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Biomedical subjects

R Casteels

Publications and source records attributed to R Casteels.

At least 199 records · Page 11Linked to original sources
PubMed1975

Aerobic and anaerobic metabolism in smooth muscle cells of taenia coli in relation to active ion transport.

1. The O2 consumption and lactic acid production of the guinea-pig's taenia coli have been studied in relation to the active Na-K transport, in order to estimate the ratio: active Na extrusion/active K uptake/ATP hydrolysis. 2. By applying different procedures of partial metabolic ingibition, it was found that a reactivation of the active Na-K transport in K-depleted tissues could occur in an anaerobic medium, provided glucose was present and in an aerobic medium free of added metabolizable substrate. The active Na-K transport was rapidly blocked in an anaerobic-substrate free medium. 3. Readmission of K to K-depleted tissues under aerobic conditions stimulates both O2 consumption and lactic acid production. While the O2 consumption creeps up slowly and requires 50 min to reach control values, the aerobic lactic acid production increases to a maximum within 10 min and decreases again during the next 50 min to its steady-state value. 4. A reactivation of the Na-pump in K-depleted cells in a N2-glucose medium causes an immediate increase of the lactic acid production, which decreases to its control value after 60 min. The maximal increase in anaerobic lactic acid production during reactivation of the Na-K pump is a function of [K]O. The system can be cescribed with first order kinetics having a Vmax = 0-72 mumole.g-1 f. wt. min-1 and a Km = 1-1 mM. 5. By varying the glucose concentration of [K]O during reactivation of the Na-K pump, different Na-K pumping rates can be obtained. The ratios net Na extrusion/ATP or net K accumulation/ATP amount to -1-32 +/- 0-19 (36) and 1-02 +/- 0-11 (36), in the experiments with different glucose concentrations. Taking into account the interference by net passive fluxes, one can estimate a ratio:active Na transport/active K transport/ATP, of 1-7/0-8/1. This ratio is not very different from the values observed in other tissues.

Adenosine Triphosphate↗
PubMed1973

Effect of sodium and sodium-substitutes on the active ion transport and on the membrane potential of smooth muscle cells.

1. The changes of the ion content and of the membrane potential of taenia coli cells have been studied during prolonged exposure to Na-deficient solutions containing either Li or choline.2. A K-free solution containing either 71 mM-Na-71 mM-Li or 71 mM-Na-71 mM choline causes a slower loss of cellular K than a 142 mM-Na solution. In both these Na-deficient solutions the membrane hyperpolarizes to about -100 mV for periods up to 6 hr. This hyperpolarization is partially abolished by 2 x 10(-5)M ouabain.3. Replacing all extracellular Na by Li and maintaining 5.9 mM-K causes a fast loss of all Na and a progressive replacement of K by Li. These changes of the intracellular ion content are accompanied by a depolarization of the cells, suggesting that intracellular Li cannot substitute for Na in activating the ion pump.4. Exposing K-depleted cells to a K-free 71 mM-Na-71 mM-Li solution results in a ouabain sensitive transport of Na and Li against their electro-chemical gradient.5. The K-uptake by K-depleted cells from a solution containing 0.59 mM-K is increased by reducing [Na](o) to half of its normal value. This finding indicates that external Na inhibits the active Na-K exchange.6. In Na-enriched tissues half of the Na efflux is due to a ouabain insensitive Na-exchange diffusion. If Li is used as a Na substitute, the Na-Li exchange compensates for the diminution of the Na-exchange diffusion unless ouabain is added.

Animals↗