Modern biochemical methods for the diagnostics of pheochromocytoma

The objective of the present work was to estimate the possibility of using the ELISA technique for the quantitative analysis of the metanephrine and normetanephrine levels in urine and to determine the cross-off points for the discrimination between their normal and pathological values for the purpose of diagnostics of pheochromocytoma. Methylated derivatives of adrenaline and noradrenaline were measured in 3,234 urine sample obtained from the patients presenting with elevated arterial pressure, resistance to therapy, and adrenal mass lesions who had visited the inpatient and outpatient departments of the Endocrinological Research Centre during the past 4 years. The measurement of total metanephrine and normetanephrine (free plus deconjugated fractions) was performed using commercial ELISA kits (IBL, Hambutg, Germany). The content of normetanephrine over 612 mcg in daily urine samples was shown to be the borderline between the normal values and those suggesting diagnosis of pheochromocytoma. The sensitivity of this assay was 97,5% (95% CI 91,1-99,6%), specificity 100% (95% CI 93,8-100%). For metanephrine, the level of more than 550 mcg/24 hours was the borderline between the normal values and those suggesting diagnosis of pheochromocytoma. The sensitivity of the method was 100% (95% CI 88-100%), specificity - 96% (95% CI 86-99,4%). The biochemical diagnosis of pheochromocytoma was confirmed by the reference pathomorphological method in 99% of the cases. The incidence of pheochromocytoma predicted by the biochemical analysis of the urine samples delivered to the laboratory during 4 years from the patients with the tentative diagnosis of this pathology (based on the elevated arterial pressure and the presence of adrenal mass lesions) was 4% on the average. It is concluded that the application of ELISA in a "manual" mode provides high sensitivity and specificity of quantitative determination of metanephrines in daily urine comparable to those achieved with the widely used but more expensive high performance liquid chromatography.

Prenatal glucocorticoid exposure in the sheep alters renal development in utero: implications for adult renal function and blood pressure control

Treatment of the pregnant ewe with glucocorticoids early in pregnancy results in offspring with hypertension. This study examined whether glucocorticoids can reduce nephron formation or alter gene expression for sodium channels in the late gestation fetus. Sodium channel expression was also examined in 2-mo-old lambs, while arterial pressure and renal function was examined in adult female offspring before and during 6 wk of increased dietary salt intake. Pregnant ewes were treated with saline (SAL), dexamethasone (DEX; 0.48 mg/h) or cortisol (CORT; 5 mg/h) over days 26–28 of gestation (term = 150 days). At 140 days of gestation, glomerular number in CORT and DEX animals was 40 and 25% less, respectively, compared with SAL controls. Real-time PCR showed greater gene expression for the epithelial sodium channel (α-, β-, γ-subunits) and Na+-K+-ATPase (α-, β-, γ-subunits) in both the DEX and CORT group fetal kidneys compared with the SAL group with some of these changes persisting in 2-mo-old female offspring. In adulthood, sheep treated with dexamethasone or cortisol in utero had elevated arterial pressure and an apparent increase in single nephron glomerular filtration rate, but global renal hemodynamics and excretory function were normal and arterial pressure was not salt sensitive. Our findings show that the nephron-deficit in sheep exposed to glucocorticoids in utero is acquired before birth, so it is a potential cause, rather than a consequence, of their elevated arterial pressure in adulthood. Upregulation of sodium channels in these animals could provide a mechanistic link to sustained increases in arterial pressure in cortisol- and dexamethasone-exposed sheep, since it would be expected to promote salt and water retention during the postnatal period.

"Intrauterine programming" of hormonal and metabolic processes and intrauterine growth retardation syndrome

According to the "intrauterine programming" hypothesis, the fetus responses to nutritional deficiency by adaptation in the form of long-standing changes of metabolism that eventually create predisposition to cardiovascular, metabolic, and endocrine diseases. Up to now, a wealth of catamnestic data have been gathered indicating that individuals having the history of growth retardation in the prenatal period are likely to develop a variety of hormonal and metabolic disorders when they reach their mature age. Specifically, there is the close relationship between the intrauterine growth retardation syndrome and elevated arterial pressure, impaired glucose tolerance, and metabolic syndrome. The present review summarizes the results of epidemiological and experimental studies that confirm the above hypothesis.

Aldosterone receptor antagonism alleviates proteinuria, but not malignant hypertension, in Cyp1a1-Ren2 transgenic rats

The contribution of elevated aldosterone to the pathogenesis of malignant, ANG II-dependent hypertension remains uncertain. Therefore, we examined whether chronic mineralocorticoid receptor blockade attenuates the development of malignant hypertension in transgenic rats (TGRs) with inducible expression of the Ren2 gene [TGR(Cyp1a1Ren2)]. Systolic blood pressure (SBP) was measured by radiotelemetry in male TGRs in three groups: 1) control ( n = 9), 2) hypertensives (HT; n = 8), and 3) hypertensives + spironolactone (11 mg·kg−1·day−1 sc; HTS; n = 8). Malignant hypertension was induced with dietary indole-3-carbinol (0.3%) for 10 days. Metabolic measurements were taken at the beginning of the study and at days 2 and 9. HT exhibited elevated SBP (125 ± 3 vs. 187 ± 5 mmHg), plasma renin activity (5 ± 1 vs. 29 ± 10 ng ANG I·ml−1·h−1), plasma ANG II (175 ± 39 vs. 611 ± 74 fmol/ml), and plasma aldosterone (0.31 ± 0.04 vs. 5.42 ± 1.02 nmol/l). Urinary aldosterone excretion increased 5.5-fold by day 2 and an additional 90% by day 9. HT was associated with a 1.8-fold increase in proteinuria by day 9 that was alleviated by treatment with spironolactone (25 ± 5 vs. 13 ± 3 mg/day), suggesting that aldosterone contributes to the renal damage observed in malignant hypertension. Urinary Na+ excretion was decreased 76% on day 2, despite a sixfold increase in urinary aldosterone excretion. Decrease in urinary Na+ excretion on day 2 in HT suggests that Na+ reabsorption was increased in response to the increase in aldosterone; however, the lack of a change in SBP between HT and HTS suggests that mechanisms independent of aldosterone stimulation make a greater contribution to the maintenance of elevated arterial pressure in malignant hypertension in Cyp1a1-Ren2 transgenic rats.