Stanley W. Dziedzic

Plasma catecholamines in hypertension and pheochromocytoma determined using ion-pair reversed-phase chromatography with amperometric detection : Investigation of the separation mechanism and clinical methodology

The retention behavior of catecholamines (CAs) in ion-pair reversed-phase chromatography is examined. From the effects of pH, ionic strength and a secondary ion-pairing reagent (citric acid), under our chromatographic conditions, the retention behavior can be explained by assuming a mixed ion-exchange mechanism with octyl sulfate and citrate, on the column and in the mobile phase, respectively. The developed separation method was applied to the analysis of CAs in plasma samples purified by alumina adsorption and detected amperometrically. This method provides the basis for the determination of the short-term magnitude of CA response to physical and physiological interventions, as well as the baseline CA levels in essential hypertension and pheochromocytoma. The results seen for norepinephrine and epinephrine are consistent with eh funcitonal roles of these CAs as hormones or peripheral transmitters.

Diagnosis of neuroblastoma by qualitative and quantitative determination of catecholamine metabolites in urine

Neuroblastoma, one of the most common solid malignant tumors of childhood, has been frequently confused with other malignancies as well as nonneoplastic diseases. The observation that neural crest tumors resulted in excretion of elevated quantities of the catecholamines and their by‐products opened the way for development of biochemical techniques for their detection. Vanillylmandelic acid, metanephrines, homovanillic acid, and 3‐methoxy‐4‐hydroxy‐phenylethyleneglycol excretions of 180 normal children were compared with those of 62 subjects suffering from illnesses commonly confused with neuroblastoma as well as 41 patients with neural crest lesions. A simple, bedside chemical technique for detecting a neuroblastoma resulted in no false positive and 91% reliability among those patients with this tumor. Although quantitative assay for 3‐methoxy‐4‐hydroxyphenylethyleneglycol appeared to offer the greatest reliability for biochemical diagnosis of neuroblastoma, broad application of the screening test might significantly improve the ease of detection and differential diagnosis of neuroblastoma.

A gas-liquid chromatographic method for the separation and quantitation of normetanephrine and metanephrine in human urine

Abstract A gas-liquid Chromatographic method for the separation and quantitation of urinary normetanephrine and metanephrine as their trifluoroacetyl derivatives is presented. After a preliminary column separation of basic from neutral and acidic compounds in hydrolyzed urine, the trifluoroacetylated amines (normetanephrine, metanephrine, octopamine, tyramine, 3-methoxytyramine, tryptamine and serotonin) were separated on a 1:1 w/w (3% QF-1: 2% XF-1105) column. An electron capture detection system was employed for maximal sensitivity. Normal human urinary values for normetanephrine ranged from 0.086 to 0.177 μg/mg creatinine (mean = 0.116 ± 0.029) and for metanephrine ranged from 0.059 to 0.145 μg/mg creatinine (mean = 0.093 ± 0.027). Patients with pheochromocytoma and neuroblastoma had elevated urinary excretions of normetanephrine and/or metanephrine.

Persistence of abnormal REM sleep response to ethanol as a result of previous ethanol ingestion

Ethanol was administered to Sprague-Dawley rats for 4–6 weeks following which these animals thrived in a manner comparable to a naive control group. Over 6 months after an ethanol-free interval, the alcohol-exposed animals responded to a test dose of ethanol with a greater disturbance in REM sleep than noted in the naive group.

Quantitative determination of 3-methoxy-4-hydroxyphenylethyleneglycol and its sulfate conjugate in human lumbar cerebrospinal fluid using liquid chromatography with amperometric detection

A sensitive and direct reversed-phase liquid chromatographic method with amperometric detection was developed for the determination of 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG). The concentrations of the free and sulfate conjugate of MHPG were measured in human lumbar cerebrospinal fluid. All samples were preconcentrated by extraction with ethyl acetate. Deconjugation of the sulfate form of MHPG was achieved by enzymatic hydrolysis with sulfatase. Peaks were identified on the basis of chromatographic behavior, ratio of responses at several oxidation potentials and the stopped-flow UV spectra of the collected fractions. The free MHPG content of 20 cerebrospinal fluid samples ranged between 0.720 and 19.51 ng/ml with the mean of 5.126 +/- 4.652 (S.D.) ng/ml. The sulfate conjugate of MHPG in 12 samples of cerebrospinal fluid ranged between 0.08 and 0.850 ng/ml with the mean value of 0.2365 +/- 0.2269 (S.D.) ng/ml. Although our results correlate well with the literature values, no attempt was made to interpret the quantitative data since samples were obtained from routine, diagnostic testing of patients admitted to the medical or neurologic services at the Mount Sinai Hospital.

Benign pheochromocytoma associated with elevated excretion of homovanillic acid

The excretion of catecholamine metabolites was determined in nine children prior to and following resection of one or more well-encapsulated, benign pheochromocytomas. One third of these subjects presented with increased excretion of homovanillic acid as well as markedly increased excretion of vanillylmandelic acid and total metanephrines: biochemical evidence opposed to the presence of a benign pheochromocytoma. No significant difference in age, sex, clinical presentation, course, or postoperative biochemical evaluation could be detected between this group and the six remaining subjects. Elevated homovanillic acid excretion, indicative of the presence of a malignant pheochromocytoma in the adult, does not carry this serious prognostic import in childhood. In childhood, elevated homovanillic acid and markedly increased excration of vanillylmandelic acid and total metanephrines, usually associated with neuroblastoma, do not rule out the diagnostic possibility of a benign pheochromocytoma.

Plasma epinephrine concentration in healthy men: correlation with systolic pressure and rate-pressure product

Relations among plasma epinephrine, norepinephrine and renin activity and systolic pressure, diastolic pressure, heart rate and the product of heart rate and systolic pressure (rate-pressure product) were evaluated in 31 healthy men whose arterial pressure spanned the range from normal to mildly elevated. Measurements were made during 60 minutes with the patient in the supine position and during 10 minutes of quiet standing. In the supine position, highly significant regressions were found between systolic pressure or rate-pressure product and plasma epinephrine, but not between these variables and norepinephrine or renin activity. A weakly significant correlation was also found between heart rate and norepinephrine. On standing, norepinephrine and epinephrine increased significantly. In this position, rate-pressure product was significantly related by regression analysis only with plasma epinephrine. Weakly significant correlations between systolic pressure and epinephrine and between heart rate and norepinephrine and epinephrine were also found. Plasma renin activity was not significantly correlated with arterial pressure, heart rate or rate-pressure product in either position. These results suggest that plasma epinephrine is a determinant of systolic pressure when postural reflexes are minimized and that epinephrine may participate in control of cardiac work load, as reflected by rate-pressure product in the absence of exercise or definable stress.

Effect of guanabenz on blood pressure responses to posture and exercise

A single dose of guanabenz was examined for effects upon blood pressure, heart rate, plasma catecholamines, and plasma renin activity in a randomized, double‐blind, crossover design. Eight patients were studied when supine, standing, and during submaximal exercise. Guanabenz reduced blood pressure in subjects who were supine or standing. Heart rate was lowered only in the supine subjects. Guanabenz induced reduction in plasma catecholamines subjects in all positions and the reduction correlated with the placebo level for both norepinephrine and epinephrine. Plasma renin activity was not significantly affected by guanabenz. The results indicate that the central alpha‐agonist action of guanabenz reduces sympathoadrenal function to a greater extent in hyperadrenergic hypertensive patients than in those without this disorder.

Determination of nanogram amounts of catecholamine metabolites in amniotic fluid

Abstract Amniotic fluid samples obtained from 15–25 weeks of gestation were analyzed for catecholamine metabolites. The average levels obtained were 4.26 ng/ml for normetanephrine, 58.4 pg/ml for norepinephrine, 187.8 pg/ml for epinephrine and 975.4 pg/ml for dopamine. Gas liquid chromatographic assays for free and total 3-methoxy-4-hydroxyphenylethylene glycol gave the following values, respectively 3.93 ng/ml and 5.54 ng/ml.

Metabolism of D, L-3H-Norepinephrine in Essential Hypertension

Defective control of the cardiovascular system by the sympathetic nerves continues to be incriminated as the potential primary physiologic defect in essential hypertension (EH). The need to measure sympathetic tone has progressed from physiologic mensuration by assessment of reflex and pharmacological responses to the recent assay of norepinephrine (NE) and its congeners in both urine and plasma. The way in which the body handles D,L-B-3H-NE represents yet another technique by which to evaluate sympathetic function. Previous studies of EH by this method demonstrated more rapid plasma disappearance of 3H-NE as well as elevated 24 hour tritium accumulation in the urine following D,L-B-3H-NE injection. The present study of 7 normotensive subjects and 7 patients with EH was designed to depict more precisely these abnormalities in 3H-NE-metabolism. Following a one minute injection of 8 micrograms D,L-B-3H-NE, (200 microCi) intravenously, the excretion of unlabeled endogenous metabolites and their labeled congeners was assayed. By these means one could estimate catecholamine synthesis, turnover of the labeled pools, and by comparison of relative specific activities of the metabolites, gain some insight into the distribution of the injected material. Alternative catabolic pathways were evaluated by measurement of the excretion of 3H2O. Patients with EH excreted more label per 24 hours, revealed a more rapid decline of 3H2O excretion and lower specific activity of normetanephrine (NM). These findings are compatible with changes in pool dynamics and distribution of administered label which gave additional support to the concept of adrenergic dysfunction in association with essential hypertension.