Effect of ouabain and potassium on ion concentrations in the choroidal epithelium

Publisher Website
Google Scholar
Abstract
Lateral ventricle choroid plexus (CP) Na+-K+ transport was investigated by measuring ouabain- (inhibition) and KCl- (stimulation) induced changes in cell [Na+] and [K+]. Adult rats were injected with either i.p. ouabain (0.01 or 10 mg/kg), i.p. KCl (4.5 mmol/kg) or intraventricular ouabain (0.25 mg/kg) 1 h prior to death. Compartmental analysis of tissue electrolytes revealed that intraventricular ouabain decreased CP K+ and increased CP Na+ content. I.p. ouabain or KCl treatment resulted in a rise in CP cell [K+]; cell [Na+] either fell (ouabain) or did not change significantly (KCl). Both i.p. drug injections produced a hyperkalemia, and intraventricular ouabain brought about a rise in CSF [K+]. For comparison, in vitro CP incubations were performed to correlate ouabain concentration with tissue K+ loss. Drug effect was observed over a concentration range of 10-6 to 10-2 M with an I50 of 10-4 M. When ouabain was presented to the apical membrane (intraventricular) or to both membranes (in vitro) of the CP, a decrease in cell K+/Na+ was observed. This is interpreted as evidence for an apical distribution of the CP Na+-K+ pump. The rise in cell K+/Na+ on i.p. treatment with ouabain or KCl may be a result of increased K+ transport out of the CSF to compensate for the acute hyperkalemia.