Histological and enzymatic studies on the renal tubules of some marine elasmobranchs

✍ Scribed by Makoto Endo

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 705 KB
• Volume: 182
• Category: Article
• ISSN: 0362-2525
• DOI: 10.1002/jmor.1051820104

✦ Synopsis

Renal tubules in the dog shark, leopard shark, and red skate were examined histologically and analyzed histochemically for enzymes. Cells of the distal and collecting tubules exhibit extensive interdigitations and large intercellular spaces, suggesting that these tubules are sites of sodium reabsorption. Although Na-K-ATPase is very scarce to nonexistent in the distal and collecting tubules, very intense carbonic anhydrase activity in these segments indicates that they secrete large amounts of hyrogen ion and reabsorb sodium by H /Na exchange process. Epithelial cells of the necks are not interdigitated, tightly join adjacent cells, and have low enzyme activities. They seem to be passively permeable to the water. Necks are attached to the distal tubules with scant intervening stroma. It seems likely that the stroma has a high osmotic pressure resulting from absorption of solutes in the distal tubules. Water may be reabsorbed from necks to stroma because of a concentration gradient of the solutes distributed between these sites.