Vascular Permeability to Hemorphins in the Central Nervous System

Blood-brain barrier (BBB) permeability to hemorphin-7, an endogenous morphine like peptide derived from haemoglobin, is unknown. The present investigation was undertaken to examine the microvascular permeability to 125I-labelled hemorphin-7 in different regions of the brain and spinal cord in normal male rats. In addition, the influence of hemorphin on brain water content and morphology of cerebral microvessels was examined at ultrastructural level. Rats received 1251-sodium instead of hemorphin served as controls. The BBB permeability to 1251-labelled hemorphin-7 was significantly higher in various brain and spinal cord regions at 3 min (35–70%) and 15 min (150–170%) after administration compared to 1251-sodium. On the other hand, the microvascular permeability to another form of hemorphin, Leu-Val-Val-hemorphin-7 was very close to that of radioactive iodine at both 3 or 15 min circulation period. Infusion of hemorphin-7 however, did not influence the regional brain water content or ultrastructure of the cerebral microvessels compared to either radioactive iodine or Leu-Val-Val-hemorphin-7. These results suggest that hemorphin-7 has the capacity to cross the BBB of normal rats without affecting brain edema formation or cerebrovascular ultrastructure.