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First published online on June 7, 2004.
Experimental Physiology (2004)
DOI: 10.1113/expphysiol.2004.027243
© The Physiological Society 2004
A more recent version of this article appeared on September 1, 2004
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Received January 15, 2004
Revised March 2, 2004
Accepted after revision May 24, 2004

Neuroendocrinology/endocrinology

Interaction of Prolactin, ANPergic, oxytocinergic, and adrenal systems in response to extracellular volume expansion in male Wistar rats

Flavia V Durlo 1, Margaret Castro 2*, Lucila LK Elias 2, Jose Antunes-Rodrigues 2

1 Universidade de Campinas
2 Faculdade de Medicina de Ribeirao Preto

* To whom correspondence should be addressed. E-mail: castrom{at}fmrp.usp.br.


  Abstract
The present study evaluated the effect of acute extracellular volume expansion (EVE) by intravenous injection of isotonic (0.15M NaCl) or hypertonic (0.3M NaCl) saline on the prolactin, corticosterone, vasopressin, oxytocin, and atrial natriuretic peptide secretion. Wistar male rats were submitted to different experimental manipulations: control group, and animals treated with bromocriptine, sulpiride or dexamethasone. After isotonic and hypertonic EVE, the control group showed a significant increase in prolactin, corticosterone, atrial natriuretic peptide and oxytocin plasma concentrations. The increase of atrial natriuretic peptide and oxytocin levels in response to hypertonic EVE was more pronounced than with isotonic EVE. Bromocriptine and sulpiride treatments did not modify corticosterone, atrial natriuretic peptide and oxytocin responses to either isotonic or hypertonic EVE. The increases in prolactin and oxytocin, but not atrial natriuretic peptide were blocked in dexamethasone pretreated rats. In conclusion, isotonic or hypertonic EVE induced an increase in prolactin, corticosterone, atrial natriuretic peptide and oxytocin plasma concentrations. The increases in atrial natriuretic peptide and oxytocin were independent of prolactin plasma concentrations. The increases in prolactin and oxytocin were blocked by the inhibition of the hypothalamo-pituitary-adrenal (HPA) axis by dexamethasone. However, dexamethasone did not alter the increase in atrial natriuretic peptide secretion induced by isotonic or hypertonic EVE. Therefore, prolactin might participate in the regulation of the hydroelectrolytic balance in mammals; however, in this protocol, there is no evidence for direct interaction with ANPergic and oxytocinergic systems. Additionally, the response of the prolactin and oxytocin induced by isotonic or hypertonic EVE is modulated by the HPA axis.

Key Words: Natriuretic peptide, Oxytocin, Prolactin






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