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Biomedical subjects

F Wuytack

Publications and source records attributed to F Wuytack.

At least 145 records · Page 8Linked to original sources
PubMed1978

The calcium accumulation in a microsomal fraction from porcine coronary artery smooth muscle. A study of the heterogeneity of the fraction.

1. Microsomes prepared from the combined media and intima of pig coronary artery, take up Ca in an ATP-dependent way. This uptake is stimulated by oxalate. 2. Conditions have been determined to optimize the preparation of the microsomes in terms of their Ca accumulation activity. Careful homogenization of the tissue mince in 0.25 M sucrose by means of a Potter-Elvehjem homogenizer gives microsomal preparations with the highest specific activity for Ca accumulation. 3. Arguments are presented to support the hypothesis that, even in the absence of oxalate, Ca accumulation occurs into the lumen of the vesicles, and that these vesicles have a low Ca permeability. 4. Density gradient analysis shows that the microsomal fraction prepared from pig coronary artery media and intima is composed of vesicles that are heterogeneous in enzymatic composition. 5. Adenylate cyclase appears to be a predominantly plasma membrane-bound enzyme. Rotenone-insensitive NADH-cytochrome c reductase and choline phosphotransferase, two putative markers for internal membranes, give distinct banding patterns on on isopycnic centrifugation, indicating different intracellular localization. 6. There is a difference between the density gradient distribution pattern of Ca uptake measured in the presence or absence of oxalate. The latter coincides more closely with plasma membrane markers. The former resembles more the distribution of rotenone-insensitive NADH-cytochrome c reductase.

Animals↗
PubMed1977

A comparative study of the calcium accumulation by mitochondria and microsomes isolated from the smooth muscle of the guinea-pig taenia coli.

The calcium uptake by mitochondria and microsomes isolated from the guinea-pig taenia coli was studied at physiological Ca2+ concentrations, buffered by Ca-EGTA mixtures. The Ca accumulation by the mitochondria was measured from the difference between the amount of Ca taken up in the presence and in the absence of a specific mitochondrial inhibitor. The Ca uptake by the microsomes was determined in a solution containing oxalate and a mitochondrial inhibitor. It was calculated from the difference in Ca uptake measured with and without ATP. By using this procedure, the necessity of extensive purification of the isolated fractions was avoided. The (Ca2+) for half-maximal transport in the mitochondria is 7 X 10(-6) M. At (Ca2+) lower than 2 X 10(-7) M, Ca is taken up in an energy-dependent way. In the microsomes the apparent Km for Ca is 7 X 10(-7) m. accumulation is still stimulated by ATP at a (Ca2+) as low as 4 X 10(-8) M. The results show that the rate of Ca uptake by the cell organelles corresponding to the microsomal vesicles is sufficiently fast to explain the speed of relaxation of the taenia coli. The results also suggest that these cell organelles are more important than the mitochondria in regulating the cytoplasmic Ca concentration.

Adenosine Triphosphate↗
PubMed1975

Stimulation of 45Ca efflux from smooth muscle cells by metabolic inhibition and high K depolarization.

The characteristics of the extracellular and cellular calcium exchange in taenia coli have been studied by efflux experiments under different experimental conditions. The exchange of extracellularly bound calcium is accelerated by the presence of calcium in the external solution. If a Ca-free solution is used as washing solution, the slowly exchanging extracellular calcium also contributes appreciably to the later phase of the Ca efflux and obscures the changes of the cellular calcium exchange. There is no evidence for a Ca-Ca exchange diffusion. Most of the 45Ca bound at extracellular binding sites can be released by a 10 min exposure to 2 mM EGTA or to 10 mM La3+. This La concentration moreover largely inhibits the release of 45Ca from the cellular compartment by metabolic depletion. A release of cellular 45Ca can be induced by metabolic depletion or by K depolarization. Both procedures probably act at the same sequestering sites. However, while DNP + IAAa cts in the absence of external Ca, it is observed that K depolarization can only cause a Ca release if external Ca can enter the cells.

Adenosine Diphosphate↗
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↗