Current Status of Pineal Peptides

Abstract

In his comprehensive monograph on pineal chemistry, Quay suggested an intracellular site of action for MEL [melatonin]. Current experimentation strongly supports such an hypothesis. It is clear that the pineal glands of a variety of species contain identified and unidentified non-MEL substances which may also play an important role in pineal physiology. Whereas the significance of the presence of hypothalamic releasing factors in the pineal is enigmatic, AVT [arginine vasotocin] assumes more readily a physiological role since various antigonadotropic activities are ascribed to this molecule. Whether AVT is the pineal gonadotropin is discussed. The evidence that unidentified peptides are detectable in pineal tissue is important and suggestive that substances other than MEL and AVT may be antigonadotropic. The inconclusive evidence is based mainly on the methods of extraction, which in certain cases appears ideal for peptides, and positive reactivity to non-specific reagents like ninhydrin. The susceptibility to digestion by proteolytic enzymes of the antigonadotropin, and its positive staining with peptide reagent, argue strongly in favor of its peptidic nature. Similar to the quantities of releasing factors 1st recovered from hypothalamic tissue, this antigonadotropin is recoverable from pineal extracts in small quantities. Large scale preparative methods will be required for structural determination.