![]() ![]() Co-identity of inulin space with ECF volume was assumed. Consequent cell swelling due to tissue hypoxia may also be important ( Macknight & Leaf, 1977).Įxtracellular fluid (ECF) volumes of acclimating and acclimated animals were measured using - and hydroxymethyl inulin (Radiochemical Centre, Amersham). It is not known if this leads directly to general cellular swelling and rupture causing cell death on a large scale or whether, as a result of tissue swelling, circulatory restriction occurs as a first stage, resulting in reduced blood flow to important organs and possible ischaemia. In acute osmotic stress, it is assumed that the cellular regulatory mechanisms are unable to cope with either the rate or amplitude of the extracellular osmotic pressure changes. In these soft-bodied species, water enters both extra- and intracellular compartments. Recently, it has been found that some species, with limited capacities to regulate extracellular concentration, tolerate large changes in the volumes of their body fluid compartments (Arenicola: Freeman & Shuttleworth, 1977 Glycera: Machin, 1975). The effectiveness of this cellular volume control can be investigated by measuring changes in body fluid compartment volumes during acclimation to different salinities. These processes must occur at rates appropriate to produce intracellular osmotic pressure changes matching those taking place extracellularly, if there is to be no cellular shrinkage or swelling by osmotic transfer of water. In hyperosmotic media, the ECF volumes increased significantly (to a maximum of 143 %) but, in contrast to the response in hyposmotic conditions, showed only a partial return to the original volumes. Calculation of intracellular water contents suggests that a volume limitation phase precedes the regulatory return to the original volume. After transfer of the crabs to media hyposmotic to the haemolymph, ECF volumes decreased transiently to 74♸% of the initial volume, but within 40 h in 26% sea water original volumes were restored. Earlier reports of a relatively slow marker distribution, indicated from clearance curves, can be explained by high clearance rates occurring when frequent blood sampling was carried out. Initial investigations showed that there was a rapid equilibration into this compartment of the ECF markers used (inulin and hydroxymethyl inulin). Changes in extracellular fluid (ECF) volume of Carcinus maenas (L.) were studied in vivo during acclimation to low and high environmental salinities. ![]()
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