Rabbits were infused with 3.7 GBq (100 mCi) of [24Na]Na ion in a 100-ml sodium carbonate solution. Beta particles were detected using a Tennelec Counting System; background counts were 1.6 +/- 1 counts per minute (cpm). Counts for one nanoliter of blood ranged from 22 to 30 cpm. Blood volumes on the mouthparts of tabanids following a 15-sec interrupted feeding were estimated to be 12.5 nl for T...

The effects of insulin and glucagon on the (Na+-K+)-ATPase transport activity in freshly isolated rat hepatocytes were investigated by measuring the ouabain-sensitive, active uptake of 86Rb+. The active uptake of 86Rb+ was increased by 18% (p less than 0.05) in the presence of 100 nM insulin, and by 28% (p less than 0.005) in the presence of nM glucagon. These effects were detected as early as ...

Synergistic effects of Ca2+-mediated secretagogues and cyclic AMP-mediated secretagogues on Cl- secretion by guinea pig distal colon were studied in vitro using Ussing chambers. Short-circuit current (Isc) and bidirectional fluxes of 22Na+ and 36Cl- were measured. Bethanechol (10(-4) M, a Ca2+-mediated secretagogue) caused an increase in Isc, which was enhanced 4-20 fold when the tissue was pre...

Reduced gastrointestinal HCO3- secretion contributes to malabsorption and obstructive syndromes in cystic fibrosis. The apical HCO3- transport pathways in these organs have not been defined. We therefore assessed the involvement of apical Cl-/HCO3- exchangers and anion conductances in basal and cAMP-stimulated duodenal HCO3- secretion. Muscle-stripped rat and rabbit proximal duodena were mounte...

The Na+ transport pathways of normal rat thymocytes were investigated. Na+ conductance was found to be lower than K+ conductance, which is consistent with reported values of membrane potential. In contrast, the isotopically measured Na+ permeability was greater than 10-fold higher than that of K+, which indicates that most of the flux is electroneutral. Cotransport with Cl- (or K+ and Cl-) and ...

Prostaglandins stimulate repair of the ischemia-injured intestinal barrier in the porcine ileum through a mechanism involving cAMP-dependent Cl- secretion and inhibition of electroneutral Na+/H+ exchanger (NHE) activity. In the present study, we focused on the role of individual NHE isoforms in the recovery of barrier function. Ischemia-injured porcine ileal mucosa was mounted on Ussing chamber...

The possible role of Na+ in the development of hypertension in rats was explored in measurements of intracellular Na+, 22Na efflux, and 3H-ouabain binding sites in resistance vessels and skeletal muscles. In resistance vessels obtained from 13-week-old spontaneously hypertensive rats (SHR) or age-matched Wistar-Kyoto rats (WKY), (Na)i, total or ouabain-resistant 22Na efflux, and the concentrati...

1. The effect of unsaturated long-chain non-esterified fatty acids (NEFA) on the human leucocyte sodiumpump was studied in vivo. 2. Plasma NEFA level was raised acutely from 0.28 (SD 0.10) to 2.54 (SD 0.48) mmol/l by infusion of 'Intralipid 20%' (trademark) at 90 ml/h with heparin, and the human leucocyte 22Na efflux rate constants were studied in eight normal weight males. 3. After 3 h, there ...

The exchange (release resp. uptake) of K+, Rb+, and Na+ ions in the isolated retina of the crayfish Astacus leptodactylus with the surrounding medium was measured using flame photometry and radioisotopic techniques. 1. The net release of K+ into a Na+ and K+ free, choline containing medium, as measured by means of flame photometry, is increased by illumination. 2. The release of 86Rb+, used as ...

The prokaryotic V-ATPase of Enterococcus hirae, closely related to the eukaryotic enzymes, provides a unique opportunity to study the ion-translocation mechanism because it transports Na(+), which can be detected by radioisotope (22Na(+)) experiments and X-ray crystallography. In this study, we demonstrated that the binding affinity of the rotor ring (K ring) for 22Na(+) decreased approximately...