins of the lizard, Anolis carolinensis, we investigated the effects of cyclic 3',5'-AMP and other nucleotides on Anolis melanophores to determine whether cyclic 3',5'-AMP may be the intracellular mediator of hormone action on melanophores of another vertebrate class.2. Cyclic 3',5'-AMP, itself, causes a rapid melanin granule aggregation within melanophores of Anolis. This response is, however, somewhat nonspecific in that both 5'-ATP and 5'-ADP also lighten the skins by aggregating the melanin granules. Another nucleotide, 5'-AMP, darkens the skins by dispersing melanin granules. Cyclic 2',3'-AMP does not darken or lighten Anolis skins.3. Dibutyryl cyclic 3',5'-AMP, which is considered to be better able to penetrate membranes and resist degradation by a specific phosphodiesterase, maximally darkens Anolis skins, as does MSH. This darkening by the potent dibutyryl cyclic 3',5'-AMP suggests that cyclic 3',5'-AMP may be the intracellular mediator of melanin granule dispersion within Anolis melanophores leading to skin darkening.4. Other evidence supporting the first-messenger-second-messenger hypothesis for melanophore regulation is discussed.5. The differences in responses of Anolis melanophores to adenine nucleotides may relate to the ability of these agents to penetrate melanophore membranes; thus, the nucleotides could exert their effects either intracellularly or extracellularly on the plasma membrane.
D000227:Adenine Nucleotides / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D002462:Cell Membrane / Q000187:drug effects; D002856:Chromatophores / Q000187:drug effects*; D000242:Cyclic AMP / Q000494:pharmacology; D008116:Lizards; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D013045:Species Specificity
D000227:Adenine Nucleotides; D009074:Melanocyte-Stimulating Hormones; D000242:Cyclic AMP; D010744:Phosphoric Monoester Hydrolases