Angiotensin II regulates tyrosine hydroxylase activity and mRNA expression in rat mediobasal hypothalamic cultures: The role of specific protein kinases

Frank Y. Ma, David R. Grattan, Larisa Bobrovskaya, Peter R. Dunkley, Stephen J. Bunn

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Abstract

Dopamine secreted by hypothalamic neurons is crucial in regulating prolactin secretion from the pituitary. We have examined the ability of angiotensin II (AngII) to regulate the activity of these dopaminergic neurons and thus act as a potential physiological regulator of prolactin secretion. Using a hypothalamic cell culture preparation we determined the effect of Angll on tyrosine hydroxylase activity and expression (TOH). This is important because TOH is the rate-limiting enzyme in dopamine biosynthesis. Angll stimulated a time- and concentration-dependent increase in TOH activity which was suppressed by inhibitors able to act on protein kinase A (PKA), protein kinase C (PKC) and Ca2+/calmodulin-dependent protein kinase II (CaMPKII). An inhibitor of the mitogen-activated protein kinase (MAPK) pathway, PD 98059, reduced basal TOH activity but the AngII response was still detectable. AngII stimulation enhanced the phosphorylation of TOH at Ser19, Ser31 and Ser40. AngII also induced a time-dependent increase in TOH mRNA expression which was unaffected by inhibitors able to act on PKA and CaMPKII, but was abolished by inhibitors able to act on ERK and PKC. AngII responses were very much larger in cultures prepared from female when compared to male rat pups. Data from adult hypothalamic slices confirmed this sexual dimorphism and supported the role of the protein kinases noted above. Therefore AngII can regulate both the activity and expression of TOH in hypothalamic neurons employing multiple, but only partially overlapping, signaling pathways.

Original languageEnglish
Pages (from-to)431-441
Number of pages11
JournalJournal of Neurochemistry
Volume90
Issue number2
DOIs
Publication statusPublished - 1 Jul 2004
Externally publishedYes

Keywords

  • Angiotensin II
  • Dopaminergic hypothalamic neurons
  • Prolactin
  • Protein kinases
  • Tyrosine hydroxylase

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