Intracellular calcium in the isolated rat liver: correlation to glucose release, K(+) balance and bile flow.
This study correlates whole organ measurements of intracellular calcium concentration ([Ca(2+)](i)) with hormone-induced (epinephrine, vasopressin) changes of liver functions (glucose release, K(+) balance and bile flow). [Ca(2+)](i) was measured in the isolated perfused rat liver using the sensor Fura-2 and applying liver surface fluorescence spectroscopy. The technique was improved by (i) minimizing biliary elimination of the sensor by employing a rat strain deficient in canalicular organic anion transport (TR(-) mutation) and (ii) by correcting for changes of interfering intrinsic organ fluorescence that was shown to depend on the oxidation-reduction state (NAD(P)H content) of the organ. Epinephrine (50 nM) elicits an instantaneous peak rise of [Ca(2+)](i) to approx. 400 nM, followed by a sustained elevation that depends on the presence of extracellular Ca(2+). The rise of [Ca(2+)](i) coincides with initiation of glucose release, transient K(+) uptake, and transient stimulation of bile flow. Vasopressin (2 nM) exerts qualitatively similar effects. The transient rise of bile flow is attributed to Ca(2+)-mediated contraction of the pericanalicular actin-myosin web of hepatocytes.
Wurzinger
R
R
Department of Pathophysiology, University of Vienna, Austria.
Englisch
R
R
Roka
S
S
Langer
R
R
Roden
M
M
Graf
J
J
D000818:Animals; D001646:Bile / Q000378:metabolism*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002614:Chelating Agents / Q000737:chemistry; D004837:Epinephrine / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000737:chemistry; D016257:Fura-2 / Q000737:chemistry; D005947:Glucose / Q000378:metabolism*; D008099:Liver / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000172:deficiency / Q000235:genetics; D009154:Mutation; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D051381:Rats / Q000235:genetics; D017208:Rats, Wistar; D014667:Vasopressins / Q000494:pharmacology
D002118:Calcium; D002614:Chelating Agents; D004837:Epinephrine; D005456:Fluorescent Dyes; D016257:Fura-2; D005947:Glucose; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011188:Potassium; D014667:Vasopressins; C421109:multidrug resistance-associated protein 1