Rhythmic expression, light entrainment and alpha-MSH modulation of rhodopsin mRNA in a teleost pigment cell line.
To investigate whether teleost fish GEM-81 erythrophoroma cells were photosensitive, the cells were submitted to constant darkness (DD), 14 h of light and 10 h of darkness (14L:10D), and 10 h of light and 14 h of darkness (10L:14L). The doubling times (hours) were: DD 35.33+/-0.05; 14L:10D 67.85+/-0.04; and 10L:14D 49.60+/-0.08. In order to verify whether proliferation was dependent on light phase length, GEM-81 cells were submitted to 7L: 5D. The proliferation curves and doubling times were similar in 14L:10D and 7L:5D (respectively 69.44+/-0.03 and 67.85+/-0.04), suggesting that the cell cycle was regulated by the length of the light phase within 24 h, or by the light/dark ratio. We have also demonstrated the expression of Carassius retinal rhodopsin mRNA in GEM-81 cells, which cycles in a circadian rhythm, entrained by light. In addition, we showed that alpha-melanocyte stimulating hormone (alpha-MSH, 10(-10) to 10(-8) M), a conspicuous hormone that exerts mitogenic and melanogenic activity in most vertebrates, decreased rhodopsin mRNA in the first 3 days; after 4 days the inhibition was reversed, and after 5 days an increase in rhodopsin mRNA level was elicited. This is the first report of rhythmic expression of extra-ocular rhodopsin and its modulation by light and hormones.
Im
Letícia Hyoo Jung
LHJ
Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
Isoldi
Mauro Cesar
MC
Department of Biology, University of Virginia, Charlotesville, VA, USA.
Scarparo
Ana Cristina
AC
Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
Visconti
Maria Aparecida
MA
Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
de Lauro Castrucci
Ana Maria
AM
Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil; Department of Biology, University of Virginia, Charlotesville, VA, USA. Electronic address: amdlcast@ib.usp.br.
D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002940:Circadian Rhythm / Q000187:drug effects* / Q000528:radiation effects*; D003624:Darkness; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D006054:Goldfish / Q000235:genetics*; D008027:Light; D008544:Melanocytes / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects; D017440:Photoperiod; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012243:Rhodopsin / Q000235:genetics* / Q000378:metabolism; D000521:alpha-MSH / Q000494:pharmacology*
D012333:RNA, Messenger; D000521:alpha-MSH; D012243:Rhodopsin