Changes in brain neurofilament and beta-tubulin proteins after cerebral hypoxia-ischemia in rabbits

Neurofilaments (NF) and tubulin are highly phosphorylated proteins that are important in neuronal structure and function. Changes in phosphorylation alter their antigenicity, and previous studies examining the effect of ischemia on these proteins failed to consider this factor. Using phosphate-independent antibodies and a quantitative immunoassay, we examined whether the amount of NF 68-kD (NF 68), NF 160-kD (NF 160), NF 200-kD (NF 200) and class III beta-tubulin proteins in the brain are reduced after cerebral injury. Rabbits were subjected to 8 min of hypoxia and then to 8 min of ischemia. After 4 h of reperfusion, NF 68 decreased from an overall group mean (+/- SEM) of 17.5+/-2.3 ng NF 68 microg/total protein in the noninjured controls (n = 8) to 12.9+/-1.2 ng/microg total protein in the hypoxic-ischemic group (n = 9). Conversely, NF 200 increased from 31.6+/-3.3 ng/microg in controls to 47.7+/-3.2 ng/microg. The amount of NF 160 and beta-tubulin was unchanged. The response of the NF proteins to brain injury is more complicated than described previously. Additional studies examining the regulation and metabolism of the NF are warranted, especially regarding the role of phosphorylation.