Drugs online research references
J Insect Physiol. 2001 Apr;47(4-5):465-474.
Dopamine-induced epithelial K(+) and Na(+) movements in the salivary ducts of Periplaneta americana.
Lang I I, Walz B.
Department of Zoophysiology and Cell Biology, University of Potsdam, Lennestr. 7a, 14471, Potsdam, Germany
K(+)- and Na(+)-selective double-barrelled microelectrodes were used for intracellular and luminal measurements in salivary ducts of Periplaneta americana. The salivary ducts were stimulated with dopamine (10(-6) mol l(-1)). Dopamine decreased intracellular [K(+)] from 112+/-17 mmol l(-1) to 40+/-13 mmol l(-1) (n=6) and increased intracellular [Na(+)] from 22+/-19 mmol l(-1) to 92+/-4 mmol l(-1) (n=6). Luminal [K(+)] was 15+/-3 mmol l(-1) in the unstimulated salivary ducts and increased to 26+/-11 mmol l(-1) upon stimulation with dopamine (n=10). Luminal [Na(+)] was insignificantly increased from 105+/-25 mmol l(-1) to 116+/-22 mmol l(-1) (n=12) by stimulation with dopamine. The potential difference across the basolateral membrane (PD(b)) was depolarized from -65+/-6 mV to -31+/-13 mV (n=12) and the transepithelial potential difference (PD(t)) was hyperpolarized from -13+/-6 mV to -22+/-7 mV (n=22, lumen negative) upon stimulation with dopamine. The re-establishment of prestimulus values of intracellular [K(+)] and [Na(+)] and PD(b) was inhibited by basolateral addition of ouabain (10(-4) mol l(-1)). Furosemide (10(-4) mol l(-1)) in the bath inhibited the dopamine-induced increase in intracellular [Na(+)], the decrease in intracellular [K(+)] and the depolarization of PD(b). We propose a model for dopamine-stimulated ion transport in the salivary ducts involving basolateral Na(+)-K(+)-2Cl(-) cotransport and active extrusion of K(+) via the apical membrane.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11166311&dopt=Abstract [PubMed - as supplied by publisher]
Am J Physiol. 1992 Oct;263(4 Pt 1):C773-9.
Novel bumetanide-sensitive K+ transport in preimplantation mouse conceptuses.
Van Winkle LJ, Campione AL.
Department of Biochemistry, Chicago College of Osteopathic Medicine, Downers Grove, Illinois 60515.
Ouabain-resistant K+ transport activity was characterized primarily by measuring Rb+ uptake because 86Rb+ has a more convenient half-life than 42K+. Ouabain-resistant 86Rb+ uptake by mouse two-cell conceptuses and blastocysts was slowed by the K(+)-Na(+)-2Cl- cotransporter inhibitors bumetanide [inhibitory constant (Ki) = 400 nM] and furosemide (Ki approximately 10 microM), but it was insensitive to a variety of K+ channel blockers. This component of 86Rb+ transport was also inhibited by K+ and nonradioactive Rb+ and it was stimulated by Cl-. Nevertheless, neither 36Cl- nor 22Na+ uptake was inhibited by bumetanide, whereas 42K+ uptake was inhibited by both bumetanide and furosemide. Bumetanide-sensitive Rb+ transport in blastocysts had a Hill coefficient of 1.0 and a Michaelis constant value of 3.0 mM. By these criteria, preimplantation conceptuses contain a novel, bumetanide-sensitive K+ transport system that does not cotransport Cl- or Na+. Moreover, bumetanide-sensitive Rb+ uptake was 10 times faster in blastocysts when they were collapsed to expose the basal membrane of the trophectoderm to 86Rb+ in the medium. Therefore, the novel system may be located predominantly in the basal rather than in the apical membrane of the trophectoderm.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1415667&dopt=Abstract
Proc Chin Acad Med Sci Peking Union Med Coll. 1989;4(2):91-5.
Effects of gossypol on Na+, K+ transmembrane fluxes in human red cells.
Jin Y, Chen HC, Wo WH, Yang MZ, Xue SP.
The effects of gossypol-acetic acid (a male contraceptive) on transmembrane fluxes of sodium and potassium in human red cells were studied, in comparison with the effects of ouabain (an inhibitor of Na+-K+-ATPase) and furosemide (an inhibitor of Na+, K+ cotransport). It was found that gossypol may be an inhibitor of outward (Na+, K+) cotransport in human red cells but has no significant effect on (Na+, K+)-ATPase. The results provide new evidence for elucidating the mechanism of hypokalemia caused by gossypol.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2798406&dopt=Abstract
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