ALTERED HEPATOCELLULAR CA2-SHOCK AND RESUSCITATION( REGULATION DURINGHEMORRHAGIC)

The present study evaluated the effect of the benzothiazepine Ca2+ cha nnel blocker diltiazem (DZ) on altered hepatocellular Ca2+ regulation and oxidant injury during hemorrhagic shock/resuscitation. In anesthet ized, male Sprague-Dawley rats, hemorrhagic shock was induced by rapid blood withdrawal and maintaining the mean arterial blood pressure at 40 mm Hg over 60 minutes, Rats were then resuscitated with 60% of shed blood and threefold the shed blood volume of Ringer's lactate. At the end of ischemia, and 60 or 300 minutes after resuscitation, hepatocyt es were isolated by liver collagenase perfusion, Hepatocellular Ca2+ e xchange (Ca-ex(2+)), rate of cellular Ca2+ influx (Ca-in(2+)), and Ca2 + membrane flux (Ca-flux(2+),) were determined using Ca-45 incubation techniques, Hepatocyte oxidant injury was evaluated by fluorometricall y measuring thiobarbituric acid reactive substances and oxidized/reduc ed glutathione, Both hemorrhage and hemorrhage/resuscitation increased hepatocellular Ca-in(2+), Ca-ex(2+), and Ca-flux(2+). In contrast to control and sham-operated rats, in vitro stimulation by the Ca2+ agoni st epinephrine (100 nmol/L) of hepatocytes from either hemorrhaged or resuscitated rats did not further increase Ca-in(2+), Administration o f DZ (.8 mg/kg) with resuscitation significantly decreased cellular Ca -ex(2+) and Ca-flux(2+), but did not restore impaired epinephrine-indu ced Ca-in(2+). DZ prevented hepatocyte Lipid peroxidation and glutathi one oxidation, These findings suggest hepatocellular Ca2+ overload and impaired Ca2+ signaling during hemorrhage/resuscitation. Increased Ca 2+ uptake could be because of a receptor-gated Ca2+ influx and/or oxyg en-free radical induced membrane Ca2+ leaks.