Chloroquine and monensin inhibit induction of DNA synthesis in rat arterial smooth muscle cells stimulated with platelet-derived growth factor.
The weak base chloroquine and the Na+/H+ ionophore monensin were used to study the role of lysosomes in the induction of DNA synthesis by platelet-derived growth factor (PDGF) in rat arterial smooth muscle cells cultivated in vitro. The results show that PDGF initiates DNA synthesis in a defined, serum-free medium. This indicates that a single factor may control, directly or indirectly, the transition from the G0 to the G1 phase, the progress through the G1 phase, and the entrance into the S phase of the cell cycle. It is further demonstrated that PDGF has to be present throughout most of the prereplicative period (12-16 h) to induce DNA synthesis in the maximum number of cells, suggesting that one or more processes need to be stimulated continually or successively to push the cell into the S phase. Chloroquine and monensin inhibit induction of DNA replication by PDGF, with maximum effect at 50 microM and 5 microM, respectively. To be fully active, the drugs have to be added within 4-8 h after the growth factor, but a partial inhibition persists if they are added at any time during the prereplicative period. Both drugs reduce PDGF-stimulated RNA and protein synthesis, and suppress degradation of [3H]leucine-labeled cellular protein and [125I]-labeled PDGF. Fine-structurally, they give rise to an accumulation of lysosomes or prelysosomal vacuoles with inclusions of incompletely degraded material. These findings suggest that the mitogenic effect of PDGF is dependent on a normal function of lysosomes during the prereplicative phase, especially its first half (0-8 h).
Bottger
B A
BA
Department of Medical Cell Biology, Karolinska Institutet, Stockholm, Sweden.
Sjölund
M
M
Thyberg
J
J
D000818:Animals; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis* / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007930:Leucine / Q000378:metabolism; D008297:Male; D008985:Monensin / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000098:blood supply / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014316:Tritium; D014529:Uridine / Q000378:metabolism
D010982:Platelet-Derived Growth Factor; D014316:Tritium; D002738:Chloroquine; D004247:DNA; D008985:Monensin; D007930:Leucine; D014529:Uridine