Comparison of newt lens regeneration stimulating activity in preparations of mammalian thyrotropin and fibroblast growth factor purified by various methods.

Irises of the newt Notophthalmus viridescens will regenerate a new lens in organ culture in the presence of the bovine thyrotropin preparation NIH-TSH-B8. It is not certain, however, whether thyrotropin itself is responsible for this stimulatory effect. To elucidate this problem further we compared the lens regeneration stimulating activity of thyrotropin preparations from several species, prepared by various methods. The lowest effective concentrations were approximately 3.0 micrograms ml-1 for the bovine NIH-TSH-B8 and 1.4 micrograms ml-1 for the ovine NIAMDD-oTSH-9 preparations. At those lowest concentrations, lenses with elongating lens fiber cells (stage 6) and enlarged lens fiber core (stage 8) were obtained, respectively, and the lens-fiber-specific protein gamma-crystallin was present in both cases. The crude bovine thyrotropin fraction, Sigma-TS-10, stimulated lens regeneration only at the highest concentration, 1400 micrograms ml-1. Bovine Pierce-bTSH, the purest thyrotropin preparation, stimulated lens regeneration sporadically at the lower concentration of 0.04 micrograms ml-1 up to the advanced stage 9 with large lens fiber core and flattened lens epithelium in one of nineteen irises. The pituitary fibroblast growth factor is a known contaminant of thyrotropin preparations. The preparation CR-FGF-40002 at concentrations between 0.001 and 0.1 microgram ml-1 did not promote lens regeneration. Therefore, the lens regeneration stimulating activity in thyrotropin preparations is not attributable to the fibroblast growth factor, and may also be independent of thyrotropin because the lens regeneration stimulating activity is not proportional to the thyrotropic activity in the preparations examined.