Histochemical demonstration of (Na+ + K+)-activated ATPase activity of synaptosomes and synaptosomal membranes

Effect of high perilymphatic potassium concentration on the guinea pig vestibular sensory epithelium

The 'rupture theory' has been proposed to explain the vertiginous attack of Meniere's disease, and the high perilymphatic potassium concentration was thought to be the most important factor in this theory. In this investigation, potassium ion was introduced through the round window into the perilymphatic space in guinea pigs by means of iontophoresis, to investigate the effect of high perilymphatic potassium concentrations on the vestibular sensory epithelium, histochemically. Following the iontophoretic procedure, spontaneous nystagmus was observed, directed toward the iontophoretic side (irritative nystagmus) for the first 10 min, and then toward the unaffected side (paralytic nystagmus) for 24 h. Both these nystagmus types were quite reversible and left no morphological change in sensory cells. However, histochemical analysis revealed an increased ATPase activity during the irritative nystagmus and decreased ATPase activity during the paralytic nystagmus in the synaptic area between the hair cells and the nerve endings of the vestibular sensory epithelium on the iontophoretic side. Judging by these results, high perilymphatic potassium concentration is assumed to affect the synaptic area of the sensory epithelium, leading to reversible nystagmus.

Developmental and regional differences in the localization of Na,K-ATPase activity in the rabbit hippocampus

Regional differences in Na,K-ATPase activity, and development of Na,K-ATPase activity were examined in rabbit hippocampus using a histochemical marker of enzyme activity. Stratum lucidum of CA3/CA2, corresponding to the mossy fiber terminal field, showed high Na,K-ATPase activity compared to stratum radiatum of CA1. A significant increase in Na,K-ATPase activity was found between 8 and 15 days postnatal. Tissues with limited Na,K-ATPase activity (immature hippocampus, the mature CA1 region) appear particularly prone to seizure-like abnormalities, perhaps reflecting an inability to regulate extracellular potassium.

Quantitative localization of Na-K pump sites in the frog sacculus

The Na-K pump site distribution within the macula, perimacula, and wall epithelia of the sacculus in the frog inner ear was examined with quantitative [3H]ouabain autoradiography. Excised tissue was incubated for 10-30 min (23 degrees C) in micromolar concentrations of high specific activity [3H]ouabain (14-70 muCi ml-1, 5-15 Ci mmol-1), washed for 30 min (4 degrees C), then rapidly frozen (-175 degrees C) and processed for light and electron microscope autoradiography. Control experiments based on (1) high K+ (50 mM) in the incubation and (2) low specific activity [3H]ouabain (1 mM, 0.013-0.025 Ci mmol-1) indicated negligible nonspecific binding of the [3H]ouabain. Measurable levels of specific [3H]ouabain binding occurred in all saccular regions examined. Binding was localized to the basolateral cell membranes with no detectable binding to the apical membranes. [3H]ouabain binding across the apical-basal axis of the saccule macular epithelium was nonuniform. Binding was low in the apical region, rose to a peak in the middle two-thirds, and then fell again close to the basement membrane. Electron microscope autoradiography suggested that this peak was due to ouabain binding to nerve terminals. Denervation of the sacculus eliminated the peak in [3H]ouabain binding and quantitative grain density analysis revealed that 45% of the Na-K pumps within the saccule macula were located on the nerve terminals. Na-K pump site density per unit volume was estimated by quantitative grain density analysis and the following values were obtained (sites micron-3 X 10(3), means +/- S.E.M.): saccule macula, 1.9 +/- 0.2; saccule perimacula, 1.1 +/- 0.1; saccule wall, 2.3 +/- 0.3. Stereological analysis of conventionally fixed tissue was used to estimate overall plasma membrane surface area per unit volume (Sv). Na-K pump site densities per unit membrane area for the various regions were calculated by combining the autoradiographical and stereological data. The following values were obtained (sites micron-2 +/- 25%): saccule macula, 2500; saccule perimacula, 2500. Values for individual cells within the macula (sites micron-2 +/- 25%) were: hair cells, 3000; nerve terminals, 3000; supporting cells, 1500.

Cytochemical localization of adenosine triphosphatase and thiamine pyrophosphatase in the synapases of rat's cerebral cortex

Ultrastructural distribution of adenosine triphosphatase and thiamine pyrophosphatase in synapses of rat's cerebral cortex was studied. Adenosine triphosphatase activity in some synaptic vesicles and mitochondria, on pre- and postsynaptic membranes, as well as in the postsynaptic thickening was established. The reaction specificity was proved by means of some controls: various concentrations of ouabain, NaF, NiCl2, cysteine, substrate free medium and non-specific substrates - cocarboxylase and beta-glycerophosphate. At the thiamine pyrophatase reaction, the enzyme positive product was found on the membrane of some clear synaptic vesicles, on the singl sacs of smooth endoplasmic reticulum in the axon terminal, and bouton cell membrane. Substrate free medium, addition of cystein and substitution of orininal substrate with adenosine triphosphate and beta-glycerophosphate as controls were used. The fine structure localization of both enzymes in synaptic structures suggests their important role in the synaptic function.