Cell volume regulation in the perfused liver of a freshwater air-breathing catfish Clarias batrachus under aniso-osmotic conditions: Roles of inorganic ions and taurine

Journal of biosciences

Carina Goswami¹  Nirmalendu Saha1¹ 

[1] Biochemical Adaptation Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793 022, India$$

关键词: Hypertonicity;    hypotonicity;    liver mass;    regulatory volume decrease;    regulatory volume increase;    taurine;   

DOI  :  

来源: Indian Academy of Sciences

【 摘 要 】

The roles of various inorganic ions and taurine, an organic osmolyte, in cell volume regulation were investigated in the perfused liver of a freshwater air-breathing catfish Clarias batrachus under aniso-osmotic conditions. There was a transient increase and decrease of liver cell volume following hypotonic (–80 mOsmol/l) and hypertonic (+80 mOsmol/l) exposures, respectively, which gradually decreased/increased near to the control level due to release/uptake of water within a period of 25–30 min. Liver volume decrease was accompanied by enhanced efflux of K+ (9.45 ± 0.54 𝜇mol/g liver) due to activation of Ba2+- and quinidine-sensitive K+ channel, and to a lesser extent due to enhanced efflux of Cl¯ (4.35 ± 0.25 𝜇mol/g liver) and Na+ (3.68 ± 0.37 𝜇mol/g liver). Conversely, upon hypertonic exposure, there was amiloride- and ouabain-sensitive uptake of K+ (9.78 ± 0.65 𝜇mol/g liver), and also Cl¯ (3.72 ± 0.25 𝜇mol/g liver). The alkalization/acidification of the liver effluents under hypo-/hypertonicity was mainly due to movement of various ions during volume regulatory processes. Taurine, an important organic osmolyte, appears also to play a very important role in hepatocyte cell volume regulation in the walking catfish as evidenced by the fact that hypo- and hyper-osmolarity caused transient efflux (5.68 ± 0.38 𝜇mol/g liver) and uptake (6.38 ± 0.45 𝜇mol/g liver) of taurine, respectively. The taurine efflux was sensitive to 4,4′-di-isothiocyanatostilbene-2,2′-disulphonic acid (DIDS, an anion channel blocker), but the uptake was insensitive to DIDS, thus indicating that the release and uptake of taurine during volume regulatory processes are unidirectional. Although the liver of walking catfish possesses the RVD and RVI mechanisms, it is to be noted that liver cells remain partly swollen and shrunken during anisotonic exposures, thereby possibly causing various volume-sensitive metabolic changes in the liver as reported earlier.

【 授权许可】

Unknown