A Substance Resembling Arginine Vasotocin in the Anterior Pituitary Gland of the Cockerel

Fractionation by ultrafiltration of acid extracts of cockerel adenohypophyses revealed 2 components which depleted ovarian ascorbic acid (OAA) in the appropriately pretreated assay rat. Avian LH was retained in the large molecular weight (over 12,000) fraction. In the 32P assay, this fraction evoked a response curve which was parallel to that of the NIH-LH standard. The other fraction, which contained molecules with a molecular weight of less than 12,000, caused depletion of OAA in both intact and hypophysectomized assay rats, but was inactive when tested for its ability to increase 32P uptake by the chick testis. Thus, its OAA depleting activity was due neither to luteinizing hormone (LH) nor to LH-releasing factor. Fractionation of the small molecules on a column of Sephadex G-25 revealed a potent OAA depleting compound with the additional following characteristics: 1) same elution volume as synthetic arginine vasotocin (AVT), 2) potent vasopressor activity, 3) inactivated by thioglycollate. These data have 2 major implications: 1) The OAA depleting assay is not a valid index for measuring LH in the chick adenohypophysis, and 2) there appear to be comparatively large quantities of a substance resembling AVT in the anterior lobe. The physiological importance of these findings is yet obscure. (Endocrinology84: 1218, 1969)