Osmoregulation of the magnocellular system during pregnancy and lactation

E. M. Koehler, G. L. McLemore, W. Tang, J. Y. Summy-Long

Research output: Contribution to journalArticle

Abstract

We compared the responsiveness of both the vasopressin (VP) and oxytocin (OT) magnocellular systems to osmotic stimulation during pregnancy and lactation to determine if changes in thresholds and sensitivities were similar for both neuropeptides. Virgin, pregnant (day 20), and lactating (day 6) Sprague-Dawley rats were injected with a hypertonic NaCl solution (0.25 M- 8.0 M NaCl; 15 ml/kg sc) and decapitated 2 h later. Late in gestation, the apparent osmotic threshold for both VP and OT release was lower by ~10 mosmol/kgH2O than that of virgin and lactating animals. The sensitivity (i.e., slope of the linear regression relating plasma osmolality and VP or OT levels) of the magnocellular system to osmoregulation, however, was unchanged in pregnant animals but was significantly attenuated (P <0.01) for both peptides during lactation (slopes of lactating vs. virgin rats: OT, 1.7 vs. 3.4; VP, 1.1 vs. 1.9). The neural lobe content of VP decreased (P <0.05) in pregnant rats, whereas OT stores were reduced (P <0.05) in lactating animals. Thus, during pregnancy, the lower tonicity of plasma is perceived as normal by both VP and OT neuroendocrine systems enabling excretion of an acute sodium or water load.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume264
Issue number3 33-3
StatePublished - 1993
Externally publishedYes

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Osmoregulation
Oxytocin
Vasopressins
Lactation
Pregnancy
Hypertonic Solutions
Posterior Pituitary Gland
Neurosecretory Systems
Neuropeptides
Osmolar Concentration
Sprague Dawley Rats
Linear Models
Sodium
Peptides
Water

Keywords

  • lactation
  • osmoregulation
  • oxytocin
  • pregnancy
  • vasopressin

ASJC Scopus subject areas

  • Physiology

Cite this

Osmoregulation of the magnocellular system during pregnancy and lactation. / Koehler, E. M.; McLemore, G. L.; Tang, W.; Summy-Long, J. Y.

In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 264, No. 3 33-3, 1993.

Research output: Contribution to journalArticle

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