Ion and Water Transport in Isolated Intestine of the Marine Teleost, Cottus Scorpius

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Abstract
The unidirectional sodium fluxes from mucosa to serosa and from serosa to mucosa have been studied in the isolated small intestine of Cottus scorpius, bathed in Ringer and sulphate Ringer, by use of the isotope 22Na. In addition the unidirectional chloride fluxes have been studied in Ringer and choline Ringer using the isotope 36Cl. In Ringer the mean ± S.E. values of these fluxes have been found to be: for sodium, 8·4+ 0·6 (serosa to mucosa) and 23·9+0·7 (mucosa to serosa) /μequiv. cm. -2 hr. -1 and for chloride, 10-5 ± 0-9 (serosa to mucosa) and 21·9 ± 0·9 (mucosa to serosa) μequiv. cm. -2 hr. -1. In sulphate Ringer the mean ± s.E. values for sodium were 4‘5 ± 0·3 (serosa to mucosa) and 6·8 ± 0·6 (mucosa to serosa) /μequiv. cm. -2 hr. -1 and in choline Ringer the mean ±S.E. values for chloride were 5·1 ± 1·0 (serosa to mucosa) and 5·94 + 0·9 (mucosa to serosa) /μequiv. cm. -2 hr. -1. The respiration rates of pieces of intestine placed in Ringer, sulphate Ringer, choline Ringer and artificial sea water have been measured in a Warburg apparatus. The mean ±S.E. values of oxygen consumption in these media have been found to be 0·4 ± 0·2 (Ringer), 0·3 ± 0·2 (sulphate Ringer), 0·3 ± 0·2 (choline Ringer) and 0·1 ±0·2 (artificial sea water) μ1. O 2/mg. dry weight.hr. The electric potential differences between identical serosal and mucosal media bathing isolated intestines have been measured. The mean + s.E. values of the potential difference in Ringer, sulphate Ringer, choline Ringer and artificial sea water have been found to be +0·6 ± 0·3, +2·2 ± 0·2, + 0·8 ±0·3 and +1·3+ 0·2 mV., respectively (mucosal medium taken as reference). The hydraulic conductivity of the isolated intestine has been found by measuring the change in net water flux arising from the creation of an osmotic gradient across this tissue. Net water flux was measured by the change in weight of normal filled sacs. The mean + s.E. value for this parameter has been found to be 0·22 ± 0·05 μ1/cm. 2 mosmolar. hr. (or 2·4+0·6 cm. sec. -1 atm. -1). It has been found that, when artificial sea water is placed in the lumen of the intestine bathed in Ringer, a net flow of water into the lumen occurs. This net water flux falls to zero at a time dependent on the luminal volume (to be diluted) and, thereafter, a net water flux (mucosa to serosa) is established. The net water movement across isolated intestines bathed on both sides by identical media has been studied. The mean ± s.E. values for net water flux (mucosa to serosa) have been found to be: in Ringer, 8·1±0·8, in sulphate Ringer, 3·6±0·5 and in choline Ringer, 6·7 ± 0·6 µ. cm. -2 hr. -1. The results are interpreted as showing that the net transfer of sodium and chloride ions between identical Ringer solutions is achieved by some process whereby these ions are ‘pumped’ in the form of electrically neutral sodium chloride. It is considered that there is some evidence for the existence of a frictional interaction between sodium chloride and water as they pass across the intestine.