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Characterization of prolactin-releasing factor in the rat posterior pituitary.
Endocrinology. 1988 Jun; 122(6):2533-9.E

Abstract

We previously reported that the rat posterior pituitary contains a potent PRL-releasing factor (PRF) which is distinct from oxytocin (OT), TRH, and angiotensin II (AII). The objectives of this study were 1) to examine whether posterior pituitary extracts stimulate PRL release in the presence of dopamine (DA), 2) to determine the chemical nature of PRF, and 3) to estimate its mol wt. Perifused anterior pituitary cells were used to assess PRF activity. Posterior pituitaries and medial basal hypothalamus (MBH) fragments were extracted with perchloric acid and lyophilized. Subsequent to various treatments, samples were reconstituted in the perifusion medium and introduced to the cells in short pulses. Fractions were collected and analyzed for hormone content by RIA. During a constant infusion of DA (50 nM), PRL secretion was inhibited by 75%, yet the posterior pituitary extract retained its ability to rapidly stimulate PRL release. Studies using proteolytic enzymes showed that posterior pituitary PRF was resistant to inactivation by trypsin, whereas the PRF activity of AII was abolished. Both chymotrypsin and proline-specific endopeptidase significantly reduced the PRF activity in the posterior pituitary. The PRL-releasing activity of TRH was not affected by chymotrypsin. Immunoreactive vasoactive intestinal polypeptide was undetectable in posterior pituitary extracts. Oxidation of posterior pituitary extracts with performic acid caused only a modest reduction of their PRF activity, while the ability of OT to stimulate PRL release as well as immunoreactive OT was abolished. Studies using ultrafiltration membranes showed that the PRF activity in the posterior pituitary was less than 5,000 mol wt. Furthermore, posterior pituitary PRF partitioned in nearly equal amounts across 1K membranes, as did AII and OT. In contrast, about 80% of the PRF activity in the MBH and all of the synthetic TRH passed through the 1K membranes. We conclude that 1) posterior pituitary PRF can stimulate PRL secretion from perifused anterior pituitary cells in the presence of physiological concentrations of DA; 2) PRF is a small peptide(s) of less than 5,000, and perhaps closer to 1,000, mol wt; 3) PRF is resistant to inactivation by trypsin and to oxidation by performic acid, but is hydrolyzed by both chymotrypsin and proline-specific endopeptidase; and 4) these data further distinguish posterior pituitary PRF from known PRL secretagogues.

Authors+Show Affiliations

Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46223.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

3131118

Citation

Hyde, J F., and N Ben-Jonathan. "Characterization of Prolactin-releasing Factor in the Rat Posterior Pituitary." Endocrinology, vol. 122, no. 6, 1988, pp. 2533-9.
Hyde JF, Ben-Jonathan N. Characterization of prolactin-releasing factor in the rat posterior pituitary. Endocrinology. 1988;122(6):2533-9.
Hyde, J. F., & Ben-Jonathan, N. (1988). Characterization of prolactin-releasing factor in the rat posterior pituitary. Endocrinology, 122(6), 2533-9.
Hyde JF, Ben-Jonathan N. Characterization of Prolactin-releasing Factor in the Rat Posterior Pituitary. Endocrinology. 1988;122(6):2533-9. PubMed PMID: 3131118.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Characterization of prolactin-releasing factor in the rat posterior pituitary. AU - Hyde,J F, AU - Ben-Jonathan,N, PY - 1988/6/1/pubmed PY - 1988/6/1/medline PY - 1988/6/1/entrez SP - 2533 EP - 9 JF - Endocrinology JO - Endocrinology VL - 122 IS - 6 N2 - We previously reported that the rat posterior pituitary contains a potent PRL-releasing factor (PRF) which is distinct from oxytocin (OT), TRH, and angiotensin II (AII). The objectives of this study were 1) to examine whether posterior pituitary extracts stimulate PRL release in the presence of dopamine (DA), 2) to determine the chemical nature of PRF, and 3) to estimate its mol wt. Perifused anterior pituitary cells were used to assess PRF activity. Posterior pituitaries and medial basal hypothalamus (MBH) fragments were extracted with perchloric acid and lyophilized. Subsequent to various treatments, samples were reconstituted in the perifusion medium and introduced to the cells in short pulses. Fractions were collected and analyzed for hormone content by RIA. During a constant infusion of DA (50 nM), PRL secretion was inhibited by 75%, yet the posterior pituitary extract retained its ability to rapidly stimulate PRL release. Studies using proteolytic enzymes showed that posterior pituitary PRF was resistant to inactivation by trypsin, whereas the PRF activity of AII was abolished. Both chymotrypsin and proline-specific endopeptidase significantly reduced the PRF activity in the posterior pituitary. The PRL-releasing activity of TRH was not affected by chymotrypsin. Immunoreactive vasoactive intestinal polypeptide was undetectable in posterior pituitary extracts. Oxidation of posterior pituitary extracts with performic acid caused only a modest reduction of their PRF activity, while the ability of OT to stimulate PRL release as well as immunoreactive OT was abolished. Studies using ultrafiltration membranes showed that the PRF activity in the posterior pituitary was less than 5,000 mol wt. Furthermore, posterior pituitary PRF partitioned in nearly equal amounts across 1K membranes, as did AII and OT. In contrast, about 80% of the PRF activity in the MBH and all of the synthetic TRH passed through the 1K membranes. We conclude that 1) posterior pituitary PRF can stimulate PRL secretion from perifused anterior pituitary cells in the presence of physiological concentrations of DA; 2) PRF is a small peptide(s) of less than 5,000, and perhaps closer to 1,000, mol wt; 3) PRF is resistant to inactivation by trypsin and to oxidation by performic acid, but is hydrolyzed by both chymotrypsin and proline-specific endopeptidase; and 4) these data further distinguish posterior pituitary PRF from known PRL secretagogues. SN - 0013-7227 UR - https://www.unboundmedicine.com/medline/citation/3131118/Characterization_of_prolactin_releasing_factor_in_the_rat_posterior_pituitary_ L2 - https://academic.oup.com/endo/article-lookup/doi/10.1210/endo-122-6-2533 DB - PRIME DP - Unbound Medicine ER -