we investigated contraction to noradrenaline (na) and kc1 and sensitivity of na at the level of larger vessels (thoracic aorta and vena cava; left renal artery and left renal vein; lateral saphenous artery and lateral saphenous vein and finally central ear artery and marginal ear vein) in a model devised to mimic heart failure. the model presented here is the rabbit coronary ligation model in w...

The effects of quinidine and temperature on Na influx and contraction frequency of synchronously contracting rat myocardial cells in monolayer cultures were studied. Quinidine (10(-6) M to 10(-1) M) produced a prompt reduction in Na influx, maximum after 30 seconds of exposure, and dose-dependent along a sigmoid log dose-response curve. At 37 degrees C, Na influx (mumol/10(11) cells per sec) de...

Hypertension is more common in men and postmenopausal women than in premenopausal women, and gender differences in sensitivity to high dietary Na(+) salt have been suggested; however, the vascular mechanisms involved are unclear. We investigated whether increases in the extracellular concentration of Na(+) ([Na(+)](e)) enhance the mechanisms of vascular smooth muscle contraction and whether the...

Effects of ouabain (10-12M to 10-5M) on the simultaneously recorded transmembrane action potential and contraction; and (Na+K+)-activated membrane ATPase of human papillary muscles were investigated. Ouabain in the concentration of 10-12M did not affect the transmembrane potential, contraction and (Na+-K+)-ATPase activity. Ouabain in the concentrations of 10-11 to 10-7M produced a concentration...

To clarify the function of the Na(+)-coupled glucose transporter in the regulation of cellular tone of cultured retinal pericytes, we investigated the effects of extracellular glucose concentration on cell size. The surface area and diameter of cultured bovine retinal pericytes under different glucose concentrations were measured by using a light microscope with a digital camera. We also examin...

Vasoconstrictors activate phospholipase C (PLC), which hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP(2)), leading to calcium mobilization, protein kinase C activation, and contraction. Our aim was to investigate whether PLC-delta(1), a PLC isoform implicated in alpha(1)-adrenoreceptor signaling and the pathogenesis of hypertension, is involved in noradrenaline (NA) or endothelin (ET-1)-...

Micro-osmotic manipulation was used to determine the influence of osmotic contraction on the expansion potential of individual protoplasts isolated from rye (Secale cereale L. cv Puma) leaves. For protoplasts isolated from leaves of nonacclimated plants (NA protoplasts), osmotic contraction in sufficiently hypertonic solutions (>1.53 osmolal) predisposed the protoplasts to lysis during osmotic ...

Isolated beef heart mitochondria, swollen in 100 mM Nat or K+ nitrate, contract and extrude the accumulated salt in a respiration-dependent reaction. The reaction is more rapid and extensive in Na+ than in K+ nitrate. Contraction is inhibited by uncouplers and by reagents, such as valinomytin and gramicidin, which increase transmembrane permeability to cations. The rate and extent of contractio...

The effects of varying the sodium gradient-either by lowering [Na+]o or by increasing [Na+]i on the electromechanical properties of pregnant rat uterine smooth muscle were studied. In normal tissues, complete removal of external sodium ions (choline, Tris or sucrose as substitutes) induced a strong and maintained contraction which was dependent on the presence of extracellular calcium ions, and...