The neurohypophysial principles of the western brook lamprey, Lampetra richardsoni: Studies in the adult

Abstract

Pharmacological and purification studies were carried out on lyophilised neurohypophysial tissues from Lampetra richardsoni and on control brain tissues. Crude neurohypophysial extracts contained 5.45 (4.41–6.73) mU/mg dry tissue of oxytocic activity; 3.27 mU/mg dry tissue appeared to be due to a neurohypophysial peptide which showed frog-bladder and other activities typical of arginine vasotocin (AVT). The use of trichloroacetic acid (TCA) and a carboxymethyl cellulose column resulted in a 190-fold purification of the peptide. Assay of the purified principle directly against synthetic AVT by different methods of assay suggested that it was AVT. Partition chromatography supported this finding. Control spinal cord tissues contained only low oxytocic activity (0.27 mU/mg dry tissue), but hindbrain materials showed the surprisingly high potency of 1.39 (1.19–1.62) mU/mg dry tissue. Purification of the hindbrain extract with TCA and carboxymethyl cellulose resolved an oxytocic agent with the thioglycollate lability and chromatographic and pharmacological properties of AVT. It amounted to approximately 0.18 mU/mg dry tissue, or only 12% of the total oxytocic activity present. The purification resolved small amounts of a number of oxytocic agents other than AVT. Some showed chromatographic similarities to oxytocin. However, none was destroyed by sodium thioglycollate. Any true neutral neurohypophysial principle could not have amounted to more than 1% of the AVT present (in terms of oxytocic activity), and there was no positive evidence for its existence in the neurohypophysis. The results suggest that AVT is the only neurohypophysial principle of L. richardsoni.