Although our studies indicate that P2-purinoceptor binding capacity decreases after hemorrhage and resuscitation, it is not known whether ATP- MgCl2administration 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 resuscitated with 3 times the volume of maximum bleedout with RL over 45 min followed by 2 times RL along with ATP-MgCl2(50 μmol/kg body wt) over 95 min. Hepatocytes were isolated at 4, 17, and 27 h after resuscitation. P2-purinoceptor binding characteristics were determined by using [α-35S]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-MgCl2infusion. ATP-MgCl2ameliorated and subsequently restored the decreased maximum binding capacity (B(max)) of the high-affinity receptor component and significantly improved B(max) of the low-affinity receptor component. ATP-MgCl2administration also produced a progressive enhancement in the affinity of the low-affinity receptor component. Thus the beneficial effects of ATP-MgCl2observed after trauma-hemorrhage and resuscitation may be, in part, due to the restoration of P2-purinoceptor binding capacity and the enhancement of the receptor affinity.