A simple mathematical model for studying mechanism-based inhibitors (MBIs) is presented. The mathematical equations are deduced for an experimental protocol consisting of a first incubation of the enzyme in the presence of MBI followed by a washing protocol to eliminate free MBI. Finally enzyme activity (initial velocity) is measured with specific substrate. The representation of the final equation obtained is a straight line, and the MBI-specific association constant of velocity (k) can be calculated from its slope. The mathematical model was then challenged with the effect of 18-ethynyl-11-deoxycorticosterone (18-EtDOC) as an MBI on aldosterone biosynthesis from 11-deoxycorticosterone (DOC) in rat adrenal mitochondria. The last step of the mitochondrial biosynthesis of aldosterone consists of the conversion of DOC into corticosterone (B) or 18-hydroxy-11-deoxycorticosterone (18-OHDOC), and both steroids can then be transformed into aldosterone. The k (mM(-1) x min(-1)) values obtained for 18-EtDOC were: 451 +/- 36 for DOC to aldosterone; 177 +/- 16 for B to aldosterone; 175 +/- 15 for 18-OHDOC to aldosterone; and 2.7 +/- 0.2 for DOC to B. These results show that this MBI practically does not affect the metabolism of DOC to B in our enzyme preparation and that conversions of B and 18-OHDOC into aldosterone are catalyzed by the same enzyme.

Los acontecimientos de un periodo historico suelen quedar objetivados en el lenguaje cotidiano con algunas palabras arquetipiticas, acunadas especialmente o resignificadas de su uso habitual. Asi, a principios del siglo XX, el vocablo internacional parecio expresar el signo de un nuevo tiempo; a mediados de la misma centuria, sin embargo, la palabra libertad quiso mostrar la necesidad de un nuevo horizonte en las perspectivas de la Humanidad. Desde la decada de los noventa existen tambien diversas expresiones con las cuales pretendemos galvanizar en un solo concepto el sentido de la historia: competencia, mercado, derechos humanos, democracia, etc. Pero hay una idea que parece llenar todos los espacios y que incluye a todas ellas. Ese termino es globalizacion, cuyo antecedente mas proximo, aunque con matices diferentes, es, precisamente, integracion. Un aspecto sustantivo de esta realidad significativa es la regionalizacion de areas con intereses comunes economicos, sociales y culturales. Este proceso de integracion entre paises se viene desarrollando hoy con diferente exito en Europa, el este asiatico, el continente americano, Oceania y Africa, en consonancia con el fenomeno de la globalizacion.

Patients with ectopic ACTH syndrome often develop hypertension and hypokalemic alkalosis with an abnormal increase in the ratio of plasma cortisol to cortisone, indicating that 11β-hydroxysteroid dehydrogenase (11βHSD) activity is inhibited. Inhibition of 11βHSD allows access of cortisol or corticosterone to the mineralocorticoid receptor where it act as a mineralocorticoid. Two isozymes, 11βHSD-1 and 11βHSD-2, have been cloned and characterized. The rat adrenal expresses the mRNAs for 11βHSD-2 and, in lesser amounts, 11βHSD-1. We investigated the effect of ACTH on the 11 11βHSD-2 activity in the rat adrenal. Rat adrenal cells zone fasciculata (ZF) were dispersed and incubated separately with increasing concentrations of ACTH for 90 min, and secretion of corticosterone (B) and 11-dehydrocorticosterone (A) in the media was measured by enzyme-linked immunoabsorbent assays (ELISA). The conversion of [3H]B to [3H]A in the presence of 0.5 mM NAD+ was evaluated in microsomes prepared from dispersed cells preincubated for 30 min with cyanoketone and metyrapone followed by incubation for 30 min with the same inhibitors, with and without 10 nM ACTH. The dispersed cells of the ZF produced significant amounts of A which increased with ACTH. The basal B/A ratio was 0.97±0.05. ACTH caused a concentration-dependent increase in the ratio of B/A with a maximum ratio of 9.58±0.20. ACTH also inhibited the conversion of [3H]B to [3H]A in microsomes in which endogenous B production was inhibited by cyanoketone and metyrapone. ACTH did not change theK m for B conversion, but theV max was reduced significantly (1.73±0.43 pmol/min. mg protein), indicating that ACTH suppressed the 11βHSD-2 in a noncompetitive fashion. Dibutyryl cyclic AMP (dcAMP) also produced a concentration-dependent increase in the B/A ratio, but various concentrations of calcium did not affect the enzyme activity. In summary, adrenal cells treated with ACTH results in a significant increase in the ratio of B/A in the ZF owing a noncompetitive inhibition of the 11βHSD-2 via the ACTH receptor.

"Mutations in the 11β-hydroxylase genes esf the dahl SS and SR rats.." Endocrine Research, 22(4), pp. 493–494

Primary cultures of calf adrenal glomerulosa cells were prelabeled for 3 days with [3H]inositol or [3H]glucosamine and stimulated with 10 nM ACTH. Labeled phosphatidylinositol (PI), polyphosphoinositides (PIP and PIP2) and a novel phosphatidylinositol-glycan (PI-glycan) were measured after separation by TLC. [3H]-Inositol labeling of PI, PIP and PIP2 increased rapidly, whereas labeling of the PI-glycan showed an initial decrease at 1 minute followed by a subsequent increase. Similar results were obtained when cells were prelabeled with [3H]glucosamine, viz. the PI-glycan label decreased at 1 min and subsequently increased. These results suggest that ACTH provokes (a) coordinated increases in the synthesis of PI, PIP, PIP2 and the PI-glycan, and (b) the increase in PI-glycan synthesis is preceded by initial decrease, presumably reflecting hydrolysis of this lipid.

Primary aldosteronism is the principal disorder of zona glomerulosa and a number of subsets have been identified: unilateral adenoma; bilateral micro- or macro-nodular hyperplasia (idiopathic aldosteronism); primary hyperplasia and aldosterone-producing carcinoma either adrenal or ectopic. The diagnostic criteria for a correct differential diagnosis of these subsets are now quite reliable and our experience is presented in detail. Unfortunately the pathogenesis of most of these forms is still poorly recognized and requires further investigation. An extreme sensitivity to angiotensin II is present in patients with idiopathic aldosteronism, and a role for adrenal renin is now being advocated. A peculiar form of hyperaldosteronism is the glucocorticoid-remediable subtype. An unusual sensitivity of aldosterone to ACTH is present in this form. A qualitative biochemical abnormality in this disorder consists of marked over-production of products of the cortisol C18-oxidation pathway, 18-hydroxycortisol and 18-oxocortisol, which are more abundant than aldosterone and 18-hydroxycorticosterone. A family with three affected sibs has been studied by our group. In other clinical situations, classical zona fasciculata mineralocorticoids [deoxycorticosterone (DOC), corticosterone and their 18-hydroxy compounds] are secreted in excess. The hypertensive diseases of this zone are rare DOC-secreting tumors and two forms of congenital adrenal hyperplasia (CAH), the 11β-hydroxylase (11-OHDS) and the 17α-hydroxylase deficiency syndromes (17-OHDS), which are identified by the presence of hypokalemia and suppressed renin activity. DOC is the only mineralocorticoid hormone (MCH) oversecreted in the 11-OHDS, while all ACTH-dependent MCH are very high in the 17-OHDS. The molecular basis of gene abnormalities of this disorder are currently under investigation, and preliminary data obtained in some of our patients are presented. Finally a syndrome of apparent mineralocorticoid excess, which is not a primary disorder of the adrenal cortex, describes the association of an unexplained hypermineralocorticoid state with a decreased rate of peripheral 11β-hydroxy dehydrogenation of cortisol to cortisone. Studies on this syndrome have led to the hypothesis that peripheral cortisol inactivation is the normal mechanism permitting specific mineralocorticoid recognition. The syndrome exists in two forms both characterized by a decreased turnover of a normal level of plasma cortisol, but in the type I variant an elevated cortisol/cortisone metabolite ratio is found, whereas in the type II variant this ratio is normal. Three patients of the latter form have recently been described by us and are shortly illustrated. A possible role of this impaired metabolism of cortisol in the pathogenesis of other forms of hypertension such as liquorice and carbenoxolone-induced hypertension has recently been suggested.