Neurosteroidogenesis in Rat Retinas
Article first published online: 23 NOV 2002
Journal of Neurochemistry
Volume 63, Issue 1, pages 86–96, July 1994
How to Cite
Guarneri, P., Guarneri, R., Cascio, C., Pavasant, P., Piccoli, F. and Papadopoulos, V. (1994), Neurosteroidogenesis in Rat Retinas. Journal of Neurochemistry, 63: 86–96. doi: 10.1046/j.1471-4159.1994.63010086.x
- Issue published online: 23 NOV 2002
- Article first published online: 23 NOV 2002
- Received September 10, 1993; revised manuscript received November 15, 1993; accepted November 22, 1993.
- P450scc enzyme;
- Cyclic AMP regulation;
- Rat retina
Abstract: Neurosteroids (steroids synthesized in the CNS) function by modulating neurotransmission. To establish an experimental model for investigation of neurosteroid synthesis and regulation, independent of blood-borne steroids, we examined the steroidogenic activity of isolated rat retinas. We identified progesterone, pregnenolone, dehydroepiandrosterone, desoxycorticosterone, 3α,5α-tetrahydrodesoxycorticosterone, 3α-hydroxy-5α-dihydroprogesterone, 17-hydroxyprogesterone, and 17-hydroxypregnenolone together with their esterified forms. As pregnenolone is the precursor of all steroids, its formation was studied in detail as an index of a steroid-synthesizing tissue. Pregnenolone was identified further by gas chromatography coupled to mass spectrometry, and its in vitro synthesis was inhibited by lovastatin, an inhibitor of mevalonolactone and cholesterol biosynthesis. We then examined pregnenolone synthesis in the presence of mevalonolactone as a precursor of sterol formation together with lovastatin, which reduces endogenous mevalonolactone synthesis, as well as with inhibitors of pregnenolone metabolism. The incorporation of mevalonolactone into pregnenolone and its sulfate ester was time- and concentration-dependent and blocked by aminoglutethimide, a competitive inhibitor of cytochrome P450 side-chain cleavage (P450scc) enzyme. Immunocytochemical studies with a specific antibody to P450scc revealed a primary localization of the enzyme at the retinal ganglion cell layer. A less pronounced immunostaining was also seen at cells of the inner nuclear layer. Compounds known to stimulate cyclic AMP content also stimulated pregnenolone formation by rat retinas. These results demonstrate that rat retinas synthesize steroids and, for the first time, they reveal the steroidogenic ability of neuronal cells. We propose rat retinas as an in vitro model system to study neurosteroidogenesis in the CNS.