Tetrahymena cells distinguish insulin preparations according to either their amorphous and crystalline form or their bovine and porcine origin: aspects of hormone binding and chemotaxis in relation to imprinting.

Bovine insulin had a strong negative effect on the chemotaxis of Tetrahymena at the first encounter with the hormone. The crystalline porcine insulin proved to be neutral, while the amorphous porcine insulin had a significant positive chemotactic effect. At the second encounter with the hormone the presence of imprinting was detectable with bovine insulin and induced a significant positive chemotaxis. The chemotactic effect of amorphous porcine insulin was depressed while crystalline porcine insulin expressed the most significant positive chemotactic effect. In the binding of hormones there was unambiguous positive imprinting independently from the species specificity and from the physicochemical condition of the insulins. Tetrahymena discriminated at both the first and second encounters between the bovine and porcine insulins which differed in two amino acids. The imprinter capacity evident in binding was independent of the chemotactic preference and the imprinting embodied in chemotaxis.