Suramin and heparin: aspecific inhibitors of mesoderm induction in the Xenopus laevis embryo.
Xenopus embryos in solutions containing suramin show a dose-dependent decrease in the formation of dorsoanterior structures. Continuous treatment with 1 mM suramin produces embryos without mesodermal derivatives but with mesenchymal cells. Brief immersions of 20 min were used to determine the most sensitive stages and to establish dose-effect curves: a 20 min treatment with 3 mM suramin at stages 7-8.5 produces blastula-like embryos, never classified before, with atypical epidermis, cells full of yolk and mesenchyme in between. The lack of dorsal mesoderm was confirmed by an RNase protection assay with alpha-cardiac actin probe. Heparin also causes a reduction in dorsal structures, but its action is weaker and and there are also strong toxic effects such as superficial cell dissociation. The effect of heparin is dose-dependent and brief immersions show a very sensitive period around stage 6.5. The lowest DAI obtained is 1.5, an extremely microcephalic embryo with forked tail codes, a stocky notochord, and abnormally shaped, abundant neural tissue. Immunofluorescence shows that the distribution of fibronectin-containing fibrils is normal in heparin-treated embryos, whereas there are no such fibrils in suramin-treated embryos at control stage 12.
Cardellini
P
P
Dipartimento di Biologia, Università degli Studi di Padova, Italy.
Polo
C
C
Coral
S
S
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004625:Embryo, Nonmammalian / Q000648:ultrastructure; D004627:Embryonic Induction / Q000187:drug effects*; D005353:Fibronectins / Q000032:analysis; D005455:Fluorescent Antibody Technique; D006493:Heparin / Q000494:pharmacology*; D008648:Mesoderm / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*; D008855:Microscopy, Electron, Scanning; D013498:Suramin / Q000494:pharmacology*; D014982:Xenopus laevis / Q000196:embryology*
D005353:Fibronectins; D013498:Suramin; D006493:Heparin