Arylamine and arylalkylamine N-acetyltransferases in retina, pineal gland, brain and liver of chicks: a comparative study.
Regulation of arylamine N-acetyltransferase (A-NAT) and arylalkylamine N-acetyltransferase (AA-NAT) was examined in retina, pineal gland, brain and liver of chicks. Enzyme activities were determined using as substrates p-phenetidine and procainamide for A-NAT, tryptamine and phenethylamine for AA-NAT. The activity of A-NAT in all tissues studied does not appear to be regulated by a light-dark cycle. On the other hand, AA-NAT showed distinct light-dark dependent changes (with high values at night) in the retina and pineal gland, but not in brain and liver. The nocturnal increase of retinal and pineal AA-NAT activity was prevented by cycloheximide; the drug did not affect A-NAT activity in these tissues. Treatment of light-adapted chicks with aminophylline significantly increased AA-NAT activity of the retina and pineal gland, without altering the enzyme activity in brain and liver. In these animals, the activity of A-NAT (procainamide) did not change in any tissue studied, whereas the enzyme activity measured using p-phenetidine as a substrate did decrease but only in the retina. A similar pattern of changes in retinal A-NAT and AA-NAT activities was observed after intraocular injection of d,b-cAMP. The rate of inactivation at 4 degrees C was significantly slower for AA-NAT than A-NAT. NATs from brain and liver displayed the highest and lowest, respectively, liability in the cold. The results indicate that the chick retina contains both A-NAT and AA-NAT. The two enzymes have distinct characteristics and the regulation of their activities is different. The retinal A-NAT is similar to A-NAT present in other tested tissues; however, AA-NAT can be induced at night only in the retina and pineal gland. It is suggested that there are two forms of retinal A-NAT, and that, under specified conditions, the activity of one form (A-NAT; p-phenetidine) may be regulated in an opposite manner to AA-NAT activity.
Nowak
J Z
JZ
Department of Biogenic Amines, Polish Academy of Sciences, Lódź-1, Poland.
Zawilska
J B
JB
Woldan-Tambor
A
A
D000704:Analysis of Variance; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D001921:Brain / Q000201:enzymology*; D003994:Bucladesine / Q000494:pharmacology; D002645:Chickens; D002940:Circadian Rhythm; D003513:Cycloheximide / Q000494:pharmacology; D003624:Darkness; D007700:Kinetics; D008027:Light; D008099:Liver / Q000201:enzymology*; D008297:Male; D009928:Organ Specificity; D010870:Pineal Gland / Q000201:enzymology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012160:Retina / Q000201:enzymology*; D013379:Substrate Specificity
D011500:Protein Synthesis Inhibitors; D003994:Bucladesine; D003513:Cycloheximide; D001191:Arylamine N-Acetyltransferase