Failure of ductal closure is associated with an increase in mortality in very preterm infants.

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Preterm infants with volume- and pressor-resistant hypotension respond to hydrocortisone with rapid normalization of the cardiovascular status and sustained decreases in volume and pressor requirement.

EV is as accurate in measuring LVO as echocardiography and the variation in the agreement between EV and echocardiography among the individual subjects reflects the limitations of both techniques.

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We studied the effect of dopamine (DA) on Na+-K+-ATPase activity in proximal convoluted tubule (PCT) segments dissected from perfused rat kidneys. DA inhibited Na+-K+-ATPase activity in a dose-dependent manner. Inhibition was significant with 10(-7) M DA and maximal with 10(-4) M DA. The inhibition was reversible. Enzyme inhibition occurred in the presence of DA and a DA antagonist, metoclopramide, but not when 10(5) M of the DA1 and DA2 agonists fenoldopam mesylate and LY 171555 were added in the absence of DA. In PCT segments incubated with the DA precursor dopa, Na+-K+-ATPase activity was also inhibited. However, dopa did not inhibit the sodium pump if dopa decarboxylase activity was blocked with benserazide. These findings suggest an intracellular site of action of DA. In tubules incubated in different K concentrations, 10(-5) DA decreased the maximal activity (Vmax) and increased the Km. DA 10(-5) M caused an almost immediate swelling of PCT segments. Swelling did not occur in the presence of both DA and 10(-5) M amiloride. The DA-induced tubular swelling was probably due to inhibition of Na+-K+-ATPase-mediated Na+-transport. We conclude that in rat PCT segments, DA causes a rapid and reversible inhibition of apparent Na+-K+-ATPase activity and an apparent reduction in the affinity for K. The site of action appears to be intracellular.

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