Effect of sodium chloride and sodium bicarbonate on blood pressure in stroke-prone spontaneously hypertensive rats.

1. To test the hypothesis that NaCl increases blood pressure, while NaHCO3 does not, we measured the effect of an NaHCO3-containing mineral water on blood pressure in stroke-prone spontaneously hypertensive (SHR-SP) and Wistar-Kyoto (WKY) rats. We compared mineral water with equimolar amounts of NaCl and demineralized drinking water in six groups of 20 rats each over 24 weeks. 2. NaCl consistently increased blood pressure in both SHR-SP and WKY compared with demineralized water, while mineral water did not. 3. We studied the possible role of sodium-regulating hormones. Sodium, potassium-dependent adenosine triphosphatase activity was decreased by NaCl and by age, but not by mineral water. The concentration of atrial natriuretic peptide was greater in SHR-SP, but was not influenced by the two regimens. Components of the renin-angiotensin-aldosterone system and 18-hydroxydeoxycorticosterone tended to decrease with NaCl, but not with mineral water. 4. Plasma pH values in the six groups of rats were not different; however, SHR-SP had consistently lower PCO2 and HCO3- values and higher anion gap values than WKY rats. These values were not influence by the two regimens. 5. NaCl elevates blood pressure in SHR-SP while NaHCO3 does not. The changes in hormones regulating sodium homoeostasis suggest that NaCl induces volume expansion while NaHCO3 does not. The effect may be related to influences on renal sodium reabsorption by chloride and bicarbonate. The possible role of increased proton excretory activity in SHR-SP remains to be determined.

Effect of high calcium diet on magnesium, catecholamines, and blood pressure of stroke-prone spontaneously hypertensive rats.

To test the effect of a high dietary calcium intake on blood pressure, we fed stroke-prone spontaneously hypertensive (SHR-SP) and Wistar-Kyoto rats (WKY) diets containing (a) 0.25% Ca/0.08% Mg, (b) 4.0% Ca/0.02% Mg, and (c) 4.0% Ca/0.08% mg, beginning at 6 weeks of age. SHR-SP and WKY rats receiving 4% Ca with the lower Mg content had lower blood pressures, hypomagnesemia, and hypomagnesuria, and grew poorly. SHR-SP receiving 4% Ca and the higher Mg diet had blood pressures no different from those of rats receiving the 0.25% Ca diet, in spite of having lower body weights. Rubidium flux studies in erythrocytes were not influenced by Ca or Mg in the diets. Plasma phosphate values were moderately reduced in rats receiving 4% Ca diets. Epinephrine and norepinephrine values were higher in SHR-SP than in WKY rats. Norepinephrine increased with stress in both strains, independent of diet. Epinephrine values were lower in SHR-SP receiving the 4% Ca diets and showed less of an increase with stress compared to SHR-SP receiving the 0.25% Ca diet. After 26 weeks of diets, SHR-SP and WKY rats were given 0.9% NaCl in their drinking water. NaCl increased blood pressure in SHR-SP irrespective of Ca content of the diet. These data suggest that a high Ca diet influences Mg homeostasis and adrenal medullary function in SHR-SP. Further, SHR-SP appear resistant to any blood pressure lowering effect of Ca irrespective of NaCl intake.

Blood pressure, electrolyte and adrenal responses in swim-trained hypertensive rats.

In order to test the effect of aerobic training on blood pressure, and to examine the putative mechanisms involved, stroke-prone spontaneously hypertensive rats (SHR-SP), borderline hypertensive rats (BHR), and Wistar-Kyoto control rats (WKY) were swim-trained for up to 1.5 h twice-daily for 22 weeks. The BHR were F1 back-cross SHR-SP, WKY. A training effect was observed in the trained rats compared to controls, as demonstrated by slower heart rates, heavier hearts and increased cytochrome oxidase activity in their skeletal muscle. Trained SHR-SP and BHR had significantly lower blood pressures at the end of the intervention period (approximately 10 mmHg) compared to controls. Acute increases in blood pressure with swimming were less in trained than in untrained rats. Trained rats had higher extracellular sodium values than untrained rats. Further, trained SHR-SP and BHR had lower intra-erythrocyte sodium values than controls. Increases in corticosterone, epinephrine and norepinephrine with swimming were less in trained rats than in controls. We conclude that exercise conditioning ameliorates hypertension in rats. The mechanism may involve an effect on cation transmembrane transport, as well as decreased, adrenosympathetic tone. Moreover, these effects may be related.

Intracellular sodium concentration and transport in red cells in essential hypertension, hyperthyroidism, pregnancy and hypokalemia.

UNLABELLED: Intracellular sodium content ([Nai]), ouabain-sensitive ('Na-K ATPase') and ouabain-insensitive ('passive permeability') sodium efflux, Na-K cotransport and Na-Li ('Na-Na') countertransport were estimated in erythrocytes in 39 control subjects, 20 patients with essential hypertension, 14 patients with hypokalemia of renal or unknown etiology, 13 hyperthyroid patients and 19 pregnant women. In normokalemic essential hypertension there was only a moderate, but significant elevation of the activity of the Na-Li countertransport system. In the group of patients with hypokalemia, there was a significant increase of [Nai], ouabain-insensitive sodium efflux and Na-Li countertransport. In hyperthyroidism, a marked decrease of Na-Li countertransport was associated with a marked elevation of [Nai], in pregnancy an elevation of the Na-Li countertransport with a [Nai] 43% lower than the control values. The ouabain-sensitive sodium efflux was elevated in hyperthyroidism and hypokalemia, in which [Nai] was increased. In the control subjects there was a positive linear correlation between ouabain-sensitive sodium efflux and [Nai]. The sodium component of the Na-K cotransport was decreased to about one third of the unchanged furosemide-sensitive potassium component during pregnancy. CONCLUSIONS: The changes of cellular sodium metabolism in essential hypertension are of minor degree as compared to those in the other conditions studied. Cellular sodium metabolism in blood cells is influenced by thyroid hormones and metabolic disorders. Na-Li countertransport, i.e. Na-Na countertransport, seems to be involved in the regulation of [Nai]: an increase of its activity diminishes [Nai] (pregnancy); a decrease elevates [Nai] (hyperthyroidism). Ouabain-sensitive sodium efflux, i.e. 'Na-K ATPase', is mainly regulated by its substrate, [Nai].

Peripheral effects of thyroid hormones: alteration of intracellular Na-concentration, ouabain-sensitive Na-transport, and Na-Li countertransport in human red blood cells.

To investigate the effect of thyroid hormones on erythrocyte cation transport systems and intracellular electrolyte content we have measured the activity of Na-K ATPase, Na-Li countertransport, as well as red cell sodium and potassium contents in patients with hyperthyroidism and in euthyroid controls. Intracellular Na- and K-concentrations were determined in erythrocytes washed three times in isotonic MgCl2 solution. Ouabain-sensitive Na-transport was estimated as the increase of Na before and after addition of ouabain in an erythrocyte suspension in isotonic Na-free medium. Na-Li countertransport was measured according to the method described by Canessa et al. [2]. The patients with hyperthyroidism exhibited a significantly elevated intracellular sodium content as well as a highly increased Na-K ATPase activity. Intracellular potassium content was not altered in the hyperthyroid subjects, but Na-Li countertransport was markedly decreased as compared to the controls. The results indicate that different ion transport systems of the erythrocyte membrane are influenced by thyroid hormones. We suggest that the elevation of Na-K ATPase activity might be due to the increased intracellular sodium concentration which is caused by the diminished countertransport pathway. Furthermore, the activity of Na-K ATPase, Na-Li countertransport, and intracellular sodium content in erythrocytes might be a useful peripheral indicator of thyroid hormone excess.

[Cation flux in erythrocytes of patients with essential hypertension]. / Kationenfluxe am Erythrozyten bei Patienten mit essentieller Hypertonie.

86Rubidium influx and Na--K-cotransport have been investigated in erythrocytes of mild essential hypertensives and normotensives devoid of familial hypertension. For measurement of cotransport Na-loaded/K-depleted erythrocytes were used while rubidium influx (with and without ouabain) was determined under physiological conditions. Both transport systems were linear in time, the interassay variances in a range of about 10%. The patients with essential hypertension exhibited a decreased rubidium influx compared to the normotensive controls. Ouabain-sensitive fluxes were not significantly different between the two groups, whereas ouabain-resistent rubidium influx was diminished in the group of the patients. Na--K-cotransport was also found to be decreased in essential hypertension. There was no correlation between cotransport and Rb-influx. The results indicate changes in cation fluxes in erythrocytes of essential hypertensives, the Na--K-cotransport being rather more altered than rubidium influx. It is speculated that hypertensive persons with reduced rubidium flux rates may represent a subpopulation of essential hypertension and that their high blood pressure may be additionally influenced by exogeneous factors e.g. enhanced sodium uptake.

Effect of cytotoxic drugs on the function of the hypothalamo-pituitary-adrenal axis.

We measured the serum concentration of thyroid-stimulating hormone (TSH), its response to exogenic TSH-releasing hormone (TRH), as well as cortisol plasma levels before and after stimulation with adrenocorticotrophic hormone in 15 patients before, during and after a chemotherapeutic cycle. 3/6 patients receiving only cytotoxic drugs developed a marked suppression of the TSH response to TRH and 1 of these patients showed an impairment of the adrenal function under chemotherapy. This was also observed in 7/9 patients receiving both cytotoxic drugs and corticosteroids; however, the individual pattern of the impairment was quite variable. 5/9 patients in this group developed a suppression of the TSH response to TRH. Impairment of the hypothalamo-pituitary-adrenal axis function under cytotoxic drugs and/or corticosteroids occurs with great variability and the mechanisms involved in its etiology are not yet fully understood.

[Plasma concentration and systemic effect of betamethasone after intra-articular injection (author's transl)]. / Plasmakonzentration und systemische Wirkung von Betamethason nach intraartikulärer Injektion.

Plasma concentrations of betamethasone, cortisol and corticosterone were measured before and after intraarticular injection of a betamethasone-depot preparation (Celestan-Depot) by radioimmuno-assay in 31 patients. Plasma concentration of betamethasone reached its maximum of between of 10 and 17 microgram/dl 30 min after injection. It had fallen to half after 2 hours, and practically to nil from the eighth day onwards. Lowest plasma levels of cortisol and corticosterone occurred after 6--24 hours, returning to the normal range after four days. In nine patients with knee-joint effusion and synovitis the plasma concentration of betamethasone was significantly higher after 24 hours, and cortisol and corticosterone values after 48 hours significantly more suppressed, than in patients without joint effusions and signs of inflammation. The results indicate that plasma concentration of betamethasone and the suppressant effect on the adrenal cortex after intra-articular injection is similar to that after intramuscular applications. Correspondingly, systemic application of the cortisol derivatives can cause significant side effects and be contra-indicated also after intra-articular injection.

Screening radioimmunoassay for aldosterone in preheated plasma without extraction and chromatography.

We directly estimated plasma aldosterone radioimmunologically with use of an antiserum raised against an aldosterone-3-oxime/bovine serum albumin conjugate, the estimation being on samples with and without heating (60 degrees C), and diluted and undiluted. Values so obtained were compared with those by radioimmunoassay after extraction and chromatography. The correlation--even negative values were obtained--was poorest when the steroid was directly estimated in nonheated, undiluted plasma. Correlations were best (r = 0.918) for preheated and diluted native plasma, and the interassay CV was 9.8% (n = 57). However, there were some extraordinarily high values. After equilibrium dialysis of native and preheated (60 degrees C) plasma (15 plasma samples), the percentages of apparent free aldosterone and cortisol increased from 51.4 +/- 2.6% (SEM) to 64.3 +/- 1.6% and from 11.5 +/- 2.2% to 61.1 +/- 1%, respectively. We conclude that aldosterone-binding proteins play a role in direct radioimmunoassays of aldosterone in plasma, but by heating (with or without diluting) the plasma, direct assay can be used as a simple, fast, and inexpensive screening method.

Dissociation in the excretion of different aldosterone metabolites and unmetabolized ('free') aldosterone in hypertension.

1. The determination of aldosterone-18-glucuronide (pH 1-labile aldosterone) was complemented by concomitant measurements of free urinary aldosterone and tetrahydroaldosterone in 307 patients, most of whom were hypertensive. In 38 cases (12.3%) the normal, aldosterone-18-glucuronide concentration was clinically misleading, but increased free aldosterone and/or tetrahydroaldosterone values suggested the presence of hyperaldosteronism, which in many of these cases was confirmed by elevated excretion of the possible major aldosterone precursor 18-hydroxycorticosterone (18-OH-B). 2. Of 224 patients with essential hypertension and normal or low plasma renin activity 18 had an elevated free aldosterone and/or tetrahydroaldosterone excretion without increased aldosterone-18-glucuronide. These cases may represent early or pre-symptomatic forms of primary hyperaldosteronism. In other cases, particularly when tetrahydroaldosterone was increased alone, abnormalities of aldosterone metabolism were suspected. 3. In two out of 15 patients with primary hyperaldosteronism, aldosterone-18-glucuronide values were frequently found to be normal, although elevations were noted in other variables. However, no relation to the morphological abnormality (adenoma versus hyperplasia) was seen.

Radioimmunoassay of free urinary 18-hydroxydeoxycorticosterone (18-OH-DOC) in patients with essential hypertension.

Specific antiserum was raised in white New Zealand rabbits using 18-hydroxydeoxycorticosterone-3-oxime-BSA complex as antigen. The urinary free 18-OH-DOC was estimated after dichloromethane extraction and separation in one paper chromatographic system (propylene glycol/toluene). The mean 18-OH-DOC excretion value (+/- S.D.) in normal subjects was 0.861 +/- 0.527 microgram/24 h (n=23). ACTH produced a 25-fold increase in the excretion of free 18-OH-DOC. Dexamethasone suppressed the values to the lower range of sensitivity. 32% of patients of essential hypertension showed a moderate increase in the free urinary 18-OH-DOC values. The mean value (+/- S.D.) in the low renin hypertension group was 2.50 +/- 1.49 microgram/24 h (n=19), in the normal renin patient group 1.84 +/- 1.22 microgram/24 h (n=38). The difference between controls and the hypertensive groups was statistically significant. Among the different hypertensive groups significant differences could not be calculated.

[Ossification of the auricle in partial pituitary failure with selective ACTH and STH deficiency (author's transl)]. / Verknöcherung der Ohrmuschel bei partieller Hypophyseninsuffizienz Mit selektivem ACTH- und STH-Mangel.

An acquired partial pituitary insufficiency of unknown origin with selective ACTH and STH deficiency was demonstrated in a 44-year-old patient. The clinical course over many years corresponds to subclinical Addison's disease with occasional acute crises. Ossification of both auricular cartilages and anhidrosis were outstanding signs. There is possibly a connection between the glucocorticoid deficiency over many years with normal mineralocorticoids and the auricular cartilage ossification.

Pharmacokinetic and pharmacodynamic studies of infusions with [Sar 1, Val5, Ala8] angiotensin II (saralasin).

A modification of the infusion test with saralasin, an angiotensin II antagonist for the detection of renin-dependent high blood pressure was studied in renal hypertensive rats and in normotensive and hypertensive subjects. Infusion was started at a rate of 0.01 microgram/kg x min saralasin and the dose was increased ten-fold at 15 min intervals. A significant fall of diastolic blood pressure was observed at the dose of 0.1 microgram/kg x min in renal hypertensive rats, in healthy subjects treated with diuretics, and in patients with renovascular hypertension (saralasin responders). Plasma concentrations of angiotensin I, angiotensin II and of saralasin as well as plasma renin activity were measured. At the lowest infusion rate of 0.01 microgram/kg x min, saralasin plasma levels were 40-fold higher than plasma angiotensin II levels. The decrease in arterial blood pressure occurred at lower doses of saralasin than the increase of plasma renin due to inhibition of feedback on the renin secreting cells. It is concluded that if the saralasin test is performed by a stepwise increase of the infusion rate, potentially dangerous complications such as hypo- or hypertensive reactions can be avoided. The diagnostic reliability is improved by such a procedure since false positive and false negative responses may be prevented. The pressor effect of saralasin in non-renin dependent patients is an advantage since it causes a more marked difference of blood pressure change between saralasin responders and non-responders.

Influence of D-thyroxine on plasma thyroid hormone levels and TSH secretion.

Triiodothyronine (T3), thyroxine (T4), basal TSH and TSH after stimulation with TRH were determined in healthy subjects and patients treated with D-thyroxine (DT4). After a dosage of 6 mg DT4 the D/L T4 plasma concentration rose about 4-fold 4 hours after application and was only moderately elevated 14 hours later. To achieve constantly elevated T4 levels 3 mg DT4 were applied in the further experiment every 12 hours. The D/L T4 plasma concentration rose 2.5-4-fold and there was a small but significant increase of the D/L T3 plasma concentration. 74 hours after onset of treatment basal TSH was below detectable limits and the increase of TSH 30 min after injection of 200 mug TRH (TRH test) was only about 15% compared to zero time. The time course of TSH suppression was investigated after treatment with DT4 and LT4 (single dosage of 3 mg). TRH-tests were performed before, 10, 26, 50 and 74 hours after the first dosage of D or LT4. There was no difference in the time course of basal TSH and TSH stimulated by TRH. In 10 patients on DT4 long-term therapy, basal and stimulated TSH were found to be below the detectable limits of 0.4 mug/ml. Our results show that (1) plasma half-life of DT4 is less than 1 day, (2) TSH suppression after D and LT4 treatment is very similar, and (3) in patients on long-term DT4 treatment, TSH plasma concentration is below detectable limits even after stimulation with TRH.

On the time course of thyrotropin suppression by high doses of thyroid hormones.

Basal and stimulated TSH decreased progressively. Basal TSH was suppressed below the detection limit of 0.4 muU/ml after 74 h in 2 of the T3 and all of the T4 treated individuals. At this time in both groups 3 individuals could be significantly stimulated by TRH (abour 5% of the pretreatment stimulation). There was no significant difference in the time course of suppression obtained by T3 or T4 through plasma T3 levels in the T4 treated group were considerably lower.