POSTISCHEMIC CHANGES IN PROTEIN-KINASE-C RNA IN THE GERBIL BRAIN FOLLOWING PROLONGED PERIODS OF RECIRCULATION - A PHOSPHORIMAGING STUDY

Northern blot analysis was performed to investigate the long-term chan ges in mRNA expression of protein kinase C (PKC) in the gerbil brain f ollowing transient cerebral ischemia. We have previously demonstrated an increase in mRNA levels of certain Ca2+ independent forms of PKC in early recirculation periods i.e., 6 h and 24 h postischemia (PI). But , since neuronal death in susceptible regions usually occurs 2-3 days following ischemia, this study examined the mRNA levels of PKC after p rolonged periods of reperfusion following ischemia. The mRNA expressio n was also examined at an early recirculation period, i.e., 1 h, to de termine how early the alterations begin to occur. Global forebrain isc hemia was produced in gerbils by 10 min of bilateral carotid artery oc clusion. RNA was prepared from forebrains of nonischemic controls and PI animals following 1 h, 3 d, and 7 d of recirculation (n=3 to 4 in e ach group) and hybridized with synthetic oligonucleotide probes for PK C, delta, epsilon, and zeta based on cDNA sequences in rat and labelle d with P-32. The autoradiographs were recorded and quantified by a sen sitive system, Phosphor Imager, followed by conventional x-ray film ex posure. The mRNA levels of all 3 PKC isozymes examined were found to b e elevated as early as 1 h recirculation following ischemia. The incre ases in mRNA levels of both delta PKC following 6 h and 24 h of recirc ulation as well as that of zeta PKC following 24 h of recirculation, a s reported earlier, return to control levels by 3 d PI and remain at t hat level 7 d PI. The changes in mRNA expression of PKC epsilon tended to follow a similar course, but there were wide variations within eac h group. These data suggest that PKC may have important roles in the p athophysiology of ischemic neuronal injury starting early during the i nitial periods of reperfusion and continuing until the appearance of d elayed neuronal death.