Modulatory effect of blood cells on hypoxic vasoconstriction response and nitric oxide release in rat lungs

In this study, we investigated the modulatory effects of different types of blood cells on hypoxic pulmonary vasoconstrictive (HPV) response and nitri c oxide (NO) release in isolated rat lungs. The lungs were perfused at a co nstant flow with physiologic saline solution (PSS). The changes in pulmonar y arterial pressure (PAP) and NO release were observed. Two hypoxic challen ges with a 5% CO2-95% N-2 gas mixture were carried out in each experiment. Hypoxia induced pulmonary vasoconstriction, as reflected by an increase in PAP (0.88 +/- 0.22 cmH(2)O). At the same time, NO (342.9 +/- 78.3 my) relea se from the lungs Tvas also increased. Addition of white blood cells (WBCs, 0.70 to 0.88 x 10(5)/mL), platelets (1.48 to 1.96 x 10(5)/mL), or red bloo d cells (RBCs, 4.6 to 6.6 x 10(5)/mL) into the perfusate produced different effects on PAP and NO changes. WBCs decreased the pulmonary vasoconstricti on response and this was accompanied hy an increase in NO release. Platelet s had no significant effects on either PAP or NO. RBCs significantly potent iated the PAP increase and attenuated the NO release. The results indicate that NO release during hypoxia tends to offset pulmonary vasoconstriction a nd that NO release and HPV response are modulated by different cell element s.