N-Acetyltransferase activity of the rat Harderian gland.

Harderian gland extracts from male rats catalyze the conversion of serotonin to N-acetylserotonin and of tryptamine to N-acetyltryptamine. The reaction is linear up to 14 mg tissue and departs from linearity after 10 min. The pH otpimum with tryptamine as substrate is between 8 and 9. Enzymic activity of the gland in vivo does not show diurnal variations. Enzymic activity of tissue in organ culture is not stimulated by 10 micrometer isoproterenol or 100 micrometer dibutyryl cyclic AMP. Harderian gland tissue in culture can acetylate tryptamine and serotonin and can O-methylate the N-acetylserotonin to form melatonin.