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expression and decrease of PKA activity
Departments of 1 Internal Medicine and 2 Medical Physiology, 3 Division of Research and Education, Scott & White Hospital, Texas A&M University System Health Sciences Center, College of Medicine, and 4 Central Texas Veterans Health Care System, Temple, Texas 76504; 5 Department of Internal Medicine, Tohoku University School of Medicine, Aobaku, Sendai, Japan 980-8574; 6 Division of Gastroenterology, University of Rome, La Sapienza, Rome, Italy 00100; 7 Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas, and 8 Department of Morphology and Molecular Pathology, University of Leuven, 3000 Leuven, Belgium
To determine the role and
mechanisms of action by which dopaminergic innervation modulates ductal
secretion in bile duct-ligated rats, we determined the expression of
D1, D2, and D3 dopaminergic receptors in cholangiocytes. We evaluated
whether D1, D2 (quinelorane), or D3 dopaminergic receptor agonists
influence basal and secretin-stimulated choleresis and lumen expansion
in intrahepatic bile duct units (IBDU) and cAMP levels in
cholangiocytes in the absence or presence of BAPTA-AM,
chelerythrine, 1-(5-isoquinolinylsulfonyl)-2-methyl piperazine
(H7), or rottlerin. We evaluated whether 1)
quinelorane effects on ductal secretion were associated with increased
expression of Ca2+-dependent PKC isoforms and
2) increased expression of PKC causes inhibition of PKA
activity. Quinelorane inhibited secretin-stimulated choleresis in
vivo and IBDU lumen space, cAMP levels, and PKA activity in
cholangiocytes. The inhibitory effects of quinelorane on
secretin-stimulated ductal secretion and PKA activity were blocked by
BAPTA-AM, chelerythrine, and H7. Quinelorane effects on ductal
secretion were associated with activation of the
Ca2+-dependent PKC-
but not other PKC isoforms. The
dopaminergic nervous system counterregulates secretin-stimulated ductal
secretion in experimental cholestasis.
intrahepatic biliary epithelium; bile flow; secretin receptor
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