Production of Intercellular Hormones

Abstract

IN the investigation of metabolic controlling factors (intercellular hormones) appearing in the suspending fluid when cell aggregates are subjected to lethal ultra-violet¹, X-rays², and other external agents, it seems to us of particular interest to determine whether such substances are released by living cells into the intercellular fluids or are simply dead-cell disintegration products. To study this question, suspensions of yeast in isotonic salt solution were irradiated with lethal ultra-violet for periods from 9 to 24 hours under such conditions that the full irradiation period was required to kill 90 per cent of the cells. Samples taken out at regular intervals were filtered through Berkefeld filters, and the growth potencies of the filtrates compared with those of filtrates from control suspensions allowed to stand for equal periods without irradiation. The extent of killing was determined by methylene blue staining and by plating. Maximum production of growth factors (intercellular wound hormones) preceded maximum rate of killing and occurred while most of the cells were still living.