Lung development under the influence of thiourea and L-thyroxine. Retarding and toxic effects of thiourea.

Chick embryos were treated on day 17 of incubation with 32.8 mumol thiourea or 18.9 nmol L-thyroxine. As was already known from previous studies, hatching was delayed and accelerated, respectively, under these conditions. The premature induction of hatching by L-thyroxine was accompanied by an advanced development of the pulmonary structure and of the circulation and by a premature absorption of the parabronchial liquid. Thiourea exerted an opposite effect on these parameters. In several cases the structural formation of the parabronchii was suppressed after treatment with thiourea. Furthermore, parabronchial liquid accumulated in those embryos, the hatching of which was suppressed. It is suggested that these changes represent a toxic effect of thiourea rather than a retardation of pulmonary development.