Choline st erase and active transport of sodium 



chloride through the isolated gills of the crab 



Eriocheir sinensis (M.Edw.) 



by 



H. J. KOCH 



Labot -atone de ^joophysiologie de lUniversite, Louvain 



INTRODUCTION 



A number of freshwater insects and Crustacea share with Amphibia and fishes the 

 ability to transport mineral ions from very dilute solutions into a much more con- 

 centrated blood (see Krogh, 1939). 



From the point of view of general cellular physiology it certainly is a fortunate 

 circumstance that the structures responsible for this uptake in arthropods are com- 

 posed of only one single layer of cells. In the most favourable cases specialized cells 

 are assembled so as to form definite organs. The function of this type of organ has 

 been established on firm ground at least in the case of the anal papillae of Diptera 

 (Koch and Krogh, 1936; Koch, 1938; Wigglesworth, 1938; Krogh, 1939; Ramsay, 



1953)- 



Recently it has been possible to show that the gills of the freshwater crab Eriocheir 



sinensis (M.Edw.) will continue to absorb ions when isolated from the body. This 

 active transport occurs against a considerable concentration gradient (e.g., outside 

 medium 8 mM Na, blood up to 300 itim; Koch, Evans and Schicks, 1954a). 



By means of these gills it is now possible to study an ion-absorbing mechanism in 

 an arthropod without the interference of other parts of the body. These gills have 

 already proved to be promising material for the analysis of ion uptake, and their 

 considerable size makes them suitable for the further investigation of the biochemical 

 basis of active transport. Their homogeneous histological composition gives them in 

 this respect an advantage over the isolated frog's skin, which has contributed so much 

 to fundamental knowledge of active transport (Huf, 1935; Krogh, 1937; Ussing,. 

 1948; Ussing and Zerahn, 1951). 



The mechanism by which NaCl is actively taken up by the gills of the crab shows: 

 some remarkable features in common not only with the corresponding function in 

 the larvae of Diptera but even with ion-transport mechanisms in vertebrates. 



GENERAL CHARACTERISTICS OF THE ION ABSORPTION 



The ion-absorption mechanism present in the gill epithelium is able to work at high 

 speed: values of 02 mg. NaCl per gill per hour have been observed repeatedly with 



15 



