title: Circadian-time rhythm of hepatic protein kinase C of rats pretreated with phenobarbital.
abstract: Circadian-time dependent differences of protein kinase C (PKC) activities as well as its susceptibility to a phenobarbital caused suppression in vivo (40 mg/kg b.i.d. for 3 days) were studied in outbred male Wistar rats weighing 280-360 g. The well-known phenobarbital induction of cytochrome P-450 and 7-pentylresorufin-O-depentylase (PROD) was associated with inhibition of the hepatic PKC. The activities of the cytosolic and membrane-bound PKC were significantly lower than in the respective controls. Statistically significant circadian-time differences were found. The activities of both cytosolic and membrane-bound PKC of control rats were highest in the evening (158% and 131%, respectively, of the morning values). Furthermore, phenobarbital inhibited the enzyme more strongly at 19.00 h than at 07.00 h. Our results suggest that increase of hepatic cytochrome P-450 content as well as induction of PROD are inversely related with the function of PKC.
authors.affiliation: Institut für Pharmakologie, Medizinische Fakultät, Ernst-Moritz-Arndt- Universität Greifswald.
authors.forename: K U
authors.initials: KU
authors.lastname: Möritz
authors.forename: R
authors.initials: R
authors.lastname: Walter
authors.forename: G
authors.initials: G
authors.lastname: Franke
authors.forename: W
authors.initials: W
authors.lastname: Siegmund
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002940:Circadian Rhythm / Q000502:physiology*; D019362:Cytochrome P-450 CYP2B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D009929:Organ Size / Q000187:drug effects; D010088:Oxidoreductases / Q000096:biosynthesis; D010634:Phenobarbital / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019362:Cytochrome P-450 CYP2B1; D011493:Protein Kinase C; D010634:Phenobarbital