RESUMEN
We have evaluated the metabolism of radiolabeled progesterone (P) by the microsomal fraction isolated from HaCaT keratinocytes. P was widely metabolized to different compounds that included DOC (5-7% conversion) thus demonstrated 21-hydroxylase (21-OHase) activity, a key step in adrenal synthesis of gluco- and mineralocorticoids. However, RT-PCR amplification for the CYPc21 transcript of the corresponding gene showed no evidence for gene expression in HaCaT cells suggesting that the 21-OHase enzyme present in keratinocytes is different from that described in adrenal gland. Further characterization showed that whereas estradiol stimulated markedly P metabolism by HaCaT microsomes, with generation of new unidentified compounds, Lineweaver-Burk analysis of keratinocyte 21-OHase activity showed that the K(m) and V(max) were unaffected by estrogen. The apparent K(m) was 0.6 microM without estradiol and 0.7 microM with estradiol, while the respective V(max) values were 60 and 76 nmol/l/min. To conclude, we found extensive metabolism of P in human keratinocytes, we also provide the first demonstration of 21-OHase activity in this cell system and further showed that it is coded by a gene different from the adrenal CYPc21.
Asunto(s)
Queratinocitos/metabolismo , Piel/metabolismo , Esteroide 21-Hidroxilasa/metabolismo , Glándulas Suprarrenales/metabolismo , Línea Celular , Células Cultivadas , Cromatografía en Capa Delgada , Desoxicorticosterona/metabolismo , Estrógenos/metabolismo , Humanos , Cinética , Microsomas/metabolismo , Reacción en Cadena de la Polimerasa , Progesterona/metabolismo , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
UNLABELLED: Aldosterone producing adenoma (APA) is a rare but potentially curable form of paediatric hypertension. We report a case of APA in a 9-year-old boy, suspected due to persistent hypokalaemia. Neither BP nor initial laboratory investigations disclosed the diagnosis and the presence of an APA was suggested by functional tests and radiological findings. Histologically, a cortical tumour was found associated with a marked medullary hyperplasia of both chromaffin and ganglion cells. CONCLUSION: This case reinforces the need for further investigations in patients with misleading clinical and laboratory data.
Asunto(s)
Adenoma/complicaciones , Neoplasias de las Glándulas Suprarrenales/complicaciones , Hiperaldosteronismo/etiología , Adenoma/patología , Neoplasias de las Glándulas Suprarrenales/patología , Médula Suprarrenal/patología , Niño , Humanos , Hiperplasia , Hipertensión Renal/etiología , Hipopotasemia/etiología , MasculinoRESUMEN
In the kidney, the 11beta-hydroxysteroid dehydrogenase type 2 enzyme (11betaHSD2) inactivates glucocorticoids to their inactive ketoforms and thus prevents endogenous glucocorticoids from occupying the nonselective mineralocorticoid receptor in epithelial tissues. Several mutations have been described in the 11betaHSD2 gene in the congenital syndrome of apparent mineralocorticoid excess. These mutations generate partially or completely inactive 11betaHSD2 enzymes. In the present work, we describe an already known mutation in a new patient affected by apparent mineralocorticoid excess, which results in an arginine-to-cysteine mutation (R213C) in the 11betaHSD2 enzyme. This mutation has been found in two other independent families. In vitro expression studies of this mutant provide evidence that the mutant protein is normally expressed, but its activity is abolished. The CGC-to-TGC (C-toT) transition at codon 213 can be considered a typical CpG-consequence mutation. The present finding suggests that the codon R213 of 11betaHSD2 is a hot spot for mutations in this gene, as shown by the occurrence of an R213C point-mutation in several families unrelated to each other.