Specific induction of 68 KD protein synthesis in rabbit smooth muscle cells by growth stimuli in platelets: comparison of intimal and medial SMC.
We examined the influence of growth stimuli in heat-treated platelet extract on specific protein synthesis in the early phase of the cell cycle prior to the initiation of DNA synthesis in cultured rabbit aortic smooth muscle cells (SMC). The extract preferentially stimulated the synthesis of a cytoplasmic protein with a molecular weight of 68000 (p68) and an isoelectric point of around 6.3. Stimulation of p68 synthesis occurred within 1 h after the addition of heat-treated platelet extract to growth-arrested and quiescent SMC, continued until 4 h after stimulation, and then returned to the baseline level. Actinomycin D preferentially inhibited p68 synthesis. In SMC prepared from atheromatous plaques from the aorta of hyperlipidemic rabbits (I-SMC), the amount of DNA synthesis and of p68 synthesis by heat-treated platelet extract were less than those of SMC prepared from normal media (M-SMC), suggesting that the decreased capacity for cell proliferation of I-SMC in response to heat-treated platelet extract was due to the down-regulation of signal transduction in the early G0/G1 phase of the cell cycle.
Nishida
K
K
Research Institute, Daiichi Seiyaku Co., Ltd., Tokyo, Japan.
Tomikawa
M
M
D000818:Animals; D001013:Aorta, Thoracic; D001161:Arteriosclerosis / Q000378:metabolism*; D001792:Blood Platelets / Q000502:physiology*; D002457:Cell Extracts / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D006358:Hot Temperature; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D014176:Protein Biosynthesis; D012313:RNA / Q000096:biosynthesis; D011817:Rabbits
D002457:Cell Extracts; D003609:Dactinomycin; D012313:RNA