The Calcium-sensitive Cells of the Pars Intermedia in the Eel

Abstract

Olivereau, M., Olivereau, J . 1982. The calcium-sensitive cells of the pars intermedia in the eel. Kinetics of their response to environmental changes. (In the pituitary, the PAS-positive calcium-sensitive (Ca-s) cells of the pars intermedia appear less active in seawater (SW)-than in freshwater (FW)-adapted eels. The kinetics of their response during adaptation to SW or readaptation to FW was investigated. Morphometric studies show that transfer to SW induces a rapid nuclear atrophy which accentuates in eels kept for several weeks in SW. Readaptation to FW stimulated the Ca-s cells after 2--10 days; after 1 or 2 months, the cells tend to be similar to those of eels kept in FW. Plasma calcium decreases slightly but significantly in SW eels. The response of the Ca-s cells is not modified by an ovine prolactin treatment inducing hypercalcemia, hypernatremia and stimulation of the corpuscles of Stannius. Minor changes occurring in the MSH cells remain difficult to interpret; the short stimulation during readaptation to FW may be related to a stress effect and/or to release of other peptides present in the MSH cells of fish.