Enzymes, non-enzymatic proteins and other organic molecules are vital components in living cells.
Their respective function depends on specific spatial configurations which are linked to intracellular conditions.
Any fluctuation of these conditions, beyond certain threshold values, such as a disruption of ionic regulatory
mechanisms, can lead to the destabilisation of a finely balanced intracellular dynamic physiological equilibrium
or homeostasis. Hydromineral homeostasis in aquatic organisms is maintained by a complex endocrine controlled
array of specialised cross-membrane ion transport systems and the regulation of membrane water permeability.
Depending on how aquatic organisms maintain hydromineral homeostasis, they can be roughly divided into two
groups: osmoconformers and osmoregulators; the former are mostly invertebrates with high water permeability,
the latter include some invertebrates and most fish species, whose permeable external epithelia are usually
restricted to the gills. Other important organs involved in hydromineral regulation include the intestine and the
various phyla-specific organisational types of renal systems. Environmental concentrations of organotin
compounds, such as tributyltin and triphenyltin, have been shown to interfere with the maintenance of
hydromineral homeostasis by inhibiting ATPases and affecting membrane permeability for water. The present
chapter reviews the impact of organotin exposure on fresh- and seawater organisms of various phyla by
examining the histophathological, physiological and molecular interactions of organotin compounds with relevant
enzymes, membranes, the endocrine system, and the consequential ramifications for individuals, populations and
community structure in aquatic ecosystems.
Keywords: Hydromineral regulation - gills - membranes- osmosis - ionic flux - organotins - ATPase.
