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The effect of relaxin infusion on prolactin and growth hormone secretion in monkeys.
J Clin Endocrinol Metab 1989; 69(5):956-62JC

Abstract

To test the hypothesis that relaxin may affect pituitary hormone secretion, synthetic human relaxin was infused into cycling and pregnant rhesus monkeys. Doses ranging from 0.154-1540 ng/kg.min were calculated to achieve circulating relaxin concentrations of 1 pM to 10 nM. Low (0.154 and 1.54 ng/kg.min), intermediate (15.4 and 154 ng/kg.min), and high (1540 ng/kg.min) doses of relaxin were infused for 15 min each hour into ovulating monkeys at the midluteal phase of the menstrual cycle in two separate experiments. Serum GH and PRL were measured by RIA, and serum relaxin was determined by enzyme-linked immunosorbent assay. Relaxin was undetectable in peripheral plasma during the control saline infusion and during infusion of the lowest dose of relaxin. Serum relaxin levels reached 0.011, 0.119, 0.965, and 13.0 nM with 1.54, 15.4, 154, and 1540 ng/kg.min, respectively. Serum GH was significantly elevated over basal levels upon infusion of relaxin from 1.54-1540 ng/kg.min; however, a plateau was observed with the intermediate doses, and a decrease in the magnitude of the response was observed at the highest dose. Serum PRL increased over basal levels with 15.4 and 154 ng/kg.min, but there was no difference in the magnitude of the increase between these doses. PRL levels during infusion of the highest dose of relaxin were similar to control levels. These data suggest that relaxin can stimulate secretion of GH and PRL in cycling monkeys within a defined dose range, but that a decrease in pituitary responsiveness occurs at higher doses. One high dose of relaxin (2600 ng/kg.min) was infused for 1 h into the maternal and then the fetal circulations of chronically catheterized and tethered pregnant monkeys between 120-140 days gestation. Upon infusion of relaxin into the maternal circulation, there was a significant elevation of PRL in the mother but not the fetus. Upon infusion of relaxin into the fetus, there was no consistent change in PRL secretion in either the mother or the fetus. In conclusion, relaxin may have a heretofore undescribed role in pituitary physiology during the menstrual cycle and in pregnancy.

Authors+Show Affiliations

Division of Reproductive Biology and Behavior, Oregon Regional Primate Research Center, Beaverton 97006.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

2793997

Citation

Bethea, C L., et al. "The Effect of Relaxin Infusion On Prolactin and Growth Hormone Secretion in Monkeys." The Journal of Clinical Endocrinology and Metabolism, vol. 69, no. 5, 1989, pp. 956-62.
Bethea CL, Cronin MJ, Haluska GJ, et al. The effect of relaxin infusion on prolactin and growth hormone secretion in monkeys. J Clin Endocrinol Metab. 1989;69(5):956-62.
Bethea, C. L., Cronin, M. J., Haluska, G. J., & Novy, M. J. (1989). The effect of relaxin infusion on prolactin and growth hormone secretion in monkeys. The Journal of Clinical Endocrinology and Metabolism, 69(5), pp. 956-62.
Bethea CL, et al. The Effect of Relaxin Infusion On Prolactin and Growth Hormone Secretion in Monkeys. J Clin Endocrinol Metab. 1989;69(5):956-62. PubMed PMID: 2793997.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The effect of relaxin infusion on prolactin and growth hormone secretion in monkeys. AU - Bethea,C L, AU - Cronin,M J, AU - Haluska,G J, AU - Novy,M J, PY - 1989/11/1/pubmed PY - 1989/11/1/medline PY - 1989/11/1/entrez SP - 956 EP - 62 JF - The Journal of clinical endocrinology and metabolism JO - J. Clin. Endocrinol. Metab. VL - 69 IS - 5 N2 - To test the hypothesis that relaxin may affect pituitary hormone secretion, synthetic human relaxin was infused into cycling and pregnant rhesus monkeys. Doses ranging from 0.154-1540 ng/kg.min were calculated to achieve circulating relaxin concentrations of 1 pM to 10 nM. Low (0.154 and 1.54 ng/kg.min), intermediate (15.4 and 154 ng/kg.min), and high (1540 ng/kg.min) doses of relaxin were infused for 15 min each hour into ovulating monkeys at the midluteal phase of the menstrual cycle in two separate experiments. Serum GH and PRL were measured by RIA, and serum relaxin was determined by enzyme-linked immunosorbent assay. Relaxin was undetectable in peripheral plasma during the control saline infusion and during infusion of the lowest dose of relaxin. Serum relaxin levels reached 0.011, 0.119, 0.965, and 13.0 nM with 1.54, 15.4, 154, and 1540 ng/kg.min, respectively. Serum GH was significantly elevated over basal levels upon infusion of relaxin from 1.54-1540 ng/kg.min; however, a plateau was observed with the intermediate doses, and a decrease in the magnitude of the response was observed at the highest dose. Serum PRL increased over basal levels with 15.4 and 154 ng/kg.min, but there was no difference in the magnitude of the increase between these doses. PRL levels during infusion of the highest dose of relaxin were similar to control levels. These data suggest that relaxin can stimulate secretion of GH and PRL in cycling monkeys within a defined dose range, but that a decrease in pituitary responsiveness occurs at higher doses. One high dose of relaxin (2600 ng/kg.min) was infused for 1 h into the maternal and then the fetal circulations of chronically catheterized and tethered pregnant monkeys between 120-140 days gestation. Upon infusion of relaxin into the maternal circulation, there was a significant elevation of PRL in the mother but not the fetus. Upon infusion of relaxin into the fetus, there was no consistent change in PRL secretion in either the mother or the fetus. In conclusion, relaxin may have a heretofore undescribed role in pituitary physiology during the menstrual cycle and in pregnancy. SN - 0021-972X UR - https://www.unboundmedicine.com/medline/citation/2793997/The_effect_of_relaxin_infusion_on_prolactin_and_growth_hormone_secretion_in_monkeys_ L2 - https://academic.oup.com/jcem/article-lookup/doi/10.1210/jcem-69-5-956 DB - PRIME DP - Unbound Medicine ER -