Evidence for the Existence of Separate Vasopressin and Oxytocin-containing Granules in the Neurohypophysis

Abstract

HISTOLOGICAL investigations have indicated that the peptide hormones, oxytocin and vasopressin, are associated with the neurosecretory substance observed in the hypothalamus, the hypothalamic-hypophysial stalk, and the posterior lobe of the pituitary¹. Hormonal activity may be sedimented from pituitary homogenates^2–4, substantiating claims that the octa-peptides are particle-bound. The variable ratio of pressor to oxytocic activity in different parts of the neurosecretory system⁵, and the report of Acher⁶ that protein-bound oxytocin in pituitary extracts can be separated from protein-bound vasopressin, have led to speculation that two particle types may exist. Pardoe and Weatherall² suggested that the oxytocic and pressor fractions are contained in different particles, since the conditions favouring maximal activity in centrifugation deposits were not the same for the two hormones.