Aldosterone in primary hypertension relationship to plasma renin activity and urinary electrolytes and a comparison with normotensive subjects

Transiently Elevated TC and sdLDL-C Levels and Falsely Low LDL-C Levels in Patients with Extrahepatic Cholangiocarcinoma

Purpose

Most patients diagnosed with extrahepatic cholangiocarcinoma (ECCA) exhibit cholestasis caused by obstruction of the bile duct. Cholestasis is associated with lipid disorders, but studies focused on the changing lipid parameters in patients with ECCA are lacking. Here, we observed lipid profiles in patients with ECCA and investigated whether the removal of biliary obstruction could correct dyslipidemia.

Patients and Methods

We consecutively included patients admitted to the hepatobiliary surgery department at the Affiliated Hospital of Xuzhou Medical University. The patients were divided into an ECCA group or a non-ECCA group based on the disease assessment. Patients with histological confirmation of ECCA were included in the ECCA group. Blood samples were collected on admission as well as five days after treatment. An automatic biochemistry analyzer was used to test liver function and serum lipid levels. Serum lipoprotein electrophoresis was performed using barbitone sodium buffer and Sudan black B.

Results

A total of 180 patients met inclusion criteria and were enrolled for this study. Of these, 76 patients were diagnosed with ECCA; all other patients were enrolled in the non-ECCA group. Total cholesterol (TC) and small and dense low-density lipoprotein cholesterol (sdLDL-C) levels were significantly elevated in the ECCA group. LDL-C levels were found to be slightly lower in the ECCA group. In the ECCA group, serum samples were detained in sample wells and lipoproteins failed to be separated. TC and sdLDL-C levels significantly decreased after cholestasis relief in the ECCA group. Lipoprotein electrophoresis revealed that patients with ECCA showed normal lipoprotein patterns after treatment.

Conclusion

Patients with ECCA exhibited transiently elevated TC and sdLDL-C levels and falsely low LDL-C results. TC, sdLDL-C, and LDL-C levels could be restored to normal levels after biliary obstruction removal and cholestasis relief.

History of hepatic bile formation: old problems, new approaches

Studies of hepatic bile formation reported in 1958 established that it was an osmotically generated water flow. Intravenous infusion of sodium taurocholate established a high correlation between hepatic bile flow and bile acid excretion. Secretin, a hormone that stimulates bicarbonate secretion, was also found to increase hepatic bile flow. The sources of the water entering the biliary system with these two stimuli were differentiated by the use of mannitol. An increase in its excretion parallels the increase in bile flow in response to bile acids but not secretin, which led to a quantitative distinction between canalicular and ductular water flow. The finding of aquaglyceroporin-9 in the basolateral surface of the hepatocyte accounted for the rapid entry of mannitol into hepatocytes and its exclusion from water movement in the ductules where aquaporin-1 is present. Electron microscopy demonstrated that bile acids generate the formation of vesicles that contain lecithin and cholesterol after their receptor-mediated canalicular transport. Biophysical studies established that the osmotic effect of bile acids varies with their concentration and also with the proportion of mono-, di-, and trihydroxy bile acids and provides a basis for understanding their physiological effects. Because of the varying osmotic effect of bile acids, it is difficult to quantify bile acid independent flow generated by other solutes, such as glutathione, which enters the biliary system. Monohydroxy bile acids, by markedly increasing aggregation number, severely reduce water flow. Developing biomarkers for the noninvasive assessment of normal hepatic bile flow remains an elusive goal that merits further study.

Blood pressure in relation to the renin-angiotensin-aldosterone system

The relationship between blood pressure (BP) and the renin-angiotensin-aldosterone system was studied in a stratified random sample (n=120) of 49-year-old men selected from a BP screening and covering a wide range of BPs. Only subjects not on antihypertensive treatment were included. None had malignant or secondary hypertension. Plasma renin activity, plasma concentrations of angiotensin II, aldosterone, sodium, potassium and noradrenaline and the 24-hour urinary excretions of sodium, cortisol and noradrenaline were determined. Of these variables, only p-aldosterone was significantly correlated wtih BP, both in the whole study group (R=0.22, p less than 0.02, n=119) and in the subjects with the highest BP range (R=0.36, p less than 0.02, n=30). Of the clinical groups compared, the hypertensive subjects had significantly higher mean p-aldosterone than the borderline and normotensive subjects. Multiple regression analysis showed that the 24-hour urinary excretion of noradrenaline was the factor most strongly correlated to p-aldosterone, suggesting that the sympathetic nervous system might stimulate aldosterone secretion. Our findings indicate that aldosterone may be of importance for the development and maintenance of essential hypertension.

Angiotensin II in primary hypertension, relationship to plasma renin activity, aldosterone and urinary electrolytes

Plasma concentrations of angiotensin II (AII) were studied in 36 patients with primary (essential) hypertension and 15 normotensive control subjects during basal (1 h supine rest), upright and frusemide-stimulated (80 mg orally) conditions. Plasma renin activity (PRA) and plasma aldosterone (PA) were determined on the same occasions. AII was then correlated statistically to PRA, PA and 24-hour urinary excretions of aldosterone (Aldo-U), sodium and potassium and to the blood pressure (BP) levels. The AII values in the hypertensive patients were not statistically significantly different from those in the normotensive subjects. A close relationship was found between the AII values and the corresponding PRA values in the hypertensive patients (r=0.65--0.76, p less than 0.001 for all). Correlations between AII and PA, and AII and Aldo-U were not consistently significant. No correlation was found between AII and BP or between AII and 24-hour urinary electrolytes. The findings point to an intact function between PRA and AII but a disturbed AII-aldosterone interrelation in primary hypertension.

Influence of mild sodium depletion upon peripheral and centrally mediated effects of intravenous angiotensin II in the goat

Previous evidence for cerebral sodium/angiotensin interaction concerning centrally mediated effects of angiotensin II (AII) provided the incitement to compare in goats effects of i.v. AII during sodium repletion (SR) with those obtained during mild sodium depletion (SD). The experiments were performed in the euhydrated as well as hyperhydrated animals, and AII was infused for 10 min at 40 pmol kg-1 min-1. It was confirmed that SD is associated with elevated plasma aldosterone concentration (PA) and (as regards aldosterone secretion) a sensitization of the adrenal cortex. In contrast to PA, the plasma cortisol (PC) response to i.v. AII was significantly reduced during SD, apparently due to diminished cerebral sensitivity to circulating AII. A similar SD-associated attenuation was observed during euhydration as regards release of arginine vasopressin (AVP) in response to i.v. AII, and during hyperhydration as regards the antidiuretic effect of the octapeptide. It was confirmed that the pressor effect of i.v. AII becomes markedly reduced during SD. However, in spite of this, the associated bradycardia remained the same during SR and SD, suggesting that SD also attenuated the centrally mediated chronotropic effect of AII.

Aldosterone secretion during acute metabolic and respiratory alkalosis in the goat

Metabolic and respiratory alkalosis were produced in goats with the primary aim of studying possible influence of a reduced blood hydrogen ion concentration on aldosterone secretion. Metabolic alkalosis was induced by 1 h i.v. infusion of hypertonic tris(hydroxy-methyl)aminomethane (THAM) solution. The infusion was associated with a significant reduction in plasma aldosterone concentration (PA). It occurred in the absence of a detectable fall in plasma K or obvious change in plasma renin activity, but simultaneously with a moderate increase in plasma cortisol concentration and a significant reduction of plasma Na concentration. It suggests that changes of the primary aldosterone regulators were not the cause of the fall in PA, but leaves open the possibility that either the decreased blood hydrogen ion concentration as such or THAM-induced blood hypertonicity reduced the aldosterone secretion. The respiratory alkalosis was due to heat polypnoea elicited by 2 h exposure of the goats to 45 degrees C. Here, no obvious change in PA was observed during the alkalotic period, which, however, was associated with a rise in plasma K. Increased K stimulation may therefore have masked a possible inhibitory influence of the alkalosis upon the aldosterone secretion.

Aldosterone secretion during acute respiratory acidosis and NH4Cl-induced metabolic acidosis in the goat

Acute respiratory acidosis was induced in goats by inhalation of 6% or 8% CO2 in air for 30 min. The lower CO2 concentration caused a significant rise in plasma cortisol (PC), but had no appreciable influence upon plasma aldosterone (PA), and did not affect the arterial blood pressure (aBP). A more pronounced PC response was observed in association with the inhalation of 8% CO2, but also here without concomitant increase in PA. However, the aBP became elevated by about 30% during the CO2 exposure with a simultaneous increase in glomerular filtration rate and a water diuresis, suggesting that the release of arginine vasopressin temporarily became inhibited. It was confirmed that metabolic acidosis induced by duodenal NH4Cl administration is preceded by a transient rise in PA. Dexamethasone-induced feedback inhibition of the ACTH secretion blocked the PA response, which possibly reflects NH4 ion stimulation of the ACTH release. The combined results of the CO2 and NH4Cl experiments seem to justify the conclusion that increases in PA seen in conjunction with acidosis do not reflect a direct hydrogen ion stimulation of the adrenal glomerulosa cells.

Intracerebroventricular and systemic saralasin used to investigate angiotensin-elicited activation of the pituitary-adrenocortical axis in the goat

Intracerebroventricular (ICV) infusion of the competitive inhibitor for angiotensin II (AII), saralasin, (13 pmol kg-1 min-1), preceding and outlasting the intravenous (i.v.) infusion of AII (40 pmol kg-1 min-1) extinguished the elevation in plasma cortisol (PC) obtained in response to just the i.v. AII infusion. The corresponding i.v. infusion of saralasin did not visibly influence the AII-induced elevation of PC, whereas bilateral intracarotid infusions of the inhibitor tended to reduce the response. The ICV administration of the inhibitor also significantly reduced the rise in plasma aldosterone (PA) seen as an effect of the i.v. AII. Paradoxically, however, the intravascular infusions of saralasin conspicuously augmented the rise in PA obtained after the simultaneous i.v. infusion of AII. It is concluded that cerebral mediation of the ACTH-cortisol response to systemic AII occurs at sites accessible to inhibition from both sides of the blood-brain barrier, and that also the PA response to blood-borne AII may be to some extent cerebrally mediated.

Endotoxin-induced prostaglandin (PGF2 alpha) biosynthesis, fever and miosis in dexamethasone-treated goats

Prostaglandin-releasing, adrenocortical, febrile and miotic responses to endotoxin (ET) (E. coli lipopolysaccharide; 0.25 microgram kg-1) were studied in goats with and without prolonged dexamethasone influence. The i.v. injection of ET induced a three-fold peak elevation in plasma 15-ketodihydro-PGF2 alpha at 1.5 h post-injection, that is, between the first and second phase of the temperature elevation. During the latter phase, the plasma concentration of this primary PGF 2 alpha metabolite gradually returned to basal level, which implies that the second phase of ET fever is not PG dependent. The PG response exhibited a similar pattern, but was less pronounced in the dexamethasone-ET experiments, where the duration of maximum temperature elevation and of the miosis became shortened by about 20 min, and the typical biphasic pattern of ET fever was no longer seen. The ET-induced rise in plasma aldosterone concentration was completely blocked by dexamethasone. The corresponding rise in plasma cortisol concentration was prevented for 2 h, but was later only partially inhibited in spite of the repeated dexamethasone treatment.

Systemic and centrally mediated angiotensin II effects in the horse

The primary aim of the study was to evaluate the potential value of intravenous (i.v.) infusion of angiotensin II (AII) for phonocardiographic differential diagnosis of equine valvular insufficiency. Ten-minute AII infusions at 4.5-33 pmol kg-1 min-1 induced clear-cut dose-dependent rises in systemic arterial blood pressure (aBP), whereas the pulmonary aBP remained largely unaffected. It implies that i.v. infusion of AII at about 10 pmol kg-1 min-1 could be a valuable tool for the acoustic differentiation between mitral and tricuspid valvular dysfunction in the horse. The infusion at, and above 9 pmol kg-1 min-1 caused increased heart rate. This chronotrophic effect was not strictly dose-dependent and exhibited significant tachyphylaxis. Angiotensin II administration at, or above 9 pmol kg-1 min-1 was needed to induce an urge to drink, suggesting that angiotensin-induced thirst does not appear in the euhydrated horse until the octapeptide reaches supraphysiological blood concentration. Determinations of plasma aldosterone concentration (PA) revealed comparatively high morning control values (269 +/- 46 pmol-1). Three consecutive AII infusions with 10-min intervals and at increasing dosages caused a cumulative, almost fourfold elevation of PA. The PA pattern indicated that AII-induced hypersecretion of aldosterone continued for several minutes after the end of the infusions, but also showed that the metabolic clearance of the hormone took precedency of the secretion within 20 min post-infusion. In two of the horses a fall in PA occurred during a fourth, final infusion, indicating that in these instances the previous AII administration had impoverished the store of aldosterone available for release from the adrenal cortex.

Ammonium chloride induced acidosis and aldosterone secretion in the goat

Responses to 30-min intraduodenal infusion of NH4Cl (total amount 75 mmol) were studied in conscious goats. The infusion caused an immediate, transient rise in plasma aldosterone concentration (PA) from a mean of 78 to 221 pmo l-1. As expected, the NH4Cl administration also induced metabolic acidosis, initially subjected to partial respiratory compensation. The acidosis did not become fully developed until 1 h after cessation of the infusion, when PA had almost returned to its initial level. Renal compensation of the acidosis was shown by acidification of the urine and reduced Na excretion being most pronounced 1-2 h post-infusion. During the infusion blood haemoglobin concentration and the haematocrit increased by 25 and 13%, respectively, without simultaneous increase in plasma protein concentration and with persisting ear vasodilatation, indicating a mobilization of stored erythrocytes in the absence of a general increase in sympathetic tone. The results suggest that the reduction of blood pH is not the cause of the increase in PA occurring in association with NH4Cl-induced metabolic acidosis, but leave open the possibility that this increase may be due to some centrally mediated or direct adrenal influence of NH+4. As regards the apparent NH4Cl-induced mobilization of stored erythrocytes, it is suggested that such a response may play a role in the defence against acidosis by increasing the buffering capacity of the circulating blood.

Influence of heat exposure on acid/base and fluid balance in hyperhydrated goats

Hyperhydrated goats were exposed to an environmental temperature of 45 degrees C (relative humidity 70%) for 120 min. After 90 min, rectal temperature and respiratory frequency reached plateau levels of 40.5 degrees C and 280 respirations min-1, respectively. Measurements of arterial and venous blood acid-base parameters revealed that respiratory alkalosis had started to develop after 60 min, and had become obvious at the end of the heat exposure period. Renal compensation (evidenced by gradual increases in urinary pH and renal Na excretion) developed in parallel with the respiratory alkalosis. The heat exposure elicited a moderate, temporary inhibition of the water diuresis, but no obvious increase in the renal excretion of arginine vasopressin (antidiuretic hormone, ADH). Preliminary determinations of plasma aldosterone did not show any change during the actual heat exposure period, but a 50% temporary decrease in plasma aldosterone 30 min thereafter. The study confirms the susceptibility of goats to develop respiratory alkalosis during thermoregulatory panting, and shows that this is not to any appreciable extent diminished during hyperhydration. It can further be concluded that a heat-induced rise in body temperature to 40.5 degrees C is no powerful stimulus for vasopressin release in the hyperhydrated goat. The determinations of plasma aldosterone suggest that reduced liberation of the hormone does not contribute to the immediate renal compensation of respiratory alkalosis, but that respiratory alkalosis reaching a certain intensity inhibits aldosterone secretion.

Effects of hay-feeding on acid/base balance, renal sodium excretion, aldosterone and vasopressin secretion in the goat

Effects of 30 min intense hay-feeding on acid/base and sodium homeostasis were studied in semi-starved goats during hyper- and euhydration. Parallel analyses of carotid and jugular blood samples revealed that feeding induced metabolic acidosis, which to some extent was subjected to respiratory compensation. The acidosis was accompanied by renal sodium retention and urinary acidification persisting for 2-3 h. The sodium retention was succeeded by an increase in renal Na excretion above the initial level. This natriuresis was most accentuated during hyperhydration. Blood samples taken for hormone assays during euhydration revealed a 15% increase in haematocrit and a significant rise in plasma aldosterone at termination of feeding. Inhibition of the water diuresis in hyperhydrated animals, and moderate increases in renal arginine vasopressin (AVP) excretion and plasma AVP were inconsistent effects of feeding. It is concluded, that simply jugular vein blood provides reliable information on the acid/base status of goats, but that the feeding schedule has to be considered in all experiments where small ruminants are used to investigate the integrated control of acid/base and sodium homeostasis.

Interactions between digitonin and bilayer membranes

The morphology of interactions between digitonin and cholesterol has been investigated. When precipitated from ethanolic solutions, digitonin-cholesterol complexes form in flat lamellar sheets. In contrast, when the complex is formed in a bilayer membrane, the membrane is deformed into corrugations of hemitubules. The polarity of the deformations formed in bilayer membranes is highly correlated with the direction of entry of digitonin into the membrane. We suggest that the morphology of digitonin/cholesterol hemitubules is dependent upon the complex being formed within a bilayer and, in addition, is not correlated with asymmetry of cholesterol concentration across the membrane.

Disturbances in bile acid metabolism of infants with the Zellweger (cerebro-hepato-renal) syndrome

The bile acid pattern in bile and serum from two infants with the cerebro-hepato-renal syndrome of Zellweger was severely disturbed. An increased concentration particularly of trihydroxycoprostanic acid and also of dihydroxycoprostanic acid could be demonstrated. A generalized mitochondrial defect could explain these increased concentrations. This hypothesis is supported by the abnormal structure of the mitochondria in the liver biopsy of one of our patients. It is possible that the abnormal bile acids contribute to the liver damage of infants with Zellweger syndrome.

Inhibition of hepatic Na +, K + -adenosinetriphosphatase in taurolithocholate-induced cholestasis in the rat

Na +, K + -adenosinetriphosphatase (Na +, K + -ATPase) activity was decreased in liver plasma membranes from rats in which cholestasis had been induced by i.v. administration of sodium taurolithocholate (5 mumoles/100 g b. wt). Incubation of liver plasma membranes with taurolithocholate (10--1300 muM) caused significant and dose dependent reductions of Na +, K + -ATPase activity at taurolithocholate concentrations above 100 muM. These findings lend support to the hypothesis that cholestasis induced by monohydroxy bile acids is at least partially the result of an inhibition of hepatic Na +, K + -ATPase activity.