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Neurohypophysial hormone receptors and second messengers in trout hepatocytes

M E Guibbolini1, P M Pierson, B Lahlou

  • 1Laboratoire de Physiologie Cellulaire et Moléculaire, CNRS UMR 6548, Université de Nice-Sophia Antipolis, Faculté des Sciences-Parc Valrose, 06108 Nice Cedex 2, France. guibboli@unice.fr

The Journal of Endocrinology
|October 6, 2000
PubMed

Insights

Trout hepatocytes possess neurohypophysial hormone receptors, specifically V(1a)-type, that regulate cyclic AMP production and calcium mobilization. These receptors are activated by arginine vasotocin and isotocin, influencing cellular signaling pathways.

Area of Science:

  • Comparative endocrinology
  • Fish physiology
  • Cell signaling

Background:

  • Neurohypophysial hormones play crucial roles in regulating physiological functions across vertebrates.
  • Understanding hormone receptor subtypes and their signaling mechanisms in fish is essential for comparative physiology.
  • Hepatocytes are key metabolic and signaling centers in fish, responding to various hormonal stimuli.

Purpose of the Study:

  • To characterize neurohypophysial hormone receptors in trout (Oncorhynchus mykiss) hepatocytes.
  • To investigate the involvement of second messengers, cyclic AMP (cAMP) and intracellular calcium (Ca2+), in the cellular response to these hormones.
  • To pharmacologically differentiate the receptor subtypes mediating these effects.

Main Methods:

  • Hepatocytes were treated with arginine vasotocin (AVT) and isotocin (IT) in the presence and absence of glucagon.
  • Cyclic AMP (cAMP) accumulation was measured to assess receptor-mediated signaling.
  • Intracellular calcium (Ca2+) levels were monitored using the fluorescent probe FURA-2/AM.
  • Specific V(1) and V(2) receptor agonists and antagonists were employed for pharmacological characterization.

Main Results:

  • AVT and IT inhibited glucagon-stimulated cAMP production in a concentration-dependent manner.
  • AVT also inhibited basal cAMP production, while IT did not.
  • AVT and IT induced a concentration-dependent increase in intracellular Ca2+.
  • Pharmacological analysis using V(1) and V(2) analogues indicated that the observed effects are mediated by V(1a)-type receptors.

Conclusions:

  • Trout hepatocytes possess neurohypophysial hormone receptors functionally similar to mammalian V(1a) receptors.
  • These receptors are linked to the inhibition of cAMP production and the mobilization of intracellular calcium.
  • The findings contribute to the understanding of neurohypophysial hormone action and receptor diversity in fish.

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