The substrate-associated protein p45 of porcine endothelial cells: multiple isoforms, cytoskeletal-like properties and induction by hyperoxic stress.

1. Cultured mesenchymal cells respond to hyperoxic (hyper-O2) stress with increased cell flattening/substrate adhesion and overall 47-69% reductions in total matrix-associated (i.e. saponin-resistant [SAP fraction]) protein. 2. Electrophoretic analysis revealed a selective hyper-O2-related 2.7- to 4-fold increase in SAP and cytoskeletal fraction deposition of the protein p45 beginning early (within 12 hr) after initial exposure of porcine endothelial cells to hyper-O2 and increasing over a 48 hr period. 3. p45 consisted of 8 distinct isoforms differing only in pI; hyper-O2-augmented matrix deposition of 3. p45 consisted of 8 distinct isoforms differing only in pI; hyper-02-augmented matrix deposition of p45 involved all 8 isoforms with the more basic subtypes exhibiting slightly greater net increases. 4. Both the specificity and time course of p45 induction, relative to the onset of hyper-O2 cytoarchitectural remodeling, indicate that p45 up-regulation constitutes an early aspect of the hyper-O2 adaptive response.