Objective: To compare the vasoactive effects of dopamine (DOPA) of different concentrations on isolated rabbit pulmonary and systemic arteries after incubation with lipopolysaccharide (LPS).
Methods: Six white male rabbits were used. Thirty-six pulmonary arterial rings and 36 systemic arterial rings were prepared. The 36 pulmonary arterial rings were divided into six groups to determine the effect of different concentrations of DOPA (4x10(-5) , 8x10(-5), 16x10(-5) micromol/L) on the tension of the normal pulmonary artery (PN-DOPA4, PN-DOPA8, PN-DOPA16 groups, respectively), and the tension of the pulmonary artery rings after being incubated with LPS (PL-DOPA4, PL-DOPA8, PL-DOPA16 groups, respectively). The 36 systemic arterial rings were also divided into six groups as the pulmonary arterial rings, including normal groups (SN-DOPA4, SN-DOPA8 , SN-DOPA16) and LPS groups (SL-DOPA4, SL-DOPA8 , SL-DOPA16).
Results: (1) DOPA relaxed the arterial rings in PN-DOPA4 and SN-DOPA4 groups, while it produced contraction in PN-DOPA8, PN-DOPA16, SN-DOPA8 and SN-DOPA16 groups, and the contraction was more marked with the increase in concentration of DOPA. (2) After preincubation with LPS, the relaxation property of DOPA in PL-DOPA4 and SL-DOPA4 groups was observed to be reversed to contraction [(22.60+/-6.68)% vs. -(2.25+/-0.58)%, (3.80+/-0.52)% vs. -(3.65+/-0.75)%, P<0.05 and P<0.01]; the contraction response of DOPA in PL-DOPA8 group decreased compared with PN-DOPA8 group by (14.52+/-0.59)% (P<0.05), while increased by (25.90+/-1.75)% in SL-DOPA8 group compared with SN-DOPA8 group (P<0.05), and no response was observed in PL-DOPA16 and SL-DOPA16 groups. (3)After preincubation with LPS, changes in pulmonary arterial tension (PL/PN) in DOPA4 group were more obvious than those in systemic arterial tension (SL/SN, -10.90+/-5.06 vs. -1.00+/-0.24, P<0.05), while the SL/SN in DOPA8 group were more obvious (1.80+/-0.35 vs. 0.48+/-0.17, P<0.01).
Conclusion: DOPA in low concentrations had the function of relaxation on the pulmonary arterial and systemic arterial rings. After the arterial rings are preincubated with LPS, the relaxation response of DOPA of low concentrations is changed to be vaso-contraction, and the changes in pulmonary arterial rings are most marked. DOPA of different concentrations all produce contraction effect on LPS-preincubated arterial rings.