Diurnal variation in p42/44 mitogen-activated protein kinase in the rat pineal gland.
In this study, we investigated whether there was a diurnal difference in mitogen-activated protein kinase (p42/44(MAPK)) phosphorylation in the rat pineal gland. Under a lighting regimen with 12h of darkness, there was a two- to four-fold increase in phosphorylated levels of MAPK kinase 1/2 (MEK1/2) and p42/44(MAPK) 2h after onset of darkness, an increase that was sustained for 8h. The increases in phosphorylated levels of MEK1/2 and p42/44(MAPK) occurred without increases in MEK1/2 and p42/44(MAPK) proteins. When rats were treated with propranolol 1h before onset of darkness or subjected to continuous light exposure during the dark phase, the nocturnal increase in MEK1/2 and p42/44(MAPK) phosphorylation was reduced. Acute light exposure during darkness caused a decline in MEK1/2 and p42/44(MAPK) phosphorylation within 30 min of light exposure. These results indicate the presence of a diurnal difference in MEK1/2 and p42/44(MAPK) phosphorylation in the rat pineal gland that is under adrenergic control.
Department of Physiology, Faculty of Medicine, 7-26 Medical Sciences Building, University of Alberta, Edmonton, Alta., Canada T6G 2H7. anho@ualberta.ca
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D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D002940:Circadian Rhythm; D008027:Light; D019950:Mitogen-Activated Protein Kinase 1 / Q000032:analysis / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010870:Pineal Gland / Q000201:enzymology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats
D011433:Propranolol; D001191:Arylamine N-Acetyltransferase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases