Trophic stimulation of conversion of cultured newt iris cells into lens cells by a bovine thyrotropin preparation

Abstract

The bovine thyrotropin preparation NIH-TSH-B8 can stimulate lens formation from cultured dorsal irises of the newt Notophthalmus viridescens. We studied the effect of thyrotropin NIH-TSH-B8 on dissociated iris cells in culture. Cell suspensions prepared from dorsal irises were maintained for up to 110 days in diluted Leibovitz L-15 medium supplemented with 10% fetal calf serum. Under these conditions, thyrotropin NIH-TSH-B8 increased the numbers of spherical and mitotic cells, clusters of γ-crystallin containing depigmented cells (lentoid bodies), and clusters of pigmented cells. The log phase of this process was remarkably shortened. However, the lag phase in treated cultures was similar to to that of untreated cultures. When the treatment was started after 4 days of culture, iris cell cultures responded similarly to continuously treated cultures. However, a delay of 15 days gave variable results. When thyrotropin NIH-TSH-B8 was removed on day 4 or 15 of cultivation, the response of the cell population resembled that of controls. These results suggest that this hormone preparation increases the number of pigmented iris cells that shift into the pathway of cell type conversion.