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Protamine sulfate inhibition of serum-induced mitogenic responses: differential effects on normal and neoplastic
Abstract:
Protamine sulfate reversibly inhibits serum-induced mitogenic stimulation of several nontransformed and neoplastic cell types in vitro. Fifty percent inhibition was induced by approximately 120-150 micrograms protamine sulfate/ml. Cells were affected directly, and inhibition depended on the duration of cell exposure. Heparin, chondroitin sulfate, heparan sulfate, and dextran sulfate neutralized protamine sulfate effects during the early stages of treatment. Nontransformed cells [bovine aortic endothelial cells, adult human gingival fibroblasts (strains 423 and 1101), fetal rat skin (strain 921-K) and muscle fibroblasts] required longer exposure to induce inhibition than did neoplastic cells [rat 3-methylcholanthrene-induced fibrosarcoma cell lines (MCA-6 and MCA-9), a macrophage-like cell line (NCTC-3749), Walker 256 rat carcinoma cells (ATCC-CCL-38), rat Morris hepatoma cells (ATCC-CCL-144), murine melanoma cells (B16), and rat bladder squamous cell carcinoma cells (804-G)]. Other polycationic compounds, including histone type VIII-S, poly-L-lysine, poly-L-arginine, and protamine (free base), were also effective inhibitors, whereas the basic proteins cytochrome c and lysozyme had no effect. Poly-L-histidine, poly-L-glutamic acid, poly-L-aspartic acid, and dextran blue also had no inhibitory effect.
Insights
Protamine sulfate effectively inhibits cell growth by blocking serum-induced mitogenic stimulation. This inhibition is reversible and varies between normal and cancer cells, with heparin and other sulfates counteracting its effects.
Area of Science:
- Cell Biology
- Biochemistry
Background:
- Mitogenic stimulation drives cell proliferation.
- Protamine sulfate is a polycationic molecule with potential biological activities.
Purpose of the Study:
- To investigate the inhibitory effects of protamine sulfate on cell proliferation.
- To compare the sensitivity of different cell types to protamine sulfate.
- To identify factors that modulate protamine sulfate's inhibitory action.
Main Methods:
- In vitro cell culture experiments.
- Exposure of various nontransformed and neoplastic cell lines to protamine sulfate.
- Assessment of cell proliferation inhibition.
- Testing the neutralizing effects of various sulfated compounds and other polycations.
Main Results:
- Protamine sulfate reversibly inhibits serum-induced mitogenic stimulation in multiple cell types.
- Neoplastic cells generally required shorter exposure times for inhibition compared to nontransformed cells.
- Heparin, chondroitin sulfate, heparan sulfate, and dextran sulfate neutralized protamine sulfate's effects.
- Other polycations like poly-L-lysine and poly-L-arginine also showed inhibitory effects.
Conclusions:
- Protamine sulfate is a potent inhibitor of cell proliferation.
- Differential sensitivity exists between normal and cancer cells.
- The inhibitory action of protamine sulfate can be modulated by specific sulfated polysaccharides and other polycations.