Effects of metabolic levels of PKC isofOrms inhibition ' on phosphorylation in the guinea pig taenia caeci

We investigated which isoform of protein kinase C (PKC) is responsible to metabolic inhibition i the guinea pig taenia caeci with respect to their phosphorylation levels. By Western blot analysis using isoform-specific antibodies, at least four isoforms of PKC, ct, 62, E and C were identified in the taenia. Prolonged metabolic inhibitlon of hypoxia, hypoxia+glucose depletion, and addition of cyanide (all in the presence of high K') for more than 60 min, but not glucose-depletion only, elicited dephosphorylation of PKCs, a, t]2 and E, except g. Ca2' depletion from the medium prevented the dephosphorylation of PKCs inducecl by hypoxia, and apparentiy inhibited the dephosphorylation induced by hypoxia+glucose depletion. Acute treatment with hypoxia for 10-30 min elicited a gradual dephosphorylation of PKCt32, but not of other tested PKC isoforms, Considering the ATP level under various metabolic conditions reported previously, PKCfi2 is suggested to be primarily responsible to hypoxia, and its dephosphorylation s closely associated with the alteration of adenylate compounds in the cell. Re-oxygenation after prolonged hypoxia did not restore the phesphoryation level of any tested PKCs, suggesting that the clephosphorylation of PKCs is asseciated with the irreversible damage of the cell under hypoxia. Presumably, the dephosphorylaton of PKCs, particularly PKCfi2, plays a role in the signal transduction pathway under metabolic inhibitien of the taenia, as reported in proliferative ancl pathephysiological processes in