Maki Ujiie

Abstract

Active transport via Na+, K+-ATPase plays an important role in establishing and maintaining proper ionic gradient across all mammalian cell membranes. A strict regulation of Na+, and K+ ion levels is especially important in excitable cells such as neurons and myocytes. Inhibition of the enzyme is associated with several pathological conditions and has serious detrimental effects on cerebral cortical cells. Yet the enzyme appears to be limited in amount and distribution in newborn rats. In this study, Na+, K+- ATPase expression and distribution in early postnatal rats were studied using Western Immunoblotting, cytochemistry and immunocytochemistry.

The Western blot study showed that α1, α2, α3, β1 and β2 isoforms of Na+, K+-ATPase were all present at birth. While the levels of a catalytic subunits remained relatively constant, the β subunits increased considerably during the first postnatal month. This might be associated with the additional role of β2 subunit as an adhesion molecule during neuronal development. For the cytochemical study, p-nitrophenylphosphate (p-NPP) was used as a substrate to study the subcellular and cellular distribution of Na+, K+-ATPase. The results suggested that the enzymatic reaction of Na+, K+-ATPase does not become apparent until the rats are 14 days old and its intensity increased in 21 and 28 day old rats. The ultrastructural study exhibited a p-NPP reaction in neurons and neuroglia. Localization of Na+, K+-ATPase in the developing blood-brain barrier (BBB) was also studied using cytochemical and [immunocytochmical] methods. The presence of all α subunits on the luminal surfaces of endothelial cells were detected using immunocytochemistry. The cytochemical methods, using p-NPP as a substrate, exhibited Na+, K+-ATPase on both the luminal and abluminal surfaces of the endothelial cells. More reaction was noted on the abluminal surface of the developing BBB. The newborn rat brain undergo remarkable remodeling during the first month following birth. During this period, some migrating neurons contact target cells while others undergo apoptosis. Neuroglia differentiate and increase in volume and the BBB becomes fully functional during this period. It is likely that cell-cell contact between various cell types is important in retaining the enzyme on the plasma membranes of cerebral cortical cells. The amount of Na+, K+-ATPase appears to increase considerably during the first month of postnatal development while the brain is being remodeled. Young animals might have regulatory mechanisms other than Na+, K+-ATPase to maintain cell volume and ionic balance.

LLU Discipline

Anatomy

Department

Anatomy

School

Graduate School

First Advisor

Robert L. Schultz

Second Advisor

Paul C. Engen

Third Advisor

Raymond G. Hall

Fourth Advisor

Clifford E. Herrmann

Fifth Advisor

Kenneth R. Wright

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

1998

Date (Title Page)

9-1998

Language

English

Library of Congress/MESH Subject Headings

Cerebral Cortex -- anatomy & histology; Na(+)-K(+)-Exchanging ATPase

Type

Dissertation

Page Count

viii; 131

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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