Inhibitory effect of epinephrine on phosphatidate activity in isolated rat hepatocytes.
The variations in phosphatidate phosphohydrolase activity were investigated in the post-mitochondrial fraction of isolated rat hepatocytes incubated for short periods with epinephrine, dibutyryl cyclic AMP or oleate. Epinephrine decreased the enzyme activity by 42% at 1 microM concentration. The inhibitory effect was abolished in the presence of a beta-adrenoceptor antagonist, propranolol, but was not affected by the alpha-adrenoceptor agonist, phenylephrine, or the agonist, phentolamine. Dibutyryl-cAMP inhibited the enzyme activity by 49%. The presence of the cyclic-AMP phosphodiesterase inhibitor, aminophyline, together with epinephrine slightly increased the enzyme inhibition. Oleate stimulated the enzyme activity (100%) and its effect was antagonized by dibutyryl-cyclic AMP (24%) and by epinephrine (15%). The results indicate that epinephrine acts on rat hepatocytes via beta-adrenoceptor activation and cAMP may be involved in the mechanism by which phosphatidate phosphohydrolase is regulated.
Haghighi
B
B
Department of Biochemistry, University of Isfahan, Iran.
Raspuli
M
M
Suzangar
M
M
D000818:Animals; D002469:Cell Separation; D002478:Cells, Cultured / Q000187:drug effects / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D010711:Phosphatidate Phosphatase / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010711:Phosphatidate Phosphatase; D004837:Epinephrine