Tonoplast vesicles were isolated from leaf mesophyll tissue of the inducible Crassulacean acid metabolism plant Mesembryanthemum crystallinum to investigate the mechanism of vacuolar Na+ accumulation in this halophilic species. In 8-week-old plants exposed to 200 mM NaCl for 2 weeks, tonoplast H+-ATPase activity was approximately doubled compared with control plants of the same age, as determin...

The dynamics of different ionic currents shape the bursting activity of neurons and networks that control motor output. Despite being ubiquitous in all animal cells, the contribution of the Na(+)/K(+) pump current to such bursting activity has not been well studied. We used monensin, a Na(+)/H(+) antiporter, to examine the role of the pump on the bursting activity of oscillator heart interneuro...

adrenal cortex and brown adipose tissue: Crompton et al., 1978; Nicholls, 1978; Al-Shaikhaly et al., 1979), the fluxes of Ca2+, Na+ and H+ may be integrated into a cycle (Fig. l), for which evidence has been published (Crompton el al., 1976; Crompton & Heid, 1978; Nicholls & Scott, 1980). In cardiac muscle the cycle would never reach steady state, as it does in vitro, since the [Caz+] in the cy...

Nebulized amiloride has been proposed as therapy in cystic fibrosis to block Na+ hyperabsorption in airway epithelium and prevent dehydration of secretions. Patients with cystic fibrosis often have reactive airways. Bovine and canine trachea relax to amiloride in vitro, suggesting another benefit as a bronchodilator, whereas guinea pig trachea, a useful model of human airways, does not. We hypo...