Maintenance of the Ionic Composition of the Incubated Artery

Abstract

The ionic composition of the incubated rat tail artery, comparable but not identical to that of the freshly dissected tissue, can be maintained over a period of at least 5 h under aerobic conditions in the absence of utilizable exogenous substrate. A sufficient supply of exogenous glucose must be provided for the maintenance of this ionic composition under anaerobic conditions. The changes in the content of individual ions and water brought about by iodoacetate poisoning can be prevented more or less completely by addition of a utilizable noncarbohydrate substrate such as pyruvate or butyrate to the incubation medium. Abolition of the transmembrane ionic gradients caused by 2,4-dinitrophenol or oligomycin can be partially-prevented by exogenous glucose. The ionic composition of the artery is little affected by fluoroacetate inhibition even in the absence of utilizable exogenous substrate. The content of magnesium is decreased by 2-deoxy-D-glucose, although the content of other ions remains unchanged. Metabolic energy seems to be required to prevent the tissue calcium from rising.

Lithium Substitution and the Distribution of Sodium in the Rat Tail Artery

“…The cellular location of most, if not all, of this change was indicated not only by the constancy of the sum of Na and K, but also by the uniform uptake of Li during the wash at 2°C in both groups; therefore, the sum of monovalent ions was the same in both groups. As usual, the K values in fresh arteries were moderately higher than those in incubated vessels (5,13). An increase in tissue Na and a tendency to a decrease in K were apparent in this experiment.…”

“…It still must be shown that the value of cellular Na so defined increases in proportion to K loss following conventional Na enrichment of cells by interruption of Na transport (13).…”

“…It has repeatedly been pointed out that the transmembrane monovalent cation gradients in arterial tissue run downhill with very slight provocation; therefore, a convenient test of normality is the arterial K content. Although incubated arteries do not contain quite as much K as fresh vessels, they can certainly accumulate some 90% of the normal K complement (10,13). If this K complement is not attained, it may be anticipated that elevated values of cellular Na will be observed.…”

Evidence for enhanced sodium transport in the tail artery of the spontaneously hypertensive rat.

“…This shows that even if the tissues incubated sequentially are not optimally oxygenated, anaerobic metabolism in vascular tissue is, as reported, quite efficient. 4 It might be urged that the relatively enhanced K + uptake in the SHR in these kinetic experiments simply indicates that these vessels can more effectively recruit energy from glycolysis under the hypoxic conditions of this procedure. Against this, however, is the parallel observation of enhanced K + accumulation in fully aerobically incubated arteries in steady-state.…”

“…It may be relevant that our experiments deal with an incubated artery after prolonged incubation, while the Rb-uptake experiments have centered on the freshly excised artery from which the energy stores are presumably depleted. 4 ' 2 " Thus, the mode of activity of the Na pump which depends in large measure on the ADP-ATP ratio may differ in the two procedures. 27 ' M Finally, the Rb-uptake experiments may simply reflect the fact that hypertension exists, since similar results have been reported for both renal and DOCA hypertension.…”