ROUTES OF EXCRETION OF NEURONAL LYSOSOMAL DENSE BODIES AFTER VENTRICULAR INFUSION OF LEUPEPTIN IN THE RAT - A STUDY USING UBIQUITIN AND PGP9.5 IMMUNOCYTOCHEMISTRY
Jb. Cavanagh et al., ROUTES OF EXCRETION OF NEURONAL LYSOSOMAL DENSE BODIES AFTER VENTRICULAR INFUSION OF LEUPEPTIN IN THE RAT - A STUDY USING UBIQUITIN AND PGP9.5 IMMUNOCYTOCHEMISTRY, Journal of neurocytology, 22(9), 1993, pp. 779-791
To determine the rate and routes of removal of lysosomal, lipofuscin-l
ike dense bodies from neurons, the protease inhibitor, leupeptin, was
infused into the lateral ventricle of rats for up to nine days. After
seven days a number of animals were then allowed to recover. The forma
tion and later disappearance of dense bodies was followed by morpholog
y and immunocytochemistry, After 48 h of infusion lysosomal dense bodi
es in large numbers appeared in cortical, hippocampal and cerebellar n
eurons, which also showed increased ubiquitin immunoreactivity, as wel
l as in other cell types. By 3-4 days ubiquitin-immunoreactive dense b
odies were equally distributed between neurons and astroglia. After se
ven to nine days of infusion ubiquitin immunoreactive dense bodies fil
led neuronal perikarya, dendrites and expanded initial segments of man
y axons and were abundant in glial processes. All dense bodies studied
by electron microscopy were ubiquitin immunoreactive. After four days
of recovery dense bodies were markedly fewer in neuronal perikarya, a
nd virtually all were now within glial processes. From 7 to 28 days of
recovery, when most neurons appeared normal, lipofuscin bodies remain
ed in axon initial segments and in reduced numbers in glial processes,
particularly around blood vessels and beneath the pia of hippocampus
and of cerebellar cortex. Thus, neurons probably have a steady passage
of short lived proteins through the lysosomal excretory pathway. The
observed temporal sequence of events on recovery suggests that seconda
ry lysosomes probably pass rapidly from neuronal perikarya and dendrit
es to astrocytes and thus to the vascular bed or pia-arachnoid. The me
chanism of cell-to-cell transfer is not clear from this study.