The role of cerebral microvessels in the elimination of histamine released during postasphyxial reperfusion in newborn piglets

Abstract

Histamine, released from intracerebral sources during hypoxic-ischemic conditions, may take part in the pathogenesis of neonatal brain injuries. In order to elucidate the possible role of cerebral microvessels in the elimination of histamine from the extracellular space, we determined the concentration of histamine using a modified radioenzymatic method in plasma taken from the internal jugular vein, in cerebrospinal fluid, and in capillary-rich fraction of cerebral microvessels prepared from cortex in 12 sham-operated piglets. Then, bilateral pneumothorax was induced in 20 piglets, samples were taken from the same compartments as from the controls before and during asphyxia, as well as 15 and 180 min thereafter, respectively. Plasma histamine level was significantly ( P < 0.05) elevated in animals during hypoxic cardiovascular and metabolic failure (13.5 ± 1.9 nM l −1) compared to the value measured in the control group (2.2 ± 0.5 nM l −1), preceding any detectable change of histamine concentration in cerebrospinal fluid (5.2 ± 1.9 versus 3.8 ± 1.1 nM l −1, respectively) or in cerebral microvessels (8.4 ± 0.8 versus 7.1 ± 0.6 pM (mg protein) −1). After resuscitation, histamine levels in plasma samples remained high during the early (15 min, 16.2 ± 4.3 nM × l −1) and late (180 min, 15.3 ± 2.9 nM l −1) reperfusion period. By contrast, histamine concentration was increased considerably ( P < 0.05) in cerebrospinal fluid samples obtained 15 min (12.8 ± 6.5 nM l −1), but not 180 min (5.2 ± 1.9 nM l −1) after resuscitation. Significant ( P < 0.05) elevation of histamine concentration was seen only in cerebral microvessels prepared from asphyxiated piglets 180 min after resuscitation (18.6 ± 5.3 versus 7.2 ± 1.6 pM (mg protein) −1). We conclude that cerebral microvessels may take part in the elimination of histamine from the extracellular space during recovery of asphyxia in newborn pigs.