Effects of wheat germ agglutinin and colchicine on microtubules of the mitochondria-rich cells and Ca2+ uptake in tilapia (Oreochromis mossambicus) larvae.

The organization of the microtubules and actin filaments in the gills of tilapia (Oreochromis mossambicus) larvae was revealed by confocal microscopy. The fluorescence intensity of the microtubules in the gills was increased by adding wheat germ agglutinin (WGA, 40 ng ml-1) to the ambient water for 30 min, but the staining pattern of the actin filaments was not changed. The fluorescence intensity of the microtubules in the gills was decreased by treatment with the microtubule-disrupting reagent colchicine at 0.2 mmol l-1 for 4 h. WGA treatment concurrently raised Ca2+ influx rates, and the increase was particularly large when the larvae were kept in water with extremely low Ca2+ levels ([Ca2+]=0.002 mmol l-1). Colchicine treatment, in contrast, reduced the Ca2+ influx rate. These results indicate that the microtubule network in tilapia gills, particularly in mitochondria-rich cells, could play a critical role in the uptake of Ca2+ in tilapia larvae.