ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: Na+,K+-ATPase concentration in rat cerebral cortex was studied by vanadate-facilitated [3H]ouabain binding to intact samples and by K+-dependent 3-O-methylfluorescein phosphatase activity determinations in crude homogenates. Methodological errors of both methods were evaluated. [3H]Ouabain binding to cerebral cortex obtained from 12-week-old rats measured incubating samples in buffer containing [3H]ouabain, and ouabain at a final concentration of 1 × 10–6 mol/L gave a value of 11,351 ± 177 (n = 5) pmol/g wet weight (mean ± SEM) without any significant variation between the lobes. Evaluation of affinity for ouabain was in agreement with a heterogeneous population of [3H]ouabain binding sites. K+-dependent 3-O-methylfluorescein phosphatase activity in crude cerebral homogenates of age-matched rats was 7.24 ± 0.14 (n = 5) μmol/min/g wet weight, corresponding to a Na+,K+-ATPase concentration of 12,209 ± 236 pmol/g wet weight. It was concluded that the present methods were suitable for quantitative studies of cerebral cortex Na+,K+-ATPase. The concentration of rat cerebral cortex Na+,K+-ATPase showed ∼10-fold increase within the first 4 weeks of life to reach a plateau of ∼11,000–12,000 pmol/g wet weight, indicating a larger synthesis of Na+,K+ pumps than tissue mass in rat cerebral cortex during the first 4 weeks of development. K+ depletion induced by K+-deficient fodder for 2 weeks resulted in a slight tendency toward a reduction in K+ content (6%, p 〉 0.5) and Na+,K+-ATPase concentration (3%, p 〉 0.4) in cerebral cortex, whereas soleus muscle K+ content and Na+,K+-ATPase concentration were decreased by 30 (p 〈 0.02) and 32% (p 〈 0.001), respectively. Hence, during K+ depletion, cerebral cortex can maintain almost normal K+ homeostasis, whereas K+ as well as Na+,K+ pumps are lost from skeletal muscles.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1992.tb10100.x
Permalink
