Effect of catecholamines on activity of Na(+), K(+)-ATPase in neonatal piglet brain during posthypoxic reoxygenation.

The present study examined the possible role of dopamine on the response of Na(+), K(+)-ATPase activity in the striatum of newborn piglets to 1 h of bilateral carotid ligation with hemorrhage and 2 h of recovery. Newborn piglets, 2-4 days of age and with and without prior treatment with alpha-methyl-p-tyrosine (AMT), an inhibitor of catecholamines synthesis, were used for the study. The oxygen pressure in the microvasculature of the cortex (PcO(2)) was measured by oxygen dependent quenching of the phosphorescence. In sham-operated animals the PcO(2) was 50+/-3 torr. Following ligation and hemorrhage the PcO(2) decreased to 8+/-0.5 torr. After release of ligation and reperfusion PcO(2) increased to 45+/-4 torr, a value not significantly different from controls, in approximately 30 min. There were no significant differences in PcO(2) between AMT treated and untreated animals. In sham-operated animals striatal Na(+),K(+)-ATPase was 29.1+/-3 micromol/mg protein per h and decreased by 25% after 2 h of recovery. Depleting the brain of catecholamines prior to ligation and hemorrhage abolished this decrease. It is postulated that the decrease in the level of dopamine in the brain prior to ligation and hemorrhage can be at least partly responsible for the observed decrease in activity of Na(+), K(+)-ATPase in the striatum of newborn piglets.