The proteinaceous content and possible physiological significance of dense-cored vesicles in hamster and mouse pinealocytes

Electron dense-cored vesicles (DCV), originating in the Golgi apparatus and migrating into the perivascular processes, constitute a characteristic feature of the pinealocytes in the pineal gland of mice and hamsters. This report presents the results of ultracytochemical studies carried out to clarify the nature and physiological significance of these vesicles. Using proteases and the PA-TCH-silver technique on ultrathin sections, it was concluded that the dense core of DCV was proteinaceous in nature. These data, correlated with previous pharmacological and cytophysiological studies, showed the important role of DCV in the storage and intracellular migration of a proteinaceous compound of unknown significance. However, in agreement with authors who hypothesized the elaboration of active peptidergic compounds in the mammalian pineal gland to explain some effects that could not be ascribed to indoleamines, it was proposed that DCV might store a carrier-neurohormone complex. The presence in the DCV of one indoleamine, such as serotonin, or of several indoleamines, has still not been established in mammals.