Use of Receptor Affinity Chromatography in Purification of the Growth Hormone-Like Factor Produced by Plerocercoids of the Tapeworm Spirometra Mansonoides

Abstract

The plerocercoid stage of the tapeworm Spirometra mansonoides produces a functional analog of human growth hormone (hGH). Among the similarities between plerocercoid growth factor (PGF) and hGH is competition for the same receptors on rabbit liver membranes. To take advantage of this characteristic in a purification scheme for PGF, rabbit liver microsomes were solubilized in Triton X-100 and the hGH receptors were purified over an hGH affinity column. The purified receptors from six rabbit livers were coupled to Affi-Gel-10 to create a receptor affinity column which was used to purify PGF. Chromatography of crude PGF over the receptor column resulted in a 1044 fold increase in specific activity. SDS-PAGE in the presence of 2-mercaptoethanol showed that the affinity-purified PGF contained three protein bands with apparent M_rs of 27.5 K, 22 K, and 16.7 K. Injections of the partially-purified PGF into hypophysectomized rats produced a dose-dependent growth response and 400 ng eq of PGF each day for 10 days stimulated a growth response not significantly different from that produced by 250 μg of bovine GH each day. Receptor affinity chromatography was an effective method to purify small amounts of PGF in a single step with negligible loss of biological activity.