Influence of ions and tonicity of RNA metabolism in Tetrahymena pyriformis

Net RNA degradation occurs in Tetrahymem pyrifmmis when this ciliate is suspended in a non‐nutrient medium. The quantity and quality of the excretion products is at least partially under the control of the ionic content and the tonicity of the cellular environment. The excretion of ultraviolet‐absorbing materials was found to be elevated by sodium ions in a medium isotonic to the culture fluid, or by a hypertonic environment. Magnesium counteracted these effects. In isotonic suspension, sodium and magnesium ions lowered orthophosphate excretion; however, sodium altered the nature of the phosphate products so that acidlabile phosphates were also excreted rather than solely orthophosphate. Similar results were obtained in a hypertonic environment with or without sodium. The degree of purine and pyrimidine loss from the cells in all conditions of suspension was reflected in the amount of RNA degraded. The ion and tonicity effects apparently reflect events which alter the stability of the RNA and the properties of the membrane system, resulting in changes in both the rate of RNA degradation and the nature of the excreted products. The rates of orthophosphate excretion appear to be affected by changes in the acid‐base balance within the cell which may be governed by the cation levels. The manipulation of the ionic content and tonicity of the medium offers a convenient method for obtaining cells reduced in RNA content.