AJP - Cell Physiology, Vol 262, Issue 1 C156-C163, Copyright © 1992 by American Physiological Society
Corticosteroid receptors in cells derived from rat brain microvessels: mRNA identification and aldosterone binding
N. Loffreda, P. Eldin, G. Auzou, C. Frelin and M. Claire
Institute National de la Sante et de la Recherche Medicale U. 300, Faculte de Pharmacie, Montpellier, France.
B7 is a cell clone derived from rat brain microvessels. Expression of an
amiloride-sensitive cationic channel has been recently established in these
cells. In this study, the polymerase chain reaction (PCR) was used to
amplify definite segments of mineralocorticoid and glucocorticoid receptor
mRNA in B7 cells. Aldosterone binding was also characterized. Two classes
of sites were detected. Aldosterone exhibited a high affinity for type I
sites [dissociation constant (Kd) approximately 0.3 nM] and a lower one for
type II sites (Kd approximately 20 nM). RU 28362, a highly specific
glucocorticoid agonist, did not compete for type I sites. RU 28362 and
dexamethasone were better competitors for type II sites than aldosterone.
The sedimentation coefficients of aldosterone type I and type II complexes
were approximately 9S. These characteristics are close to the one exhibited
by aldosterone type I and type II receptors in rat kidney and other target
tissues. In intact B7 cells, aldosterone binding expressed as number of
acceptor sites per cell was higher (approximately 41,000 for type II and
8,800 for type I) than in the soluble cellular extract (approximately
18,000 for type II and 1,000 for type I).
