Daily variations of blood glucose, acid-base state and PCO2 in rats: effect of light exposure.
The suprachiasmatic nuclei (SCN) of the hypothalamus are the site of the main circadian clock in mammals. Synchronization of the SCN to light is achieved by direct retinal inputs. The present study performed in rats transferred to constant darkness shows that blood glucose, pH and PCO2 display significant diurnal changes when measurements were made during the subjective day, the early subjective night or the late subjective night. The effects of a 30-min light exposure (100 lx) on these metabolic parameters at each of these circadian times were assessed. Regardless of the circadian time, light induced an increase in blood glucose, but did not affect plasma pH and PCO2. This study suggests that blood glucose, PCO2 and acid-base state are under circadian control, most likely mediated by the SCN, while the hyperglycemic response to light seems not to be gated by a circadian clock and may thus involve retinal inputs to non-SCN retino-recipient areas.
Challet
Etienne
E
Laboratory of Neurobiology of Rhythms, Centre National de la Recherche Scientifique (UMR 7518), Department of Neuroscience (IFR37), Université Louis Pasteur, 12 rue de l'Université, F-67000 Strasbourg, France. challet@neurochem.u-strasbg.fr
Malan
André
A
Turek
Fred W
FW
Van Reeth
Olivier
O
D000136:Acid-Base Equilibrium / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D001786:Blood Glucose / Q000502:physiology* / Q000528:radiation effects; D002245:Carbon Dioxide / Q000097:blood*; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects; D003624:Darkness; D008027:Light; D008297:Male; D010775:Photic Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000502:physiology / Q000528:radiation effects; D012683:Sensory Deprivation / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000502:physiology* / Q000528:radiation effects; D015854:Up-Regulation / Q000502:physiology / Q000528:radiation effects; D014795:Visual Pathways / Q000502:physiology / Q000528:radiation effects
D001786:Blood Glucose; D002245:Carbon Dioxide