Regulatory volume increase in nematocytes isolated from acontia of Aiptasia diaphana (Cnidaria, Anthozoa).

Nematocytes, Cnidarians stinging cells used primarily in capturing prey or in turning away predators, can regulate their volume under 35% hyposmotic shock showing regulatory volume decrease (RVD). In this study, for the first time, we investigate the capability of nematocytes to regulate their volume under hypertonic conditions, through regulatory volume increase (RVI). The experiments were carried out in acontial nematocytes of Aiptasia diaphana (Cnidaria: Anthozoa) isolated by the chemical method of applying 605 mM SCN-. Channel inhibitors, as amiloride, Gd3+, NPPB, DIDS, bumetanide and ion substitution have been employed to assess the role of ions in such volume regulation mechanisms. Our results suggest that nematocytes are able to perform RVI. The regulatory volume recovery process after hypertonic stimulation involves Na+ conductance and Na+/K+/2Cl- cotransport but not Cl- conductive pathways. Further studies will be necessary to better define such mechanisms and RVI control signalling, taking into account that the nematocyte is known to be a very primitive eukaryotic cell.