DIFFERENCES IN PROTEIN-PATTERNS OF GILL EPITHELIAL-CELLS OF THE FISH GILLICHTHYS-MIRABILIS AFTER OSMOTIC AND THERMAL-ACCLIMATION

Different protein patterns in gill epithelium of a euryhaline and eury thermal teleost fish (Gillichthys mirabilis, Family Gobiidae) in respo nse to long-term (2 months) osmotic and thermal acclimation were found for the first time. Gill epithelial cells were isolated to remove ext racellular proteins and quantify specialized cell types. Chloride cell s were identified on the basis of size (>10 mu m) and bright appearanc e after p-dimethylaminostyryl)-1-methyl-pyridinium-iodine] staining. S mall mitochondria-rich cells were < 5 mu m in diameter and showed inte rmediate fluorescence. Abundance of chloride cells and small mitochond ria-rich cells was significantly influenced by osmotic but not thermal acclimation (dilute seawater/25 degrees C: 1.4 +/- 0.2% chloride cell s, 11.9 +/- 4.6% small mitochondria-rich cells; seawater/25 degrees C: 2.4 +/- 0.6% chloride cells, 2.2 +/- 1.3% small mitochondria-rich cel ls; seawater/10 degrees C: 2.9 +/- 0.3% chloride cells, 1.2 +/- 0.7% s mall mitochondria-rich cells). Pavement cells, identified by low fluor escence and intermediate size (5-10 mu m), largely predominated under all conditions (> 85% of cells), Thus, they represented the major prot ein source in gill epithelium. Differences in protein patterns were de tectable using two-dimensional but not one-dimensional electrophoresis . Of 602 proteins identified by charge and molecular weight properties , only two were induced by high temperature (25 degrees C) and three i n response to cold acclimation (10 degrees C). Nine proteins were indu ced in diluted seawater-acclimated fish, whereas no seawater-induced p roteins were found. We hypothesize that proteins induced under dilute seawater conditions are important for the function of pavement cells i n gills of hyper-osmoregulating G. mirabilis.