Regulation of tyrosine aminotransferase activity by glucagon and cAMP analogues in chick embryos in ovo.
Glucagon, dibutyryl cAMP (Bt2cAMP) and 8-(4-chlorophenylthio) cAMP (CptcAMP), singly or when combined, stimulated tyrosine aminotransferase (TAT) activity in 17-day-old chick embryos in ovo. Maximal induction was produced within 4 hr of injection of the inducers. The effects of glucagon and the cAMP analogues were not additive. Glucagon administration was accompanied by a rapid increase in hepatic cAMP concentration which remained elevated for at least 4 hr. The stimulated increase in TAT activity elicited by the hormone or cyclic nucleotide was prevented by injection of cycloheximide or cordycepin. These results are discussed vis-à-vis the possible regulation of TAT in ovo by physiological concentrations of glucagon and the likely role of cAMP as a second messenger in this process during chick embryogenesis.
Onoagbe
I O
IO
Department of Biochemistry, University of Benin, Nigeria.
Okolie
P N
PN
Onyeneke
E C
EC
Dickson
A J
AJ
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D002478:Cells, Cultured; D002642:Chick Embryo / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D003513:Cycloheximide / Q000633:toxicity; D003839:Deoxyadenosines / Q000633:toxicity; D004338:Drug Combinations; D004790:Enzyme Induction / Q000187:drug effects; D005934:Glucagon / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009153:Mutagens / Q000633:toxicity; D015290:Second Messenger Systems; D013056:Spectrophotometry, Ultraviolet; D013873:Thionucleotides / Q000494:pharmacology*; D014444:Tyrosine Transaminase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*
D003839:Deoxyadenosines; D004338:Drug Combinations; D009153:Mutagens; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D003994:Bucladesine; D005934:Glucagon; D003513:Cycloheximide; D000242:Cyclic AMP; D014444:Tyrosine Transaminase; C058120:cordycepin