[Response of the pars intermedia of the goldfish pituitary to deionized water, buffered or not, and to calcium and magnesium supplementation (author's transl)].

In the goldfish, one cell type of the pars intermedia, slightly PAS positive, is highly stimulated in deionized water (E Dés). This response is not influenced by the pH of the water (E Dés pH 5.3, E Dés buffered with imidazole pH 6.7) for 20 days. Stimulation is prevented when the E Dés is supplemented with CaCl2 (2mM), but it is not affected by the addition of MgCl2 (2 mM). When goldfish are kept in E Dés for 20 days, and subsequently in E Dés supplemented with calcium gluconate (1 mM), a granule storage occurs in the cytoplasm of the enlarged cells within 48 hours. These cells are therefore sensitive to the lack or presence of calcium in the environment. The term of calcium-sensitive (Ca-s) cells appears justified in the goldfish, as in the eel; their putative role in the control of the pigmentation is not evident.