The effect of the antimineralocorticoid, spironolactone on the hepatic synthesis of polar metabolites of aldosterone in male rats

Evaluation of the mRECIST and α-fetoprotein ratio for stratification of the prognosis of advanced-hepatocellular-carcinoma patients treated with sorafenib

OBJECTIVE

To compare the assessment of response and prognosis of patients to sorafenib treatment by the Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST (mRECIST), α-fetoprotein (AFP) and des-γ-carboxy prothrombin (DCP).

METHODS

Sixty-six patients with advanced hepatocellular carcinoma (HCC) treated with sorafenib were enrolled in this retrospective study. The response to treatment was evaluated by RECIST, mRECIST and changes in AFP and DCP.

RESULTS

The median survival time of all patients was 8.6 months. The median time to radiological progression was 3.3 months. The response rates [complete response (CR) + partial response (PR)] by RECIST and mRECIST were 3.0 and 9.0%, respectively, while the disease control rates [CR + PR + stable disease (SD)] were 50 and 50%, respectively. Assessment by mRECIST of overall survival provided a better stratification of the patients according to the response to treatment (p = 0.009) than RECIST (p = 0.09). Assessment of overall survival by a change in AFP ratio of ≤ 1 at 8 weeks was better than that of >1 at 8 weeks (p = 0.002). The DCP ratio was not useful for assessment of overall survival. Multivariate analysis identified mRECIST response (CR + PR + SD; p = 0.001), AFP ratio at 8 weeks (≤ 1; p = 0.046) and Child-Pugh A before treatment (p = 0.012) as significant and independent determinants of survival. The combination of AFP ratio at 8 weeks, assessment by mRECIST and Child-Pugh score before treatment allows stratification of prognosis of patients treated with sorafenib.

CONCLUSION

The combination of mRECIST and AFP ratio is useful for the assessment of prognosis of patients with advanced HCC treated with sorafenib.

18-substituted steroids--Part 17. 2 alpha-hydroxylated liver metabolites of aldosterone identified by high-field [1H]NMR spectroscopy

11 beta,18-Epoxy-2 alpha,3 alpha,18,21-tetrahydroxy-5 alpha,17 alpha- pregnan-20-one (2 alpha-hydroxy-3 alpha,5 alpha-tetrahydro-17-isoaldosterone) and its apo isomer have been identified by high-field NMR studies, supported by thermospray HPLC/MS, to be among the major polar metabolites formed from incubation of aldosterone with rat liver microsomal fraction. Indications that unreduced 2 alpha-hydroxy-aldosterone is also present among the metabolites have still to be confirmed.

18-Substituted steroids. Part 15. 6 beta-Hydroxylation of aldosterone by liver

6 beta-Hydroxyaldosterone and 6 beta-hydroxy-17-isoaldosterone, characterized by high-field NMR studies, are among the major polar metabolites formed from aldosterone by incubation with rat liver slices or microsomal fraction. It is uncertain at present whether the 17-iso product results from an enzymatic or a chemical inversion of configuration. Periodate degradation of the 6 beta-hydroxyaldosterone gave 6 beta-hydroxyaldosterone gamma-lactone, identical with a synthetic sample.

Effects of adrenalectomy and spironolactone on urinary metabolites of aldosterone in rats

The quantities and temporal sequences of appearance of aldosterone metabolites in the urine of adrenalectomized rats, and adrenalectomized rats treated with spironolactone, were compared following subcutaneous administration of a physiological dosage (0.05 microgram) of [1,2,-3H]aldosterone. Large amounts of radiometabolites were rapidly excreted during 0-1 and 1-3 h and only small quantities by 3-4 h in urine of both groups of rats. The majority of the urinary radiometabolites (70-85%) were identified by Sephadex DEAP-LH-20 chromatography as neutral metabolites of aldosterone (NMA), together with lesser quantities of acidic, sulfate, and glucuronide conjugates. Further characterization by high pressure liquid chromatography (HPLC) showed that 90% of the NMA excreted by adrenalectomized rats were polar metabolites which could be separated into at least 15 peaks eluting in regions of increasing polarity (designated A, B, C, and D). Only small quantities of unaltered [3H]aldosterone and no ring-A-reduced metabolites were excreted by the adrenalectomized rats. Spironolactone treatment caused large changes in the excretion of acidic and sulfate derivatives of aldosterone, as well as discrete alterations in the HPLC patterns of the polar NMA (particularly those metabolites in regions A and B). Such discrete changes in these metabolic pathways which occur at the same time as the hormonal actions of aldosterone in the kidney may provide further insight into understanding the biological role of aldosterone metabolism.

The effects of antimineralocorticoids on synthesis of aldosterone metabolites in target tissues

[3H]Aldosterone is transformed into several metabolites by subcellular fractions of rat kidney. 80-90% of the metabolites synthesized by nuclei and plasma membranes are 5 alpha-DHAldo and 3 alpha,5 alpha-THAldo in ratios of 1:2 and 1:1 respectively; small quantities of 3 beta,5 alpha-THAldo are also synthesized. In contrast, kidney cytosol metabolizes Aldo principally to 5 beta-reduced products with co-chromatograph with 5 beta-DHAldo and 3 alpha,5 beta-THAldo. Several polar neutral metabolites, as well as sulfate and acidic metabolites are also synthesized by the cytosol fraction. Similar 5 alpha-reduced metabolites, 5 alpha-DHAldo, 3 alpha,5 alpha-THAldo and 3 beta,5 alpha-THAldo are also synthesized when [3H]aldosterone is incubated in vitro with toad urinary bladder for 1 and 5 h. Significant quantities of 5 beta- and 20 beta-reduced products and sulfate and acidic metabolites are also synthesized. The metabolism of [3H]aldosterone in both target tissues is significantly inhibited by aldosterone antagonists. Several of the reduced metabolites of aldosterone synthesized in kidney and toad bladder possess significant mineralocorticoid activity. 5 alpha-DHAldo and 3 alpha,5 alpha-THAldo possess 1/10 and 1/30 and 3 alpha,5 beta possesses 1/80-1/100 of the antinatriuretic activity of Aldo. It is suggested that the metabolism of Aldo in its target tissues may be linked to regulation or expression of the hormone's actions.

The effects of adrenal and gonadal steroids and K+-canrenoate on the metabolism of aldosterone by rat liver microsomes

The synthesis of polar aldosterone metabolites by rat liver microsomes at physiological concentrations of aldosterone (21.5 nM), was markedly inhibited by progesterone, testosterone, corticosterone, K+-canrenoate and estradiol-17 beta. In contrast, corticosterone and estradiol-17 beta significantly increased the synthesis of reduced aldosterone metabolites by 8- and 15-fold respectively, the majority of which were 5 alpha-reduced products of aldosterone. In experiments at higher substrate (aldosterone) concentrations (20-200 microM) the synthesis of ring A-reduced aldosterone metabolites by liver microsomes followed Michaelis-Menten kinetics with a Km[app] for aldosterone of 160 microM and Vmax[app] of 12.2 nmoles/mg protein/5 min. In these experiments progesterone, testosterone and K+-canrenoate all competitively inhibited the synthesis of reduced metabolites with inhibition constants (Ki [app]) of 70, 85 and 55 microM respectively; however, corticosterone did not. In contrast, estradiol-17 beta increased the rate of synthesis of reduced products by 40%, lowering the Km[app] to 83 microM.

The metabolism of aldosterone in kidney

Slices of kidney cortex and medulla from adrenalectomized male rats metabolized aldosterone to at least 4 peaks of polar metabolites as well as reduced metabolites. The majority of the products were ring A-reduced and shown chromatographically to consist of 5 alpha-reduced metabolites; significant quantities of 5 beta-reduced metabolites were also synthesized. Approximately half of the 5 alpha-reduced products cochromatographed with 3 beta,5 alpha-THA and the remainder with 5 alpha-DHA and/or 3 alpha,5 alpha-THA. The anti-mineralocorticoids, spironolactone and progesterone, inhibited renal synthesis of 5 alpha-reduced products of aldosterone by 80%. 5 beta-Reduction was also slightly inhibited. Corticosterone slightly inhibited synthesis of the 5 alpha- and 5 beta-reduced products. Corticosterone and progesterone significantly inhibited the renal synthesis of the polar metabolites of aldosterone, but the inhibition was not significant at this dosage of spironolactone. Interestingly, the nuclei and plasma membranes were shown to be the most active fractions for these aldosterone transformations. Importantly significant quantities of 5 alpha-DHA and/or 3 alpha,5 alpha-THA, which possess 1/10 and 1/30, respectively, of the antinatriuretic activity of aldosterone, were synthesized at these subcellular locations.

The possible biological role of aldosterone metabolites

Following the incubation of aldosterone with microsomes from liver of adrenalectomized male rates, a previously unidentified polar neutral metabolite of aldosterone, designated "peak A" material, was isolated and purified using high pressure liquid chromatography. This peak A material, which contains a reduced hydroxylated metabolite of aldosterone, was shown to possess 2% to 3.5% of the mineralocorticoid activity relative to aldosterone. When bovine adrenal glomerulosa cells were incubated with peak A material (3 and 10 micrograms/ml), the binding of 125I-angiotensin II was inhibited by 20% and 36%, respectively. The mineralocorticoid activity of the six possible ring A reduced metabolites was tested. The 5 alpha-reduced metabolites were more potent than the 5 beta-, and the 3 alpha- were more potent than the 3 beta-reduced metabolites. The renal and extrarenal transformations of aldosterone to the polar and nonpolar (reduced) metabolites and their possible role in the accepted mechanism of action of aldosterone is discussed.

The role of cytochrome P-450 in the synthesis of polar metabolites of aldosterone by microsomes of male rat liver

Among the tissues of the male rat studied, the largest quantities of the neutral polar metabolites of aldosterone were synthesized by the hepatic microsomal fraction. The polar metabolites of aldosterone were separated by HPLC into six peaks. Three peaks of non-polar (reduced) metabolites were also synthesized. Synthesis of at least four of the neutral polar metabolites was induced by phenobarbital and inhibited by both CO and SKF-525A. The rates of synthesis of these metabolites, which were linear up to 5 minutes, correlated well with the concentration of cytochrome P-450 in the liver microsomes. Addition of aldosterone to the microsomal fraction caused a pronounced type I change in the cytochrome P-450 spectrum. The half maximal spectral change (KS) for aldosterone was calculated to be 8 microM. These experiments indicate that the neutral polar metabolites of aldosterone are produced by cytochrome P-450 dependent hydroxy lations.