AJP - Cell Physiology, Vol 258, Issue 6 C1062-C1069, Copyright © 1990 by American Physiological Society
Na(+)-K(+)-ATPase gene expression during in vitro development of rat fetal forebrain
I. Corthesy-Theulaz, A. M. Merillat, P. Honegger and B. C. Rossier
Institut de Pharmacologie, Universite de Lausanne, Switzerland.
The existence of at least three isoforms of Na(+)-K(+)-ATPase in adult
brain tissues [alpha 1, kidney type; alpha 2 [or alpha(+)]; alpha 3]
suggests that these genes might be regulated in a cell-specific and
time-dependent manner during development. We have studied this question in
serum-free aggregating cell cultures of mechanically dissociated rat fetal
telencephalon. At the protein level, the relative rate of synthesis of the
pool of alpha 1-, alpha 2-, and alpha 3-subunits increased approximately
twofold over 15 days of culture, leading to a marked increase in the
immunochemical pool of alpha-subunits as measured by a panspecific
polyclonal antibody. Concomitantly, Na(+)-K(+)-ATPase enzyme-specific
activity increased three- (lower forebrain) to sixfold (upper forebrain).
The transcripts of all three alpha-isoforms and beta-subunit were detected
in vitro in similar proportion to the level observed in vivo. alpha 3-mRNA
(3.7 kb) was more abundant than alpha 1 (3.7 kb) or alpha 2 (5.3 and 3.4
kb). Cytosine arabinoside (0.4 microM) and cholera toxin (0.1 microM) were
used to selectively eliminate glial cells or neurons, respectively. It was
found that alpha 2-mRNA is predominantly transcribed in glial cell
cultures, whereas alpha 3- and beta 1-mRNA (2.7, 2.3, and 1.8 kb) are
predominant in neuronal cultures.
