Absorption of fluid from isolated intestine of the toadfish, Opsanus tau

Abstract

1. 1. Movement of water from isolated intestinal sacs of toadfish, Opsanus tau, was measured by using C 14-inulin as a tracer. Changes in Na concentration were followed also. 2. 2. Net water absorption was 25·7 ± 14·5 (S.E.) μl hr −1g −1, wet weight, when identical Ringer solutions bathed mucosal and serosal surfaces. Absorption decreased in the presence of 10 −3 M NaCN and 10 −3 M NaCN plus 10 −4 M IAA. † † IAA = iodoacetic acid. 3. 3. The direction of water movement was reversed and mucosal concentration of Na rose when five-sixths of the mucosal NaCl was replaced by the non-penetrating solute, mannitol. When only one-third of the mucosal NaCl was replaced with mannitol, water absorption continued and mucosal Na fell, but net water flow was reversed in the presence of 10 −3 or 10 −4 M IAA plus 10 −4 M DNP. ‡ 4. 4. A possible interpretation is that salt and water movements are coupled and that salt transfer can occur against a concentration gradient.