Immunocytochemical localization of cyclic AMP in Tetrahymena

Cytochemical investigation into the Ca-dependence of positive and negative hormonal imprinting in Tetrahymena

Insulin gives rise to positive imprinting in Tetrahymena pyriformis, but to negative imprinting in T. thermophila, as revealed by the respective increases and decreases in the insulin-binding capacity of these organisms observed during later interactions with this hormone. We found that changes in insulin-binding capacity exhibited parallelism with fluctuations of the levels of free, intracellular Ca2+ detectable by Quin-2 labeling. An exception was the second interaction of T. thermophila with insulin, which although showing a positive trend, produced a relatively small increase in the level of intracellular Ca2+. These observations suggest an interrelationship between hormone-binding capacity and the fluctuation of intracellular Ca2+ levels. Either hormone binding depends on the availability of Ca2+, or, alternatively, the latter depends on the binding capacity. Further studies are required to elucidate the true nature of this interdependence.

Electron microscopic localization and hormonal (diiodotyrosine) induction of adenylate cyclase in the Tetrahymena

Normal Tetrahymena cells exhibited adenylate cyclase activity exclusively in association with pinocytotic vesicles, whereas those treated with diiodotyrosine (T2) for growth stimulation showed it in association with the cell membrane, and intracellularly inside many dense bodies. It appears that hormonally activable adenylate cyclase is an inherent component of the Tetrahymena.