Biological and chemical evidence for the existence of a porcine hypothalamic parotid hormone-releasing factor.

Methodology has been developed to achieve partial purification of a parotid hormone-releasing peptide from porcine hypothalamus-thalamus tissue using an in vivo parotid hormone stimulation test in pigs and a dentinal fluid transport stimulation test in rats. The purification steps include: acetone-water extraction of the tissue at pH 5.2, ultrafiltration through Amicon PM10 membrane, size exclusion chromatography on Bio-Gel P2, and open-column reversed-phase chromatography on Lichroprep RP8. A 100-fold increase in specific activity was attained. Intravenous infusion of porcine hypothalamus-thalamus extract stimulates a dentinal fluid transport mechanism in teeth of intact anesthetized rats, and the release of plasma immunoreactive parotid hormone in conscious catheterized pigs. Parotidectomy in both species suppresses the response, suggesting that the expression of parotid hormone-releasing activity requires the integrity of a putative hypothalamus-parotid gland endocrine axis.