ATP-MGCL2 TREATMENT AFTER TRAUMA-HEMORRHAGE RESUSCITATION INCREASES HEPATOCYTE P-2-PURINOCEPTOR BINDING-CAPACITY

Although our studies indicate that P-2-purinoceptor binding capacity d ecreases after hemorrhage and resuscitation, it is not known whether A TP-MgCl2 administration after hemorrhage has any beneficial effects on the receptor dynamics. To study this, we performed laparotomy (i.e., trauma induced) on rats and bled them to and maintained them at a mean arterial pressure of 40 mmHg until 40% of maximum bleedout volume was returned in the form of Ringer lactate (RL). The animals were then re suscitated with 3 times the volume of maximum bleedout with RL over 45 min followed by 2 times RL along with ATP-MgCl2 (50 mu mol/kg body wt ) over 95 min. Hepatocytes were isolated at 4, 17, and 27 h after resu scitation. P-2-purinoceptor binding characteristics were determined by using [alpha-S-35]ATP. Scatchard analysis revealed high-affinity and low-affinity receptor components in the hepatocytes isolated from sham -operated or hemorrhaged animals with or without ATP-MgCl2 infusion. A TP-MgCl2 ameliorated and subsequently restored the decreased maximum b inding capacity (B-max) of the high-affinity receptor component and si gnificantly improved B-max of the low-affinity receptor component. ATP -MgCl2 administration also produced a progressive enhancement in the a ffinity of the low-affinity receptor component. Thus the beneficial ef fects of ATP-MgCl2 observed after trauma-hemorrhage and resuscitation may be, in part, due to the restoration of P-2-purinoceptor binding ca pacity and the enhancement of the receptor affinity.