Effects of cyclic 3′,5′‐AMP and other adenine nucleotides on the melanophores of the lizard (Anolis carolinensis)

Abstract

. 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. . 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. . 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. . Other evidence supporting the first‐messenger—second‐messenger hypothesis for melanophore regulation is discussed. . 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.

Effects of Catecholamines on Metabolism

“…Melanocyte-stimulating hormone causes darkening of the frog skin. Theophylline (ABE et aI., 1969), cAMP and dBcAMP (NOVALES and DAVIS, 1967;HADLEY and GOLDMAN, 1969) mimic this effect. Stimulation of p-receptors by isopropylnoradrenaline or by salbutamol also causes darkening of the skin (GOLDMAN and HADLEY, 1969a and b).…”

The effects of cyclic adenosine 3',5'‐monophosphate and other adenine nucleotides on body temperature.

“…Kim, Shulman & Levine (1968) reported that Db-cAMP was less effective than cAMP in causing relaxation of the isolated rabbit ileum, and Ryan & Heidrick (1968) showed that Db-cAMP was less effective as an inhibitor of cell growth in tissue culture. There are, furthermore, several reports of Db-cAMP producing responses different from those of the parent compound on various preparations including skeletal muscle (Chambaut, Ebou6-Bonis, Hanoune & Clauser, 1969) melanophores (Hadley & Goldman, 1969), isolated fat cells (Solomon, Brush & Kitabehi, 1970), HeLa cells (Hilz & Tarnowski, 1970) and intestinal smooth muscle (Bowman & Hall, 1070). In the experiments reported here the actions of cAMP with Db-cAMP when injected into the hypothalamic region of the cat brain are compared.…”

Cyclic Nucleotides

“…Effects on glucose uptake in mammalian skeletal muscle (166), on glucose oxidation in fat cells (149 ), and on melanocyte dispersion in lizard skin (167 ) can be cited as examples here. Effects on glucose uptake in mammalian skeletal muscle (166), on glucose oxidation in fat cells (149 ), and on melanocyte dispersion in lizard skin (167 ) can be cited as examples here.…”