Objective: To study the effects of poly-adenosine diphosphate ribosyl-polymerase (PARP) on vascular hyporeactivity during hemorrhagic shock in rats.
Methods: Sprague-Dawley (SD) rats were randomly divided into three groups: shock, 3-aminobenzamide (3-AB) pretreatment+shock, and sham operation. Bleeding from the femoral artery to induce hemorrhagic shock model. The blood pressure changes following 3 microg/kg norepinephrine (NE) injection were observed in vivo. The response of vascular rings of superior mesenteric artery (SMA) to NE was determined ex vivo. The nitrogen monoxide (NO) contents of plasma and tissue homogenate of SMA were measured using the assay kit based on the nitrate reductase reaction.
Results: The maximum increase of mean arterial pressure in response to NE immediately following shock in the shock group was significantly lower than in the sham operation group (P<0.01) and the value at 1 hour after blood reinfusion in the shock group was obviously lower than in the 3-AB pretreatment+shock group (P<0.05) and in the sham operation group (P<0.01). The maximum concentration force in the sham operation group [(0.367 1+/-0.221 3)g/mm] was significantly increased than in the 3-AB pretreatment+shock group [(0.286 4+/-0.153 2) g/mm, P<0.05] and in the shock group [(0.185 6+/-0.111 3)g/mm, P<0.01]. The cumulative dose-response curves of SMA to NE shifted to the left, and the contraction force was markedly increased as NE concentration reaching 10(-6), 10(2+) and 10(-5) mol/L in the 3-AB pretreatment+shock group compared to the shock group (all P<0.05). There were no significant difference on plasma NO content among the three groups. However, the NO contents of plasma and tissue homogenate of SMA in the 3-AB pretreatment+ shock group were slightly lower than in the shock group (P>0.05).
Conclusion: PARP is involved in the vascular hyporeactivity in hemorrhagic-shocked rats.