The influence of luteinizing hormone-releasing hormone (LHRH) on the process of protein and/or peptide secretion characterized by the formation of granular vesicles in mammalian pinealocytes. Comparative in vitro study.

In the present study, the effect of LHRH on the process of protein and/or peptide secretion characterized by the formation of granular vesicles has been studied by means of an in vitro system in the pinealocytes of three different species of rodents. LHRH has a strong influence on the activity of this process. However, this effect varies with the presence of noradrenaline (NA) in the medium and is not identical in the individual species studied. In the rat and mouse, for example, LHRH induces an increase in the number of granular vesicles when the pinealocytes are cultured in a NA-free medium, while, in contrast, in the hamster this stimulatory effect is found exclusively in the presence of NA. Moreover, in the pinealocytes of the mouse, in the presence of NA, LHRH shows an inhibitory effect on protein secretion. These results clearly demonstrate that LHRH, at least under the present in vitro conditions, acts on the synthetic activity of the pineal gland, and demonstrates the importance of pineal protein and/or peptide "hormones" in pineal endocrinology.