RESUMEN
A radioimmunological method for the sensitive estimation of plasma corticotropin immunoreactivity (ACTH) using commercially available reagents is presented. The method involves silica extraction of corticotropin from plasma, desorption with acid protein solution, neutralization and subsequent radiomimmunoassay (RIA). [125I]corticotropin is added as internal standard to the plasma sample. The amounts of corticotropin extractable with silica differed considerably between the plasma samples of individual subjects. There were marked differences in the affinity of five different corticotropin standards to the antiserum used. The detection limit of the method was found to be 1.47 pmol/l. Blanks arising in water and in charcoal stripped serum were lower than the detection limit. Precision and accuracy were within the range commonly achieved for RIA-methods. Morning levels of normal subjects ranged from 6.5-10.9-18.5 pmol/l. Hydrocortisone infusion suppressed plasma corticotropin from 12.6 +/- 6.4 (S.D.) to 4.4 +/- 3.1 (S.D.) pmol/l. Infusion of metyrapone increased corticotropin levels from 7.3 +/- 4.2 (S.D.) to 15.3 +/- 6.0 (S.D.) pmol/l.
Asunto(s)
Hormona Adrenocorticotrópica/sangre , Radioinmunoensayo/métodos , Humanos , Hidrocortisona/análogos & derivados , Hidrocortisona/farmacología , Indicadores y Reactivos , Masculino , Metirapona/farmacología , Hipófisis/efectos de los fármacos , Hipófisis/metabolismoRESUMEN
The in vivo influence of metyrapone (M) on different adrenal enzymes has been studied by simultaneous measurement of serum progesterone (P), 17-hydroxyprogesterone (17-OHP), deoxycorticosterone (DOC), corticosterone (B), deoxycortisol (S), 18-hydroxydeoxycorticosterone (18-OHDOC), aldosterone and cortisol (F) as well as by the measurement of plasma ACTH before and after oral administration of 40 mg of M/kg at 08:15 in four healthy male subjects. The well known inhibitory effect of M on adrenal 11-hydroxylase is demonstrated by a decrease of serum F and B and synchronous increase of serum S and DOC after administration of M. The additional inhibition of 18-hydroxylase by M is documented by a decrease of serum 18-OHDOC in spite of a marked increase of serum DOC after M. The moderate increase of serum P and 17-OHP soon after drug administration, although plasma ACTH is highly elevated at this time, as well as the marked increase of these steroids in the afternoon synchronously to a rise of serum F and B suggest a further inhibitory effect of M on the enzyme prior to the total corticosteroid biosynthesis. This effect of M should be taken into account if ACTH activity is monitored in terms of adrenal steroid output in the metyrapone test.
Asunto(s)
Corticoesteroides/sangre , Hormona Adrenocorticotrópica/sangre , Metirapona/farmacología , Corteza Suprarrenal/efectos de los fármacos , Corteza Suprarrenal/enzimología , Adulto , Aldosterona/sangre , Corticosterona/sangre , Cortodoxona/sangre , Desoxicorticosterona/sangre , Humanos , Hidrocortisona/sangre , Hidroxiprogesteronas/sangre , Cinética , Masculino , Hipófisis/efectos de los fármacos , Progesterona/sangre , Esteroide 11-beta-Hidroxilasa/metabolismoRESUMEN
The influence of metyrapone (M) on the adrenal 18-hydroxylation was studied in two groups of healthy young men. In group I, serum concentrations of 18-OH-11-deoxycorticosterone (18-OH-DOC) fell significantly after a single oral dose of 40 mg/kg of M at 8.00 h, while those of 11-deoxycorticosterone (DOC) increased by a factor of about 500 within 4 hours after drug administration. Serum concentrations of 18-OH-DOC remained suppressed up to 14,00 h and tended to increase up to 16.00 h with a concomitant increase of plasma ACTH. In group II, serum concentrations of 18-OH-DOC and corticosterone (B) were slightly lowered eight hours after oral administration of 30 mg/kg of M at midnight in comparison with measurement of the previous day. Serum concentrations of 11-deoxycortisol (S) and DOC were markedly increased after drug administration. These findings indicate an inhibitory effect of M on adrenal 18-hydroxylation in addition to 11-hydroxylation under in vivo conditions. The slight increase of 18-OH-DOC at 16.00 h in group I and the only slight decrease of this steroid 8 hrs after drug administration in group II may be explained by declining enzyme blockade and a superimposed ACTH stimulation of the adrenal cortex at this time.