The mineralocorticoid receptor in rodent retina: ontogeny and molecular identity.
OBJECTIVE
Mineralocorticoid hormones contribute to ion-water balance in all cell types. In this study, we investigated the presence of mineralocorticoid receptors in rat and bovine ocular tissues and during retinal development.


METHODS
Isolated photoreceptors and/or intact retina, retinal pigment epithelium (RPE) cells, and ciliary body were analyzed for the expression of MR (Mineralocorticoid Receptor) using the polymerase chain reaction (PCR) technique. Since aldosterone can stimulate the expression of epithelial Na+ channels (ENaC), expression of this gene in RPE was measured under basal and aldosterone-induced level.


RESULTS
MR was expressed in rat photoreceptors and in the inner retina (inner nuclear layer and ganglion cell layer) even one day after birth, almost hundred percent identity was observed between rat retina and kidney MR gene products. The expression was also present in the RPE and in the ciliary body. ENaC gene was expressed in RPE and generated a predicted band at 520 bp following RT-PCR amplification which was 95% homology to that of ENaC mRNA from bovine kidney. The incubation of RPE cells in vitro with aldosterone increased the mRNA level of ENaC.


CONCLUSIONS
MR expression in the mammalian retina, RPE, and ciliary body extends the potential field of action for mineralocorticoid hormones. Results on RPE cells are consistent with the idea that steroid hormones may regulate the physiology of these tissues by modulating ENaC expression. This study provides new light on the potential effect of mineralocorticoid in this area of the nervous system.
Golestaneh
Nady
N
INSERM E9912, Faculté de Médecine Paris VI, Paris, France.
Picaud
Serge
S
Mirshahi
Massoud
M
D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002924:Ciliary Body / Q000254:growth & development / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000032:analysis; D004587:Electrophoresis, Agar Gel; D053503:Epithelial Sodium Channels; D005786:Gene Expression Regulation; D007668:Kidney / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000378:metabolism*; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018161:Receptors, Mineralocorticoid / Q000235:genetics* / Q000378:metabolism; D012160:Retina / Q000254:growth & development / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015222:Sodium Channels / Q000235:genetics* / Q000378:metabolism
D017931:DNA Primers; D018076:DNA, Complementary; D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D018161:Receptors, Mineralocorticoid; D015222:Sodium Channels; D000450:Aldosterone; D012313:RNA