[Studies on the phospho-tyrosine proteins during the proliferation cycle of cultured aortic smooth muscle cells].

The dynamic change and distribution of phospho-tyrosine proteins (P-tyr-Pr) during the cell cycle of cultured rabbit aortic smooth muscle cells (ASMC) were studied by ELISA and immunohistochemical technique. The antibody which was specific for P-tyr-Pr was prepared by immunizing California white rabbits with synthesized phospho-tyrosine bovine serum albumin, and then the IgG obtained was purified and coupled to horseradish peroxidase to make it ready for use in ELISA. We find that the content of particle P-tyr-Pr fluctuated in G1 stage, both in the cytosol and in the nucleus, being the highest at late G1 stage (9 h after G0), and the content of particle P-tyr-Pr was much higher in the nucleus than in the cytosol throughout G1 stage. The immunohistochemical study, which locates the distribution of P-tyr-Pr in ASMC, also revealed that the nuclei were stained much darker than the cytosol, and the total P-tyr-Pr content (including both particle and soluble P-tyr-Pr) was the highest at late G1 stage, or higher than at G0 and before S stage (12 h after G0). But the distribution before S stage was similar to that at late G1 stage, and although the total content before S stage was lower than at late G1 stage, it was evidently higher than that at G0 stage. This last finding might have some bearing on the role of tyrosine protein kinase in the events of a cell cycle.