Recently, a model of hypoxic damage was developed in the isolated, perfused rat liver (5). Perfusion with anoxic (95% N2, 5% CO2) buffer caused irreversible damage to virtually all hepatocytes in the liver lobule as evidenced by trypan blue uptake. In parallel with trypan blue staining, lactate dehydrogenase (LDH) release into the effluent per-fusate reached 2,000–3,000 U/L. The studies described here evaluate the effect of nitrendipine, a dihydropyridine-type calcium channel blocker, on hypoxic hepatocellular damage. Livers from fasted, female Sprague-Dawley rats were perfused for 10 min with normoxic (95% O2, 5% CO2) Krebs-Henseleit bicarbonate buffer. Subsequently, nitrendipine or ethanol vehicle was infused for 8 min in the presence of oxygen (0.2–20μM nitrendipine: final ethanol concentra-tion, 34 mM). Livers were then perfused for 50 min with nitrogen-saturated buffer. Identical experiments were performed using a Ca2+ -free perfusion medium. Within 20 min following the initiation of anoxic perfusion, LDH release reached 3,800 U/L in Ca2+ -containing medium and 1,800 U/L in Ca2+ -free medium. Trypan blue added at the end of the anoxic perfusion period (40 min) stained > 80% of the hepatocytes in all regions of the liver lobule both in the presence and absence of extracellular calcium. In livers pretreated with as little as 0.5 μM nitrendipine, LDH release into the perfusate at 20 and 30 min of perfusion was suppressed completely. Trypan blue uptake measured following 50 min of hypoxia was reduced half-maximally by 5–10 μM nitrendipine. Scanning electron microscopy demonstrated hepatocellular bleb formation after 10 min of hypoxia cell fragmentation in 30 min. These were prevented by 1 μM nitrendipine. Nitrendipine provided protection against hepatocellular damage both in the presence and absence of extracellular calcium. Taken together, these data indicate that nitrendipine is a useful protective drug in livers when hypoxia is involved in the mechanism of damage. It may be therapeutic in alcoholic liver disease, in prevention of chemical and drug injury, and in preservation of livers for transplantation.
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