Kinetic analysis and partitioning of sodium and chloride influxes across the gills of sea water adapted trout.

Abstract

SUMMARY1. Sodium and chloride influxes across the gills of sea water adapted trout were studied with the perfused isolated head technique.2. The haemodynamic scheme describing anastomoses between efferent gill arteries and the filamentous sinus was confirmed and utilized to determine partitioning of sodium and chloride influxes.3. Two routes of sodium and chloride entry were demonstrated, one lamellar and the other sinusal. The lamellar sodium and chloride fluxes are respectively 133 ± 21*8 and 271 + 43-7 ptequiv/hr. 100 g. The sinus sodium and chloride fluxes are: 50 + 18X3 and 50 + 11-3 ,uequiv/hr. 100 g.4. The relative permeabilities of the apical and basal barriers of the lamellar epithelium were determined with influx experiments coupled to radioactive unloading experiments. The basal membrane is 30 times less permeable than the apical to sodium, while this ratio is 45 for chloride. Thus, the basal membrane represents the limiting factor in salt movement across the bronchial epithelium.5. The intracellular pools of the lamellar compartment were calculated for sodium: 1 1+0 17,uequiv/t00g of fish weight; and for chloride:541 + 0-83 gequiv/100 g of fish weight.

Kinetic study of gill epithelium permeability to water diffusion in the fresh water trout,Salmo gairdneri: Effect of adrenaline

“…In ordinate logarithm of the quantity of radioactivity appearing per unit of time in the external (e) and in the internal (A) lamellar compartment. Insert represents the graphical determination of the fast exponentials (Girard & Payan, 1977a) Figure 3 shows the curves of radioactive discharge from the intermediate compartment into the external medium and into the perfusion liquid in the absence of adrenaline. Analysis of these curves demonstrates that for water two exponentials are obtained having different slopes for the external and internal compartments.…”

“…The unidirectional diffusion fluxes across these two barriers at equilibrium (J21 and Jga), as well as overall unidirectional transepithelial flux (J), were also measured and are expressed as ml-min-l.100g -~ (see Girard & Payan, 1977a). The size of the pool (ml-100g -1) participating in transepithelial water flux is given by the equation (Girard & Payan, 1977a) transflux pool -K21 +K23"…”

“…The appearance of radioactivity in the perfusion liquid was then kinetically followed for 15 min. Analysis of the curves of cumulative appearance of THO in the internal compartment allows for the calculation of 0 (min) according to the equation (Girard & Payan, 1977a Radioactive unloading experiments: Isotopic equilibrium was first achieved after 20 min of contact with external medium containing the same isotopic concentration as above. The appearance of radioactivity was then followed kinetically in fresh external medium and in the efferent perfusion liquid.…”

“…The appearance of radioactivity was then followed kinetically in fresh external medium and in the efferent perfusion liquid. Analysis of the curves of unloading of THO appearing in the external and internal media allows calculation of the sum of the transfer coefficients, 2 (rain-1) according to the equation (Girard & Payan, 1977a):…”

“…The development of the technique for perfusing the isolated trout head (Payan & Marry, 1975) led to the demonstration that adrenaline increased the gill permeability towards water diffusion by stimulating /~ receptors (Haywood, Isaia & Maetz, 1977). Furthermore, Girard and Payan (1977a), by adapting the isolated trout head preparation to experiments involving loading and unloading of radioactive tracers which were developed for other epithelial systems (Schoffeniels, 1957;Morel, 1958;Whittam & Guinebault, 1960;Istin, 1970), showed that the lamellar epithelium, the perfusion medium, and the external medium constitute an ionic exchange system of three compartments in series. These authors have shown that the intermediate compartment (lamellar) is limited by two barriers, the apical and basal membranes, 9 which have different permeability characteristics for Na + and C1-.…”