WATER AND ION METABOLISM IN PLACENTA (III): Net movement of water, monovalent and divalent cations in slices from rabbit placenta, at different periods of gestation, incubated under metabolically favorable conditions

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Abstract
Rabbit placenta slices incubated at 38°C in oxygenated medium, in the presence of endogenous substrates + 5 mM glucose, after a period of preincubation of 120 min at 0–1°C, show a net accumulation of potassium and extrusion of water, sodium and calcium. The movement of potassium, sodium and calcium appears to be related to the rate of oxygen consumption of the slices and to be inversely proportional to the age of the tissue. The efficiency of cations movement is also dependent on the nature and composition of the incubation medium. In this respect the potassium concentration of the medium plays a major role. The movement of water, on the other hand, seems to be completely independent from both the rate of respiration and the age of the tissue. The results are discussed in terms of relation between placenta age and senescence, and efficiency of the mechanisms devoted to the cell regulation of water and ions content.