Escoubet B, Coureau C, Blot-Chabaud M, Bonvalet J P, Farman N
Institut National de la Santé et de la Recherche Médicale U246, Faculté de Médecine Xavier Bichat, Paris, France.
Am J Physiol. 1996 May;270(5 Pt 1):C1343-53. doi: 10.1152/ajpcell.1996.270.5.C1343.
Hormones can regulate the expression of their own receptor. We have examined whether adrenalectomy (ADX) and hormone replacement by physiological doses of aldosterone or dexamethasone could modulate the expression of glucocorticoid receptor (GR) or mineralocorticoid receptor (MR) at the mRNA level in the rat kidney, distal colon, and heart. Adult rats were adrenalectomized and received or did not receive an infusion of aldosterone (5 micrograms.100 g-1.day-1) or dexamethasone (10 micrograms.100 g-1.day-1). No significant change in steady-state levels of both MR and GR mRNA was detectable by using ribonuclease (RNase) protection assay (RPA) after either ADX or hormone replacement. Because the kidney is heterogeneous with regard to MR expression, RPA was adapted for measurements on microdissected nephron segments. GR mRNA is expressed at comparable levels all along the nephron, whereas MR mRNA is restricted to the distal nephron. No effect of ADX or GR and MR mRNA levels was detected in any nephron segment that was either aldosterone sensitive or insensitive. In situ hybridization confirmed the absence of corticosteroid-dependent modulation of MR mRNA in all kidney cell types. We conclude that variations of corticosteroid status do not affect MR and GR mRNA steady-state levels in heart, colon, and kidney and thus do not participate to the functional adaptations that are known to depend on hormonal status.
激素可以调节其自身受体的表达。我们研究了肾上腺切除术（ADX）以及用生理剂量的醛固酮或地塞米松进行激素替代，是否能在大鼠肾脏、远端结肠和心脏中，在mRNA水平上调节糖皮质激素受体（GR）或盐皮质激素受体（MR）的表达。成年大鼠接受肾上腺切除术，并接受或不接受醛固酮（5微克·100克⁻¹·天⁻¹）或地塞米松（10微克·100克⁻¹·天⁻¹）的输注。在肾上腺切除术或激素替代后，通过核糖核酸酶（RNase）保护分析（RPA）未检测到MR和GR mRNA稳态水平的显著变化。由于肾脏在MR表达方面具有异质性，RPA被用于对显微解剖的肾单位节段进行测量。GR mRNA在整个肾单位中以相当的水平表达，而MR mRNA局限于远端肾单位。在任何对醛固酮敏感或不敏感的肾单位节段中，均未检测到肾上腺切除术或GR和MR mRNA水平的影响。原位杂交证实，在所有肾脏细胞类型中均不存在皮质类固醇依赖的MR mRNA调节。我们得出结论，皮质类固醇状态的变化不会影响心脏、结肠和肾脏中MR和GR mRNA的稳态水平，因此不参与已知依赖于激素状态的功能适应。
