From frog skin to sheep rumen: a survey of transport of salts and water across multicellular structures

Keynes, R. D.

doi:10.1017/s0033583500001086

Cited by 136 publications

(46 citation statements)

References 332 publications

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“…However, the present work shows that maximal water absorption from the rumen usually coincided with minimal sodium (and potassium) absorption, and that sodium (and potassium) was still being absorbed at substantial rates under conditions in which water was entering the rumen across the rumen wall. Consequently, if transmural water movement, or some part of it, is linked with sodium movement, as Keynes [1969] suggested, then there must also be a mechanism for water transport independent of sodium, as suggested by Engelhardt [1969a]. In the frog skin, an organ in many ways similar to the rumen wall, it also seems that not all water movement is tightly linked to solute movement [Kirschner, Maxwell and Fleming, 1960;Schoffeneils and Tercafs, 1962] Warner and Stacy [1962] developed a thermodynamic theory showing that changes in fluid movement in response to changes in osmotic gradient would have little effect on active solute transport.…”

Section: Effect Of Rumen Solutes On Water and Electrolyte Absorptionmentioning

confidence: 99%

Water, Sodium and Potassium Movements Across the Rumen Wall of Sheep

Warner¹,

Stacy²

1972

Exp Physiol

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Saliva was entirely diverted from the rumen of sheep via an oesophageal fistula and usually replaced by infusion of a synthetic saliva of known composition. Water movements in the rumen were measured by the use of soluble markers, and sodium and potassium movements were calculated. Water and various solutions were added to the rumen to vary its osmolality over the range 180-550 m-osmole/kg. When saliva was not replaced, recovery of the normal rumen osmolality following water loading was very slow indeed. When saliva was replaced by a synthetic solution the rate of water movement across the rumen wall (y, [1./hr]) was a linear function of the osmotic pressure (x, [m-osmole/kg]), such that y = 0 404-0 001206x (r =-0 90). This suggests that the filtration permeability of the rumen wall was similar to that of frogskin or toad bladder. Potassium absorption across the rumen wall was also slow but positively related to the potassium concentration. Sodium absorption appeared to depend on the potassium concentration and the osmotic pressure as well as on the sodium concentration. While moderate levels of potassium increased the rate of sodium absorption, grossly high levels, sufficient to produce a substantial entry of water across the rumen wall, decreased it, sometimes markedly. The rate of potasium and perhaps sodium absorption seemed to depend on the immediate state of nutrition of the animal. There is some conflict of evidence and opinion on the rate of movement of water between the rumen and the blood across the rumen wall [see Warner and Stacy, 1968b; Engelhardt, 1970]. In our early work calculations of trans-epithelial water movement were usually based on assumptions about the rate of salivary secretion; sheep fitted with oesophageal fistulae, allowing actual measurement of salivation rate, were used in only a few experiments. In the present work, saliva was entirely diverted via an oesophageal fistula and replaced by a synthetic saliva solution of known composition and entry rate. The composition of the rumen contents was altered by the addition of water or solutions and the effects of these treatments on the rates of movement of water, sodium and potassium across the rumen wall were measured. METHODS Sheep and Diets. Merino ewes weighing about 35 kg and fitted with rumen and oeso-phageal cannulae were kept in metabolism crates. They were accustomed to the experimental routine. They were usually given 700 g of ground lucerne hay every morning but occasionally individual sheep refused this for a period and other rough-age diets were substituted. There was no evidence that such differences in diet had any effects on the experiment findings. Water was freely available. 103

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Section: Effect Of Rumen Solutes On Water and Electrolyte Absorptionmentioning

confidence: 99%

Water, Sodium and Potassium Movements Across the Rumen Wall of Sheep

Warner¹,

Stacy²

1972

Exp Physiol

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“…Diamond & Bossert, 1967)-which may apply to water transport in the renal cortex (e.g. de Wardener, 1969) and in a wide variety of tissues (Keynes, 1969) (Atherton et al 1968b) and water (Atherton et al 1968c) diureses.…”

Section: Potassium and Ammoniummentioning

confidence: 99%

Effects of 0·9% saline infusion on urinary and renal tissue composition in the hydropaenic, normal and hydrated conscious rat

Atherton¹,

Green²,

Thomas³

1970

The Journal of Physiology

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SUMMARY1. Changes in water and solute outputs of hydropaenic, normal and hydrated conscious rats were determined during intravenous infusion (0.2 ml./min) of isotonic (0.9 %) saline for 4 hr; renal tissue composition was determined before, and after 1 or 2 hr, infusion.2. In normal and hydrated rats increased excretion of water and sodium was such that urinary output matched intravenous input from about 2 hr. In hydropaenic rats, the diuretic and natriuretic response was much reduced; a retention of infused saline, equivalent to 15% body weight, occurred over 4 hr.3. A considerable increase in urea output and clearance, and a smaller increase in potassium and ammonium outputs, occurred in all groups.4. The corticomedullary osmolal gradients characteristic of non-diuretic rats were largely dissipated during saline infusion: by 1 hr in normal and hydrated rats, and by 2 hr in the hydropaenic group.5. These changes were ascribable mainly to an increase in tissue water content in all segments, particularly in the hydropaenic group; and to a profound decrease in urea content in all groups.6. Changes in tissue sodium content were smaller, and differed between segments and between the differently hydrated groups. A decrease in papillary content occurred in hydropaenic and normal groups and an increase in cortical and outer medullary content occurred in all groups. 7. After 2 hr saline infusion, incomplete papillary-urinary osmotic equilibration was evident in all groups.8. These changes in medullary osmolality and in papillary-urinary osmotic equilibration preceded the maximal diuresis, and must contribute to the diuresis induced by saline infusion, as in water and osmotic diureses.

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“…9). If this hypothesis is true, BSIF might be regulated by the activity of Na+, K+-ATPase, a membrane-bound enzyme that controls the transport of sodium across many other cellular membranes (12)(13)(14)(15). In support of this view, previous studies from this laboratory have demonstrated that Na+, K+-ATPase is present in fractions of liver plasma membranes that are enriched in bile canaliculi.…”

mentioning

confidence: 99%