Melatonin formation in rat pineal gland organ culture: induction by an adrenergic beta 2-stimulating drug.

It is well known that the pineal gland hormone melatonin has a direct effect on pigment dispersion in amphibian melanocytes. This pineal hormone has also been reported to influence pituitary melanocyte-stimulating hormone (MSH) activity in the rat. Melatonin is formed from serotonin (5-hydroxytryptamine) in two metabolic steps: first, serotonin is enzymatically metabolized by N-acetyltransferase to N-acetylserotonin, and second, this is converted to melatonin by hydroxy-indole-O-methyltransferase (HIOMT). The N-acetyl-transferase activity may be induced by stimulation of a j3-adrenergic mechanism. In the present experiment we tested the ability of the p-adrenerg c stimulating drug, isoprenalin (INN, NFN)