Simultaneous determination of free catecholamines and epinine and estimation of total epinine and dopamine in plasma and urine by high-performance liquid chromatography with fluorimetric detection

Epinine (N-methyldopamine) is the pharmacologically active hydrolysis product of the prodrug ibopamine, which is currently being widely studied for the treatment of congestive heart failure. This paper reports a sensitive and reliable method for the simultaneous determination of free catecholamines and epinine in plasma and urine. The compounds are isolated from plasma or urine by a specific liquid-liquid extraction, derivatized with the selective fluorogenic agent 1,2-diphenylethylenediamine, and quantitated by high-performance liquid chromatography with gradient elution and fluorimetric detection. The limits of detection for the derivatized catecholamines and epinine are 0.3-0.6 pg of injected compound. Intra- and inter-assay coefficients of variation of all four compounds are good (1-8%), as are the accuracy and linearity. A method is also reported for the determination of total dopamine and epinine in plasma and urine based on the same principle. This method, in which deconjugation is accomplished by acid hydrolysis at 95 degrees C, also shows good sensitivity and reproducibility.

Renal insufficiency due to bilateral primary renal lymphoma

Diffusely enlarged nonhydronephrotic kidneys on ultrasound and computer-tomographic examination in a case of progressive preterminal renal insufficiency were very suggestive of extensive lymphomatous infiltration. Diffuse infiltration of the kidney by centrocytic/centroblastic non-Hodgkin lymphoma was confirmed upon renal biopsy. No other localizations of lymphoma could be found. After four courses of CHOP chemotherapy there was a complete remission of this primary renal non-Hodgkin lymphoma, with complete recovery of renal function.

Second Björn Folkow Award Lecture. The renin-angiotensin system: new surprises ahead

There is considerable evidence that the vascular renin-angiotensin systems contribute to the structural adaptations of hypertension. This article describes recent clinical data on local angiotensin formation in different vascular beds together with clinical findings that support the possible involvement of prorenin, in addition to renin, in local angiotensin formation. Our measurements of steady-state arterial and venous plasma levels of systemically infused 125I-angiotensin (Ang) I and of endogenous Ang I across a number of vascular beds in untreated and captopril-treated hypertensive subjects have revealed that most of the Ang I production in the forearm, leg, and kidney appears to take place at tissue sites and not in circulating plasma. This local production depends mainly on plasma-derived renin of renal origin, however. When we also measured the levels of systemically infused 251I-Ang II across these vascular beds, we found that although a substantial fraction of Ang II in the regional veins was derived from new production and not from arterial delivery, most could be attributed to the conversion of arterially delivered Ang I. The exception was in the kidney, where about 70% of venous Ang II appeared to have been derived from Ang I produced in renal tissue. Thus, our results indicate that extrarenally synthesized renin does not contribute significantly to circulating levels of Ang I and II. The proposal that prorenin contributes to local extrarenal angiotensin formation is based on evidence that prorenin production occurs in a variety of tissues other than the kidney. This extrarenal production may lead to high levels of circulating prorenin, as seen in many diabetic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal failure and cholesterol crystal embolization: a report of 4 surviving cases and a review of the literature

Four patients with end-stage renal failure (suspected to be) caused by cholesterol crystal emboli are described. Although cholesterol crystal embolization is generally considered to be fatal specifically when it is associated with renal failure, all four patients survived and in three renal function improved after periods of 3 weeks to 14 months of hemo- or peritoneal dialysis. The literature on cholesterol crystal embolization is reviewed and possible mechanisms of (partial) recovery of renal function are discussed.

A neonate with idiopathic hyperaldosteronism

A boy with functional abnormalities of the gastro-intestinal tract, hyponatraemia, hypokalaemia and hypertension is described. All symptoms developed within the first 2 months of life. Increased aldosterone levels were associated with suppressed values in the renin-angiotensin system. The diagnosis of idiopathic hyperaldosteronism was made because of adrenal hyperplasia and the failure to suppress aldosterone to undetectable levels with glucocorticoids. Treatment with spironolactone alone, or in combination with either intravenous dopamine or ibopamine orally, amiloride, enalapril, hydralazine or clonidine corrected serum potassium values but failed to normalize blood pressure and to correct plasma renin activity and plasma aldosterone. However, the combination of spironolactone with nifedipine decreased blood pressure. Abnormal gastro-intestinal motility was corrected by low doses of oral magnesium hydroxide. To assess intracellular calcium homeostasis, the patient's peripheral blood mononuclear cells were incubated with increasing concentrations of calcium. As these cells failed to maintain physiological calcium concentration, a defect in intracellular calcium homeostasis was suspected.

Not norepinephrine but its oxidation products bind specifically to plasma proteins

Specific binding (up to 50%) of catecholamines to the plasma proteins albumin, transthyretin and alpha-1 acid glycoprotein has been reported repeatedly, but data are conflicting. In binding studies of tritiated norepinephrine (NE) to human serum albumin, we found specific binding to be an artifact, due to the presence of one or more oxidation products of NE which are rapidly formed at pH greater than 6.5. In the presence of large amounts of antioxidants NE is stable, and no specific binding occurs. The decrease in binding of tritiated NE with increasing amounts of nontritiated NE, previously thought to represent displacement, is actually the result of the inherent greater stability of NE at higher concentrations. A similar decrease in binding, this time representing real displacement, was obtained with increasing amounts of oxidation products, obtained by treating NE first with sodium hydroxide. Results with transthyretin, alpha-1 acid glycoprotein and with plasma were in full agreement with these conclusions. These observations emphasize the necessity for careful investigation of the purity and stability of the labeled ligand, not only in binding assays with catecholamines, but in binding assays in general. Our findings may also have bearings on the currently hotly pursued topic of catecholamine release in in vivo and in vitro experiments.

[A patient with a wide aorta and 2 wide kidney pelves: retroperitoneal fibrosis]

The case is discussed of a patient with renal insufficiency due to severe stenosis of both ureters brought about by a periaortic inflammatory process. Such periaortitis is seen in severe atherosclerosis; the condition allegedly occurs in 5 to 23% of all patients with an abdominal aortic aneurysm. The literature on this form of retroperitoneal fibrosis is reviewed.

Nonparallel effects of renin inhibitor treatment on plasma renin activity and angiotensins I and II in hypertensive subjects. An assay-related artifact

Nonparallel effects of renin inhibitor treatment on plasma renin activity (PRA) and the plasma levels of angiotensins (ANG), as well as on blood pressure, have been observed in subjects with hypertension. This study addresses the possibility that renin inhibitors may show a high degree of plasma protein binding in vivo and that displacement of protein-bound inhibitor during the assay of PRA in vitro may lead to overestimation of renin inhibition. Indeed, with the ultrafiltration technique it was found that 96% of the novel renin inhibitor Ro 42-5892, when added to EDTA plasma, was bound to protein. The angiotensinase inhibitors phenylmethylsulfonyl fluoride (PMSF) and 8-hydroxy-quinoline sulfate (8-OHQ), which are currently used in PRA assays, caused a displacement of protein-bound inhibitor, thereby increasing its free concentration. This displacement was sufficient to explain the reduction in IC 50 of Ro 42-5892, which was seen in the PRA assay when PMSF and 8-OHQ were added to plasma. Such reductions in IC 50 were also seen with the renin inhibitors CGP 29-287, CGP 38-560A, and SR 43-845. When Ro 42-5892 was given, 1 mg/kg intravenously in 10 min, to subjects with hypertension, it appeared that plasma ANG I and II returned to baseline after 6-8 h, whereas PRA measured in the presence of PMSF and 8-OHQ was still suppressed. However, when PRA was measured without these angiotensinase inhibitors, the inhibition of PRA was parallel to the suppression of ANG I and II.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal hemodynamics and the renin-angiotensin-aldosterone system in normotensive subjects with hypertensive and normotensive parents

BACKGROUND AND METHODS

The kidney is important in blood-pressure regulation, but its role in the development of essential hypertension is still subject to debate. We compared renal hemodynamics, measured in terms of the clearance of para-aminohippuric acid and inulin, and the characteristics of the renin-angiotensin-aldosterone system in three groups of normotensive subjects at different degrees of risk for hypertension: 41 subjects with two normotensive parents, 52 with one normotensive and one hypertensive parent, and 61 with two hypertensive parents. The subjects ranged in age from 7 to 32 years.

RESULTS

The mean renal blood flow was lower in the subjects with two hypertensive parents than in those with two normotensive parents (mean difference [+/- SE], 198 +/- 61 ml per minute per 1.73 m2 of body-surface area; P = 0.002). Moreover, both the filtration fraction and renal vascular resistance were higher in the subjects with two hypertensive parents (filtration fraction: mean difference, 3.0 +/- 1.1 percentage points; P = 0.006; renal vascular resistance: mean difference, 2.7 +/- 0.8 mm Hg per deciliter per minute per 1.73 m2; P = 0.006). The subjects with two hypertensive parents had lower plasma concentrations of renin (mean difference, 3.3 +/- 1.6 mU per liter; P = 0.03) and aldosterone (mean difference, 111 +/- 36 pmol per liter; P = 0.003) than those with two normotensive parents. The differences could not be explained by the small differences in blood pressure between the groups. The values in the subjects with one hypertensive and one normotensive parent fell between those for the other two groups.

CONCLUSIONS

Renal vasoconstriction is increased and renin and aldosterone secretion is decreased in young persons at risk for hypertension. These findings support the hypothesis that alterations in renal hemodynamics occur at an early stage in the development of familial hypertension.

Improved measurement of urinary catecholamines by liquid-liquid extraction, derivatization and high-performance liquid chromatography with fluorimetric detection

We report a sensitive and reliable assay for the determination of the urinary catecholamines norepinephrine, epinephrine and dopamine, based on selective extraction by a liquid-liquid extraction procedure, followed by selective derivatization with the fluorigenic agent 1,2-diphenylethylenediamine and quantification by high-performance liquid chromatography with fluorimetric detection. Comparison with a method using electrochemical detection shows that interference of an unknown compound, most probably N-methylepinephrine, which is an often-overlooked problem with methods using electrochemical detection and results in falsely high epinephrine concentrations, does not occur with the described fluorimetric method.

Plasma immunoreactive endothelin-1 in pregnant women with and without pre-eclampsia

In normotensive nonpregnant women (n = 23), the plasma concentrations of immunoreactive endothelin-1 (ir-ET-1) were not different from nonpregnant women with essential hypertension (n = 15): 3.6 (2.0-5.4) ng/L (mean, range) versus 3.8 (2.4-5.8) ng/L. In normotensive pregnant women (n = 25), the plasma level of ir-ET-1 was 2.1 (1.3-3.4) ng/L (p less than 0.01) lower than in normotensive nonpregnant women. Pre-eclamptic patients (n = 25) had elevated ir-ET-1 plasma levels of 5.0 (2.1-12.4) ng/L (p less than 0.001 for normotensive pregnant women, p less than 0.01 for nonpregnant women). The low level of ir-ET-1 in normotensive pregnant women may be explained by the increase in the distribution volume of ir-ET-1 during the course of pregnancy. Damage of vascular endothelium is a consistent morphological abnormality in pre-eclampsia. Elevated ir-ET-1 in plasma might be a biochemical marker of this abnormality and may contribute to the pathogenesis of pre-eclampsia.

First passage radionuclide cardiography for determination of cardiac output: a critical analysis

First-pass radiocardiography, by single probe or gamma camera, has the theoretic potential to be an attractive non-invasive indicator dilution method of measuring cardiac output. Registrations, once programmed, require little time to perform and entail hardly any risk for the subject. At the same time, they are to varying degrees inaccurate. As long as technology is not standardized, each institution that wishes to employ these measurements has to do its own critical validation before results can be accepted. As with any other indicator dilution technique, precision of radiocardiography is served by repetitive measurements. However, radiation dose and disturbing background radioactivity preclude taking multiple measurements within a short period. This holds particularly for the gamma camera. The speed and simplicity of the probe system make this device very suitable for serial evaluation of cardiac function at the bedside. Depending on collimation of the probe and extracardiac background activity, a correction factor has to be derived empirically to avoid overestimation of cardiac output. The major advantage of the gamma camera linked to a data system is that an infinite number of first-pass curves can be obtained from different parts of the heart. Provided that appropriate regions of interest are selected, first-pass studies can yield reasonably accurate and reproducible determinations of cardiac output. In addition, functional image analysis during the equilibrium phase enables calculation of other cardiac variables such as ejection fraction and chamber size. Nevertheless, standardization of 'hardware' and 'software' is imperative.

Increase in plasma prorenin during the menstrual cycle of a bilaterally nephrectomized woman

To investigate the origin of the prorenin peak that occurs during the normal menstrual cycle, plasma levels of prorenin, renin, oestradiol, progesterone, LH and FSH were measured serially in a nephrectomized woman having regular haemodialysis. The prorenin peak coincided with the LH surge and preceded the rise of progesterone, whereas renin was below the detection limit during the whole cycle. These findings indicate that the rise in prorenin during the menstrual cycle is not of renal origin but is probably due to increased production by the ovary and supports the increasing evidence for the existence of a local renin-angiotensin system in the ovary.

Intrarenal de novo production of angiotensin I in subjects with renal artery stenosis

To estimate the renal extraction and de novo production of angiotensin I and to assess the contribution of blood-borne renin to renal angiotensin I production, the aortic and renal venous plasma levels of renin and intact [125I]angiotensin I and endogenous angiotensin I during continuous systemic intravenous infusion of monoiodinated [125I]angiotensin I were measured in subjects with unilateral renal artery stenosis (n = 8) who were treated with captopril (50 mg b.i.d.). Results demonstrated that 80% of angiotensin I delivered by the renal artery was extracted both by the affected and the unaffected kidney and that on both sides a major part of angiotensin I in the renal vein was derived from intrarenal de novo production. Production of plasma angiotensin I was in excess over extraction (p less than 0.01) on the affected side, whereas extraction was in excess over production (p less than 0.01) on the contralateral side. The plasma level of de novo intrarenally produced angiotensin I in the renal vein was seven times higher on the affected side than the contralateral side. This difference was by far too big to be explained by a difference in the transit time of blood between the two kidneys, by an augmented production of angiotensin I in the circulating blood passing through the affected kidney due to the higher level of venous plasma renin activity in that kidney, or by the combination of both.(ABSTRACT TRUNCATED AT 250 WORDS)

High plasma prorenin in diabetes mellitus and its correlation with some complications

Plasma prorenin is abnormally high, whereas renin is normal or even low, in many patients with long-standing diabetes mellitus complicated by microvascular disease. Nephropathy or autonomic neuropathy has been put forward as a cause. We found that in 223 consecutive diabetics prorenin correlated positively with serum creatinine, the presence of macroalbuminuria (greater than 250 mg/L), and the presence of diabetic retinopathy, particularly the proliferative type. This correlation did not depend on the presence of neuropathy or whether the patient was receiving insulin. It was also independent of sex, age, duration of diabetes, blood pressure, and blood levels of glucose and hemoglobin-A1c. The association between elevated prorenin and retinopathy remained significant after adjustment for creatinine and the presence of macroalbuminuria. Of the whole group of diabetics 94 consecutive patients were assessed for the presence of microalbuminuria (30-300 mg/24 h). Independently of the presence of micro- or macroalbuminuria, the mean level of prorenin was not above normal in the patients without retinopathy and was 2-3 times normal in those with proliferative retinopathy. Thus, retinopathy appears to be a more important determinant of abnormally high prorenin than nephropathy. In addition, the renal vein to artery ratio of prorenin in 7 diabetics with both advanced nephropathy and proliferative retinopathy was not elevated, despite the high peripheral venous prorenin level and the impaired renal perfusion. Thus, the abnormally high prorenin level in these patients could not be explained by abnormal secretion by the kidneys. Finally, prorenin was not high in 16 nondiabetics with loss of sympathetic activity due to chronic autonomic neuropathy, which indicates that in the absence of diabetes, this type of autonomic failure is not sufficient to cause the high prorenin levels seen in diabetics. Our findings are evidence that abnormally high plasma prorenin levels in diabetics are not an immediate consequence of altered glucose metabolism. This abnormality is related to the development of microvascular disease in the eye and kidney and is at least in part due to decreased clearance of prorenin from the circulation, increased production from extrarenal sources, or both.

Prolonged blood pressure reduction by orally active renin inhibitor RO 42-5892 in essential hypertension

OBJECTIVE

To investigate the effects of a novel specific renin inhibitor, RO 42-5892, with high affinity for human renin (Ki = 0.5 x 10(-9) mol/l), on plasma renin activity and angiotensin II concentration and on 24 hour ambulatory blood pressure in essential hypertension.

DESIGN

Exploratory study in which active treatment was preceded by placebo.

SETTING

Inpatient unit of teaching hospital.

PATIENTS

Nine men with uncomplicated essential hypertension who had a normal sodium intake.

INTERVENTIONS

Two single intravenous doses of RO 42-5892 (100 and 1,000 micrograms/kg in 10 minutes) given to six patients and one single oral dose (600 mg) given to the three others as well as to three of the patients who also received the two intravenous doses.

RESULTS

With both intravenous and oral doses renin activity fell in 10 minutes to undetectably low values, while angiotensin II concentration fell overall by 80-90% with intravenous dosing and by 30-40% after the oral dose. Angiotensin II concentration was back to baseline four hours after the low and six hours after the high intravenous dose and remained low for at least eight hours after the oral dose. Blood pressure fell rapidly both after low and high intravenous doses and after the oral dose and remained low for hours. With the high intravenous dose the daytime (0900-2230), night time (2300-0600), and next morning (0630-0830) systolic blood pressures were significantly (p less than 0.05) lowered by 12.5 (95% confidence interval 5.6 to 19.7), 12.2 (5.4 to 19.3), and 10.7 (3.2 to 18.5) mm Hg respectively, and daytime diastolic pressure was lowered by 9.3 (2.2 to 16.8) mmHg. With the oral dose daytime, night time, and next morning systolic blood pressures were lowered by 10.3 (5.5 to 15.4), 10.5 (4.2 to 17.2), and 9.7 (4.0 to 15.6) mm Hg, and daytime and night time diastolic pressures were lowered by 5.8 (0.9 to 11.0) and 6.0 (0.3-12) mm Hg respectively.

CONCLUSIONS

The effect of the inhibitor on blood pressure was maintained over a longer period than its effect on angiotensin II. RO 42-5892 is orally active and has a prolonged antihypertensive effect in patients who did not have sodium depletion. This prolonged effect seems to be independent, at least in part, of the suppression of circulating angiotensin II.

Acute effects and mechanism of action of ketanserin in patients with primary Raynaud's phenomenon

This study evaluates the vasoactive effects and mode of action of ketanserin, a selective 5HT2 receptor antagonist, on digital circulation in 11 patients with primary Raynaud's phenomenon. Reflex digital vasoconstriction was induced by moderate body cooling. We found that ketanserin given intravenously in a dose of 10 mg, normalized digital skin temperature and digital blood flow as estimated by venous occlusion plethysmography and laser-Doppler flowmetry. However, effects of ketanserin on transcutaneously measured oxygen pressure were modest. This could imply a preferential effect of ketanserin on arteriovenous shunt flow. Pretreatment with high doses of the selective and nonselective alpha-adrenoreceptor antagonists prazosin and phentolamine did not abolish the effects of ketanserin on digital blood flow. However, under alpha-adrenoceptor blockade the small effects of ketanserin on normal blood pressure disappeared. Thus, in contrast to the effects in the systemic circulation, the principal mechanism underlying digital vasodilation after ketanserin is unlikely to involve alpha-adrenoceptor antagonism. We conclude that 5HT2 receptors are present in the digital vasculature. In patients with primary Raynaud's phenomenon, their activation plays an important role in cold-induced digital vasoconstriction.

Epinephrine-induced enhancement of sympathetic activity in humans: inhibition by nonselective as well as beta 1-selective beta-adrenoceptor blockade

To collect further evidence that epinephrine (EPI) facilitates norepinephrine (NE) release in humans, the effect of a low-dose intravenous (i.v.) infusion of EPI (20 ng kg-1/min) on arterial levels of NE and on local production of NE in the forearm was studied both before and during isometric exercise, cold provocation, head-up tilting, and mental stress in 10 subjects with borderline to mild hypertension. Studies were performed during placebo, during beta 1-selective beta-adrenoceptor blockade with atenolol, 50 mg once daily, and during nonselective beta-blockade with bopindolol, 1 mg once daily. Atenolol and bopindolol were administered for 1 week, 2 weeks apart, in a randomized double-blind cross-over design. During infusion of EPI, which increased plasma EPI levels to within the high physiologic range, resting levels of NE increased from 214 +/- 20 to 263 +/- 26 pg/ml (p less than 0.01) and resting NE forearm production increased from 296 +/- 48 to 529 +/- 98 pg 100 ml/min-1 (p less than 0.01). The enhancement of these two indices of sympathetic activity by EPI, observed during placebo, was abolished by bopindolol as well as by atenolol. The response of arterial NE, but not the response of forearm NE production, to three of the four stress tests was also enhanced (p less than 0.05) by EPI. This enhancement was also abolished by both beta-adrenoceptor antagonists. Our findings support the hypothesis that physiologic levels of EPI are capable of enhancing sympathetic activity in humans. This effect is mediated by beta-adrenoceptors and can be blocked not only by a nonselective but also by a beta 1-selective beta-adrenoceptor antagonist.

Identification and quantification of renin and prorenin in the bovine eye

Angiotensin-II, the most important biologically active product of the renin-angiotensin system, has been reported to play a role in neovascularization, and prorenin has been found in the vitreous of human eyes, particularly in those affected by proliferative diabetic retinopathy, a disease characterized by neovascularization. The prorenin level in these eyes was, relative to that of plasma albumin, higher than in eyes without neovascularization. These findings suggested that an intraocular renin-angiotensin system exists, which might be involved in the development of retinal neovascularization in diabetes mellitus. In this study angiotensin-I-generating activity was measured in bovine aqueous humor and vitreous and in extracts of bovine retina, pigment epithelium-choroid, and anterior uveal tract before and after subjecting these extracts to procedures known to convert prorenin to renin. The measurements were made by incubation at 37 C with plasma from nephrectomized rats at pH ranging from 5.0-8.5. True renin in the ocular samples could be separated from nonrenin acid protease by alpha-casein-Sepharose affinity column chromatography at pH 3.5; true renin did not bind to the column, whereas acid protease did. True renin was further identified by its relatively high pH optimum (6.5-7.0) for angiotensin-I generation, its complete inhibition with specific renin antiserum, and its high affinity for specific renin inhibitors. More than 75% of angiotensin-I-generating activity of the ocular samples consisted of true renin. Approximately 90% or more of total renin (renin plus prorenin) in aqueous humor, vitreous, and ocular tissue could not be explained by trapped plasma. Total renin in aqueous humor and renin in vitreous were near the detection limit of the assay of angiotensin-I-generating activity. In vitreous prorenin comprised 99% of the total renin, in retina 81%, and in pigment epithelium-choroid and anterior uveal tract less than 50%. Prorenin in ocular fluids showed a concentration gradient, posterior vitreous greater than anterior vitreous greater than aqueous humor, suggesting that the main source of extracellular prorenin was in the posterior eye. These data support the contention of local renin and/or prorenin synthesis in the eye and are in accordance with the observations in other tissues that extrarenal synthesis of renin is often associated with the release of mainly, or exclusively, prorenin into extracellular fluid.

Normal homeostasis of fibrinolysis in nephrogenic diabetes insipidus in spite of defective V2- receptor-mediated responses of tissue plasminogen activator release

Three patients with congenital, nephrogenic diabetes insipidus (NDI) from two unrelated families were tested for haemostatic and fibrinolytic responses to DDAVP infusion and venous occlusion. None of the three patients showed a response of factor VIII:C, vWF:Ag or t-PA to DDAVP, a V2-agonist. However, the baseline levels of these factors in the patients' plasma were normal and during venous occlusion a rise in t-PA antigen and t-PA activity was observed in all patients. One patient showed a definite response of the t-PA antigen level to exercise. It is concluded that (extrarenal) V2-receptor-mediated responses are absent in these patients, but that baseline homeostasis and the response to venous occlusion and physical exertion are intact. Presumably, these depend on other mechanisms. This observation denies a central role for vasopressin receptors in the on-demand regulation of clotting and clot dissolving properties of the blood.