The effect of bile salts and calcium on isolated rat liver mitochondria.
Intact mitochondria were incubated with and without calcium in solutions of chenodeoxycholate, ursodeoxycholate, or their conjugates. Glutamate dehydrogenase, protein and phospholipid release were measured. Alterations in membrane and organelle structure were investigated by electron paramagnetic resonance spectroscopy. Chenodeoxycholate enhanced enzyme liberation, solubilized protein and phospholipid, and increased protein spin label mobility and the polarity of the hydrophobic membrane interior, whereas ursodeoxycholate and its conjugates did not damage mitochondria. Preincubation with ursodeoxycholate or its conjugate tauroursodeoxycholate for 20 min partially prevented damage by chenodeoxycholate. Extended preincubation even with 1 mM ursodeoxycholate could no longer prevent structural damage. Calcium (from 0.01 mM upward) augmented the damaging effect of chenodeoxycholate (0.15-0.5 mM). The combined action of 0.01 mM calcium and 0.15 mM chenodeoxycholate was reversed by ursodeoxycholate only, not by its conjugates tauroursodeoxycholate and glycoursodeoxycholate. In conclusion, ursodeoxycholate partially prevents chenodeoxycholate-induced glutamate dehydrogenase release from liver cell mitochondria by membrane stabilization. This holds for shorter times and at concentrations below 0.5 mM only, indicating that the different constitution of protein-rich mitochondrial membranes does not allow optimal stabilization such as has been seen in phospholipid- and cholesterol-rich hepatocyte cell membranes, investigated previously.
Güldütuna
S
S
Medical Clinic II, Department of Gastroenterology, Center of Internal Medicine, Johann Wolfgang Goethe-University, Theodor-Stern-Kai 7, D-60590, Frankfurt, Germany.
Zimmer
G
G
Leuschner
M
M
Bhatti
S
S
Elze
A
A
Deisinger
B
B
Hofmann
M
M
Leuschner
U
U
D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D002635:Chenodeoxycholic Acid / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects*; D010743:Phospholipids / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013113:Spin Labels; D014580:Ursodeoxycholic Acid / Q000494:pharmacology
D001647:Bile Acids and Salts; D010743:Phospholipids; D011506:Proteins; D013113:Spin Labels; D002635:Chenodeoxycholic Acid; D014580:Ursodeoxycholic Acid; D005969:Glutamate Dehydrogenase; D002118:Calcium