Effect of oxytocin and its analogues on the phagocytosis of Tetrahymena:: Outstanding impact of isotocin

The influence on the phagocytosis of Tetrahymena pyriformis of oxytocin and its analogues (derivatives) tocinoic acid, isotocin and the tyrosin supplemented tail part (Tyr-Pro-Leu-Gly=Tyr) as well, as the impact of oxytocin and its analogues on the phagocytosis of the populations of Tetrahymena selected to itself and to the three latter molecules were studied in the experiments. The molecules tested did not influence phagocytosis in the random populations. However, populations selected to isotocin have a higher phagocytotic activity (without further stimuli) and also reacted to oxytocin or isotocin with an increased phagocytosis. Also isotocin was the only molecule the lselection of which resulted in a "size-altered" population (smaller cells), and produced minimal number of non-phagocytizing "0" cells. Populations selected to tocinoic acid or Tyr reacted with a decrease of phagocytosis to oxytocin treatment. The experiments calls attention to the possible evolutionary role of (chemotactic) selection to signal molecules, to the differentiating ability of Tetrahymena between signal molecules and to the advantage of phylogenetically older molecules from this point of view.