title: Extracellular matrix changes PC12 cell shape and processing of newly synthesized dopamine.
abstract: PC12 cells on extracellular matrix (ECM) or plastic were incubated with 3H-tyrosine (3H-TY) in the presence and absence of serum or cold tyrosine. 3H-Dopamine (3H-DA) was determined in medium and cells from 1 to 48 h later with Dowex cation exchange chromatography. In serum-free and tyrosine-free medium, PC12 cells on ECM released significantly more 3H-DA, whereas cells on plastic had a significantly higher cellular content of 3H-DA, but total 3H-DA (medium plus cells) was equal in ECM and plastic cultures. When 3H-TY was added to tyrosine-containing medium, there was a significant decrease in the levels of 3H-DA detected and the differences between ECM and plastic cultures were attenuated, but the patterns of secretion and storage were similar to those observed with tyrosine-free medium and total synthesis did not decline at 48 h. Serum decreased the efficiency of the resin to retain 3H-DA from culture medium, attenuated the difference in dopamine release between ECM and plastic cultures, and contributed to variations in 3H-TY uptake. The morphometric relationship between the cell membrane and the internal compartment in PC12 cells of different shapes was also characterized. The perimeter length and area of the midsection of cells were determined with a modular system for quantitative digital analysis. The perimeter length of cells on ECM was significantly greater than cells on plastic, whereas the internal areas were similar. The ratio of perimeter length to area (P/A) for all cells on ECM was 30% higher than the P/A ratio for cells on plastic. The ratio of P/A for a subpopulation of very flat cells on ECM was 70% higher than the ratio for round cells on plastic. Immunocytochemistry for tyrosine hydroxylase revealed a more diffuse distribution of this enzyme in cells on ECM. These data suggest that there is an increase in the ratio of cell surface area to cell volume as PC12 cells spread on ECM which could facilitate secretory vesicle fusion with the cell membrane, and hence, exocytosis. Although there is a concomitant increase in the secretion of dopamine and a decrease in the storage of dopamine, the change in cell shape does not appear to immediately alter the synthesis of dopamine.
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D002852:Chromatography, Ion Exchange; D004298:Dopamine / Q000096:biosynthesis*; D005109:Extracellular Matrix / Q000502:physiology*; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D010673:Pheochromocytoma / Q000378:metabolism* / Q000648:ultrastructure; D010969:Plastics; D051381:Rats; D014443:Tyrosine / Q000502:physiology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D010969:Plastics; D014443:Tyrosine; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine