Role of protein kinase C and phosphatases in the pulmonary vasculature of neonatal piglets

Objective: Persistent pulmonary hypertension of the newborn is characterize d by the presence of intense vasoconstriction and vascular remodeling. Prot ein tyrosine phosphorylation has been recognized as a critical regulatory e lement in signal transduction, because it is dynamically regulated by the o pposing actions of protein tyrosine kinases and protein tyrosine phosphatas es. The objectives of this study were to investigate the role of protein ki nase G and phosphatases in the neonatal pulmonary vasculature of normoxic a nd chronically hypoxic piglets. Design: Prospective, randomized, unblinded study. Setting: Hospital research laboratory. Subjects: Newborn Yorkshire-Landrace piglets. Interventions: Normoxic animals were 3-6 days old. Hypoxic animals were exp osed to hypoxia (Flo(2) 0.10) between 1 and 15 days of age to induce pulmon ary hypertension and then were studied. Measurements and Main Results: In isolated perfused lungs from normoxic pig lets, we measured the perfusion pressure to assess the vasoconstrictor resp onse to protein kinase G activation with phorbol 12,13-dibutyrate or 1-oley l-2-acetyl-glycerol. We also assessed the effect of protein kinase C inhibi tion with staurosporine (2 x 10(-6)M) and chelerythrine (5 x 10(-5)M) on en dothelin-1-induced pulmonary vasoconstriction. We then examined the effect of chelerythrine and phosphatase inhibition with phenylarsine oxide on the baseline perfusion pressure of normoxic and chronically hypoxic piglets. Ph orbol 12,13-dibutyrate and 1-oleyl-2-acetyl-glycerol caused a sustained, do se-dependent increase in perfusion pressure, with relative potencies about 100- and 1000-fold less than endothelin-1, respectively. Protein kinase G i nhibitors, chelerythrine and staurosporine, decreased the constrictor respo nse to endothelin-1. Chelerythrine did not affect baseline perfusion pressu re in the normoxic animal, whereas it lowered pulmonary vascular tone in ch ronically hypoxic animals. With respect to phosphatases, phenylarsine oxide significantly increased perfusion pressure in normoxia as well as in hypox ia. Conclusions: These findings confirm that protein kinase C activation causes sustained vasoconstriction in the neonatal pulmonary vasculature and media tes the vasoconstrictor action of potent peptides, like endothelin-1. These findings also confirm that protein kinase C activation could be induced by hypoxic exposure in the neonatal piglet pulmonary vasculature. Phosphatase s appear to modulate pulmonary vascular tone in the normoxic and hypoxic ne wborn piglet.