SOMATOSTATIN IMMUNOREACTIVE PEPTIDES OF HIGHER MOLECULAR WEIGHT IN OVINE HYPOTHALAMIC EXTRACTS

Abstract

U.C.T./M.R.C. Protein Research Unit, Department of Chemical Pathology, Medical School, Observatory 7925, Cape Town, Republic of South Africa (Received 26 January 1978) Higher molecular weight (HMW) immunoreactive forms of somatostatin have been reported in extracts of ovine hypothalami (Vale, Ling, Rivier, Villarreal, Rivier, Douglas & Brown, 1976), rat pancreas and stomach (Arimura, Sato, Dupont, Nishi & Schally, 1975) and human pancreatic somatostatinoma (Larsson, Hirsch, Holst, Ingemansson, Kühl, Jensen, Lundquist & Rehfeld, 1977). However, the possibility that the HMW immunoreactive substances were oligomers of somatostatin or somatostatin bound to larger molecules was not excluded. The present study was undertaken to establish that authentic HMW immunoreactive somatostatin is present in the ovine hypothalamus and to glean information on the structural relationship of the HMW species with somatostatin. Sheep hypothalami were extracted and subjected to gel permeation chromatography as described previously by Millar, Aehnelt & Rossier (1977). Fractions were assayed for somatostatin immunoreactivity