Extracellular space in some isolated tissues

Abstract

1. The spaces occupied by isotopically labelled inulin, polyethylene glycol, mol. wt. 4000 (PEG 4000), polyethylene glycol, mol. wt. 1000 (PEG 1000) and sucrose in metabolizing mammalian kidney and liver slices and in toad bladder epithelial cell preparations incubated in vitro have been examined. 2. In slices of mammalian tissue, and in homogenized liver, it proved impossible to extract inulin completely from tissue which had been dried. However, inulin was recovered as completely from both dried and undried toad bladder epithelial cells scraped from hemibladders incubated in vitro. 3. PEG 4000 occupied a space in all preparations similar to that from which inulin was extracted in dried tissue. 4. PEG 1000 and sucrose entered cellular water in mammalian slices, but PEG 1000 occupied a similar space to inulin in toad bladder epithelial cell preparations. 6. It is concluded that inulin enters cellular water in mammalian slices from which after drying of the slices it cannot be extracted. It thus rather fortuitously provides a measure of extracellular water under these conditions. In preparations of toad bladder epithelial cells inulin seems to be a satisfactory extracellular marker. PEG 4000, which did not appear to enter cellular water also allows a reasonable estimate of extracellular water. PEG 1000 is a suitable extracellular marker for toad bladder epithelial cell preparations but not for mammalian slices. Sucrose entered cellular water in both slices and toad bladder epithelial cells and is not a satisfactory extracellular marker in these tissues.

Volume adjustment by renal medullary cells in hypo‐ and hyperosmolal solutions containing permeant and impermeant solutes.

“…In the previous paper (Law, 1975) the problem of identifying the inulin space with ECS in medullary slices was discussed; sucrose spaces in excess of inulin spaces suggests considerable cellular penetration by sucrose. McIver & Macknight (1974) have stated the case for the gradual cellular penetration of inulin under in vitro conditions, and it is probable that the higher sucrose spaces obtained here and by the authors cited above simply reflect a greater degree of leakiness towards the smaller molecule. The quantitative discrepancy between the spaces merits comment.…”

Effects of replacing medium sodium by choline, caesium, or rubidium, on water and ion contents of renal cortical slices

“…Tissue water contents are expressed in kg water/kg tissue dry wt., and ion contents are presented in m-mole/kg tissue dry wt. Cellular water and ion contents presented in the text for slices transferred from sodium to choline Ringer were calculated assuming that the extracellular space comprises 34 % tissue water (McIver & Macknight, 1974 In all three species tissue water and chloride contents remained constant in sodium Ringer under control aerobic conditions and also with ouabain; though ouabain caused a substantial gain in sodium and loss of potassium.…”

Oxygen Consumptions and Potassium Contents of Slices of Rat Renal Cortex

“…The dried tissue was extracted with 10 ml of 0-1 m.1-' HNO3 and the sodium and potassium concentrations and the chloride concentration in the extract were determined using an EEL flame photometer and an Aminco chloride titrator respectively with external standards dissolved in 01 M HNO3. Extracellular space was estimated using ('4C) inulin extracted from dried tissue [McIver and Macknight, 1974] …”