AJP - Cell Physiology, Vol 265, Issue 5 C1298-C1305, Copyright © 1993 by American Physiological Society
Cell-specific regulation of cytosolic aspartate aminotransferase by glucocorticoids in the rat kidney
S. Feilleux-Duche, M. Garlatti, M. Aggerbeck, M. Poyard, J. Bouguet, J. Hanoune and R. Barouki
Institut National de la Sante et de la Recherche Medicale Unite 99, Hopital Henri Mondor, Creteil, France.
The basal expression and hormonal regulation of cytosolic aspartate
aminotransferase (cAspAT) were investigated in the rat kidney. In
adrenalectomized animals, the basal activity was highest in the renal
cortex and in the inner stripe of the outer medulla (0.1-0.15 U/mg
protein). The glucocorticoid analogue dexamethasone increased cAspAT
activity about twofold in the cortex and in the inner stripe of the outer
medulla but not in the papilla. A half-maximal increase in the activity was
achieved at doses of approximately 5 micrograms/100 g body wt. The
mineralocorticoid aldosterone did not modify the cAspAT activity. The cell
specificity of the hormonal regulation was analyzed by in situ
hybridization. In untreated adrenalectomized rats, a cAspAT cRNA probe
labeled mainly the inner stripe of the outer medulla. After dexamethasone
or hydrocortisone treatment, labeling was uniformly increased in this part
of the medulla and was heterogeneously increased in the renal cortex. The
specific increase in labeling within the cortex was shown to be confined to
the distal convoluted tubule and the thick ascending limb. We conclude
that, in addition to widespread basal expression, cAspAT is regulated by
glucocorticoids in a highly cell-specific manner in the renal cortex. The
enzyme may thus participate in the increased energy metabolism elicited by
these hormones in these cells.
