Effect of hyperphenylalaninemia chemically induced on in vitro incorporation of P-32 into cytoskeletal proteins from cerebral cortex of developing rats

We studied the effect of hyperphenylalaninemia on in vitro incorporation of P-32 into cytoskeletal proteins from cerebral cortex of rats by injecting L-phenylalanine plus alpha-methylphenylalanine subcutaneously from the 6th to the 14th day postpartum. Chronic hyperphenylalaninemia induced an increased in vitro phosphorylation of the 150-kDa neurofilament subunit and tubulins present in the cytoskeletal fraction at the end of the treatment and 3 days after treatment discontinuation. In addition, when in vitro phosphorylation of the cytoskeletal proteins from treated animals was performed in the presence of the drugs we observed a decreased in vitro incorporation of P-32 into these proteins. Thus, the effect of L-phenylalanine plus alpha-methylphenylalanine on the endogenous protein kinase and phosphatase activities was examined and the results demonstrated that these drugs have an inhibitory effect on calcium/calmodulin-dependent protein kinase II and protein phosphatase type 1. (C) 1997 Academic Press.