Localization of indoleamine and protein synthesis in the mammalian pineal gland

In a table, conditions and compounds have been listed either known or suggested to influence pineal function. In the same model, systems and organs and their products are indicated the function or, respectively, the quantity of which are known or suggested to be influenced by pineal secretory substances. Of the latter, indoleamines and polypeptides are mentioned only although it is now known that also other low molecular weight biologically active compounds are produced by the gland. Problems relating to the localization of indoleamine and protein synthesis in the pinealocyte are discussed. The synthesis of indoleamines, at least of serotonin, may occur freely in the cytosol although, especially in non-mammals, the presence of serotonin seems to be preferentially, but perhaps secondarily, related to the secretory dense-core vesicles. Questions concerning the exact function of pineal melatonin are shortly dealt with. The granules of the secretory vesicles probably also contain a proteinaceous substance which, notwithstanding its unknown chemical nature, has been considered the antigonadotropic principle by some authors. Recent investigations on the production of active proteinaceous compounds in cisterns of the endoplasmic reticulum and between the layers of the nuclear envelope are reviewed. These substances are not concentrated in secretory granular vesicles, so scarce in the pinealocyte which proteinaceous active principle is produced in still largely unsolved as is their exact chemical composition.