TY - JOUR
T1 - Comparative biological activities of α-MSH antagonists in vertebrate pigment cells
AU - Castrucci, Ana Maria De L.
AU - Almeida, Ana Luisa K.
AU - Al-Obeidi, Fahad A.
AU - Hadley, Mac E.
AU - Hruby, Victor J.
AU - Staples, Douglas J.
AU - Sawyer, Tomi K.
N1 - Funding Information:
This work has been partially supported by FAPESP, FINEP and CNPq, and U.S. Public Health Service Grant DK-17420.
PY - 1997/3
Y1 - 1997/3
N2 - We have previously reported that melatonin was an effective lightening agonist in the teleost Synbranchus marmoratus, the amphibians Rana pipiens and Bufo ictericus, and in the lizard Anolis carolinensis. The hormone, previously applied to the preparations, effectively inhibited α-MSH darkening activity in a dose-independent manner, and was also able to reverse MSH-induced darkening. We presently describe the inhibitory effect of the indoleamine on the murine melanoma cell proliferation. Interestingly, the hormone also stimulated tyrosinase activity, with a correlated increase in melanin content. We also demonstrate that in a diverse lizard species, Urosaurus ornatus, the indoleamine was totally ineffective. The competitive MSH antagonistic activity of H-His-D-Arg-Ala-Trp-D-Phe-Lys-NH2 has been demonstrated previously in R. pipiens and U. ornatus. Herein, its inhibitory activity is also reported in another lizard species, A. carolinensis. However, this MSH analogue was inactive in S. marmoratus, and in murine melanoma cells. On the other hand, the 7 thru 10 α-MSH fragment, Ac-Phe- Arg-Trp-Gly-NH2, although ineffective in S. marmoratus and R. pipiens, was an α-MSH antagonist in A. carolinensis. Surprisingly, in the melanoma cell line, the MSH fragment exhibited no agonist or antagonist activity, but dramatically potentiated the MSH-induced increase in tyrosinase activity. These data might suggest that the fragment is participating either in the process of facilitation or in positive cooperativity. The present results, taken together with our previously reported data, demonstrate a major interspecies diversity of the MC1 subtype of melanocortin receptor, and point out the relevance of the membrane microenvironment for the final receptor configuration.
AB - We have previously reported that melatonin was an effective lightening agonist in the teleost Synbranchus marmoratus, the amphibians Rana pipiens and Bufo ictericus, and in the lizard Anolis carolinensis. The hormone, previously applied to the preparations, effectively inhibited α-MSH darkening activity in a dose-independent manner, and was also able to reverse MSH-induced darkening. We presently describe the inhibitory effect of the indoleamine on the murine melanoma cell proliferation. Interestingly, the hormone also stimulated tyrosinase activity, with a correlated increase in melanin content. We also demonstrate that in a diverse lizard species, Urosaurus ornatus, the indoleamine was totally ineffective. The competitive MSH antagonistic activity of H-His-D-Arg-Ala-Trp-D-Phe-Lys-NH2 has been demonstrated previously in R. pipiens and U. ornatus. Herein, its inhibitory activity is also reported in another lizard species, A. carolinensis. However, this MSH analogue was inactive in S. marmoratus, and in murine melanoma cells. On the other hand, the 7 thru 10 α-MSH fragment, Ac-Phe- Arg-Trp-Gly-NH2, although ineffective in S. marmoratus and R. pipiens, was an α-MSH antagonist in A. carolinensis. Surprisingly, in the melanoma cell line, the MSH fragment exhibited no agonist or antagonist activity, but dramatically potentiated the MSH-induced increase in tyrosinase activity. These data might suggest that the fragment is participating either in the process of facilitation or in positive cooperativity. The present results, taken together with our previously reported data, demonstrate a major interspecies diversity of the MC1 subtype of melanocortin receptor, and point out the relevance of the membrane microenvironment for the final receptor configuration.
UR - http://www.scopus.com/inward/record.url?scp=0031104923&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031104923&partnerID=8YFLogxK
U2 - 10.1006/gcen.1996.6844
DO - 10.1006/gcen.1996.6844
M3 - Article
C2 - 9073503
AN - SCOPUS:0031104923
SN - 0016-6480
VL - 105
SP - 410
EP - 416
JO - General and comparative endocrinology
JF - General and comparative endocrinology
IS - 3
ER -