Response of PAS-positive cells of the pituitary pars intermedia in the teleost Carassius auratus to acid water

Abstract

Summary. The PAS-positive or PIPAS cells in the pars in termedia of goldfish are activated after reduction of the pH of the ambient freshwater from 7.5 to 3.5. The cells increase in number and exhibit a five-fold increase in cell volume. Granular endoplasmic reticulum occupies most of the cytoplasm. Goldfish PIPAS cells (also termed calciumsensitive cells) are thought to have a hypercalcemic func tion. Therefore, their activation in acid water may be caused by the severe drop in plasma calcium concentration follow ing exposure of the fish to low water pH. However, activa tion of the PIPAS cells in response to acidification of the water is not prevented when the calcium concentration of the water is increased to levels that result in hypercalcemia instead of hypocalcemia. Activation of the PIPAS cells oc curs also in fish exposed to acidified freshwater enriched with NaCl to an osmolarity similar to that of the blood. This prevents the reduction in plasma osmolarity and Na ' and Cl" concentrations that follow exposure of goldfish to acidified normal freshwater. Our observations do not support the hypothesis that the PIPAS cells in goldfish pro duce a hypercalcemic hormone, or indeed any hormone involved in calcium metabolism or osmoregulation. The cells may be implicated in ¡icid-base regulation (a character istic of many types offish when exposed to acidified water) but the evidence is indirect.

Isolation and characterization of somatolactin, a new protein related to growth hormone and prolactin from Atlantic cod (Gadus morhua) pituitary glands

“…These results show some correlation with older observations indicating the pars intermedia PAS-positive cells, previously shown to be the site of SL production (Rand-Weaver et al, 1991), to become activated during sexual maturation [quoted in Ball and Baker (1969)]. More recent histological studies have shown the PAS-positive cells to become activated in fish exposed to hypocalcaemic conditions (Olivercau ct al., 1981(Olivercau ct al., , 1985Ball et al, 1982), acidification of water (Wendelaar-Bonga et al, 1986), and dark backgrounds (van Eys, 1980; Ball & Batten, 1981). However, our studies suggest that the data concerning the PAS-positive cells and sexual maturation should be reexamined and a possible role for SL during reproduction investigated in addition to ionor coloration-controlling functions.…”

“…0006-2960/91 /0430-1509S02.50/0 PAS-positive cells have been considered to produce a factor involved in such diverse functions as calcium regulation (Ball et al, 1982;Olivereau et al, 1985), acid-base metabolism (Wendelaar-Bonga et al, 1986), adaptation to background (Ball & Batten, 1981), and reproduction [quoted in Ball and Baker (1969)].…”