CHANGES OF ACTIVITY AND ULTRASTRUCTURAL-LOCALIZATION OF ALKALINE-PHOSPHATASE IN CEREBRAL CORTICAL MICROVESSELS OF RAT AFTER SINGLE INTRAPERITONEAL ADMINISTRATION OF MERCURIC-CHLORIDE
J. Albrecht et al., CHANGES OF ACTIVITY AND ULTRASTRUCTURAL-LOCALIZATION OF ALKALINE-PHOSPHATASE IN CEREBRAL CORTICAL MICROVESSELS OF RAT AFTER SINGLE INTRAPERITONEAL ADMINISTRATION OF MERCURIC-CHLORIDE, Neurotoxicology, 15(4), 1994, pp. 897-902
Inorganic mercury salts administered systemically at low mg/ml doses p
roduce neurotoxic effects without penetrating the cerebral microvascul
ar endothelial cells which form the blood-brain barrier (BBB). This ph
enomenon promoted investigations testing a hypothesis relating inorgan
ic mercury-induced brain dysfunction to its interference with the BBB
transport. In the present study, we tested the effect of a single i.p.
administration of mercuric chloride (MC) (6 mg/kg body weight) on the
activity and ultrastructural localization of cerebral alkaline phosph
atase (AP), a cerebromicrovascular marker enzyme primarily located on
luminal plasmalemma of endothelial cells. At 1h after MC administratio
n, light microscopy revealed a virtual absence of AP in cerebral corti
cal layers II and III, and its dramatic reduction in the remaining lay
ers. Electron microscopy confirmed the disappearance of the AP reactio
n product from luminal endothelial cell membranes, and luminal phasmal
emma revealed pinocytic vesicles and invaginations likely to manifest
changes in BBB transport At 18h posttreatment, a moderate enzyme activ
ity appeared on abluminal endothelial plasmalemma and on basement memb
rane, but remained absent from luminal plasmalemma. A similar picture
persisted through day 5 post-treatment. The inhibition and subsequent
translocation of AP activity from luminal to abluminal site and the ac
companying ultrastructural changes are typical of the formation of ''l
eaky'' microvessels, previously reported for a variety of neuropatholo
gical conditions associated with BBB damage. (C) 1994 Intox Press, Inc
.