HORMONAL-CONTROL OF THE IN-VITRO UPTAKE OF [S-35] SULFATE BY CARTILAGE OF XENOPUS-LAEVIS TADPOLES

The influence of various mammalian hormones and growth factors on the skeletal growth in the clawed toad was examined in vitro by monitoring the uptake of [S-35]sulfate by tadpole's hindlimbs. Autoradiographic studies demonstrated that the isotope was mainly incorporated into the cartilage. Sulfate uptake was significantly stimulated by 13 nM insul in-like growth factor I (IGF-I) in all experiments. The effect of 13 n M IGF-II was statistically significant only in approximately 50% of th e experiments. Insulin was inconsistently effective. A significant sti mulation was found using 1300 nM insulin. Neither prolactin and growth hormone nor the thyroid hormones thyroxine and triiodothyronine affec ted the [S-35]sulfate uptake in vitro. The results indicate that carti lage growth in amphibians is mainly stimulated by IGF-I and to a less extend by IGF-II like in mammals. (C) 1997 Elsevier Science Inc.