Effects of pineal indoles and arginine vasotocin on lipolysis and lipogenesis in isolated adipocytes.

The effects of arginine vasotocin and the pineal indoles melatonin, serotonin, N-acetylserotonin, hydroxytryptophol, methoxytryptophol, hydroxyindoleacetic acid, methoxyindoleacetic acid, and methoxytryptamine on lipolysis and lipogenesis in isolated adipocytes were studied. Basal lipolysis was inhibited by all the indoles tested at a dose of 1 mumole except hydroxytryptophol. Methoxytryptamine and serotonin inhibited hormone-induced lipolysis in a dose-dependent manner and exhibited the highest antilipolytic activity in isolated rat, rabbit, and hamster adipocytes. However, their antilipolytic activity could not be overcome by increasing the dose of the lipolytic hormone. Dibutyryl cyclic AMP-induced lipolysis was also inhibited. All the pineal indoles tested were capable of suppressing basal and insulin-stimulated lipogenesis in the dose range 0.33-3 nmole. At lower doses there was no effect. Arginine vasotocin at a dose of 25 nmole significantly augmented basal lipogenesis.