Plasma inactive renin in patients with hyperthyroidism

Active and inactive PRA were measured after 1 h at rest in 16 normal controls and 20 patients with hyperthyroidism. In some of the patients these measurements were repeated after they had become euthyroid or received 90 mg propranolol for 1 week. Inactive PRA was determined as the difference between total PRA after trypsin activation and active PRA. Active PRA was significantly higher (P less than 0.01) in untreated patients than in normal subjects; however, the inactive PRA of patients was not different compared with that of normal subjects. Active PRA was normalized, and inactive PRA did not change after achievement of euthyroidism. The proportion of active of total PRA was significantly correlated with the levels of serum thyroid hormones (T3 and T4) in hyperthyroid patients (r = 0.46; P less than 0.05 and r = 0.55; P less than 0.01, respectively). The administration of propranolol reduced active PRA (P less than 0.05) and increased inactive PRA slightly but not significantly. These results indicate that in hyperthyroidism, the in vivo conversion of inactive renin to active renin is probably facilitated by increased sympathetic activity.

[A case of leprechaunism]

The authors report the case of an term infant weighing 2,860 kgs, who presented with failure to thrive during the two first months of life. Clinical features suggested the diagnosis of leprechaunism. After a review of the literature, the authors conclude that the diagnosis of this rare condition is essentially a clinical one, as there are no specific laboratory tests.

Protective effect of disodium cromoglycate on propranolol challenge

The protective activity of cromoglycate in histamine and propranolol bronchial provocation tests was studied in seven asthmatic patients by inhalation of increasing doses of histamine and propranolol in the absence and presence of inhaled cromoglycate. Cromoglycate showed a significant protective effect on the propranolol challenge, whereas no protection against histamine challenge could be observed.

Compatibility of propranolol hydrochloride injection with intravenous infusion fluids in plastic containers

The visual and chemical compatibility of propranolol hydrochloride injection admixtures in large-volume parenteral solutions (LVPs) packaged in plastic containers was studied. Propranolol hydrochloride injection was mixed with five different LVPs manufactured by three suppliers and packaged in plastic containers. Two concentrations (0.5 and 20 micrograms/ml) were tested. Samples were obtained via administration sets with 0.2-micron final filters. Visual appearance, pH, and propranolol hydrochloride concentration (HPLC method) of the admixtures were evaluated at 0, 4, 8, and 24 hours after preparation at room temperature and with ambient lighting. No change in visual appearance was observed. The pH of the admixtures ranged from 3.9 to 6.4, depending on the composition of the intravenous infusion fluid and propranolol hydrochloride concentration. There was no significant loss in potency during the test period. Additionally, there was no adsorption of propranolol hydrochloride onto the surface of polyvinyl chloride bags or polyolefin containers, or onto the filters. Propranolol hydrochloride can be mixed with common intravenous infusion fluids for 24 hours without compatibility problems when administered under normal conditions.

Evaluation of insulin resistance in non-obese subjects with impaired glucose tolerance

Insulin resistance was estimated in nine subjects with impaired glucose tolerance (IGT) and eleven healthy, age and body-weight matched controls. Glucose tolerance and insulin response were evaluated by means of a 2h-glucose infusion test. Insulin resistance was determined by measuring the steady state plasma glucose response (SSPG) to a continuous infusion of glucose (6 mg . kg-1 . min-1 or 12 mg . kg-1 . min-1), insulin, epinephrine and propranolol for 150 minutes as described previously by other authors. The endogenous insulin secretion (C-peptide) was inhibited by epinephrine and propranolol in controls and subjects with IGT irrespective of a low (6 mg . kg-1 . min-1) or high (12 mg . kg-1 . min-1) glucose infusion. Steady-state plasma levels of exogenous insulin were virtually identical in all groups studied. There were no significant differences in the pancreatic glucagon, growth hormone, FFA and glycerol response during the SSPG period between controls and subjects with IGT. In comparison to controls the mean SSPG was significantly higher in subjects with IGT (during low and high glucose infusion) suggesting the existence of insulin resistance in these subjects. A higher glucose dose as described earlier by other investigators does not provide a better discrimination of controls and subjects with IGT concerning their degree of insulin resistance. Finally, there was a direct correlation between the SSPG and glucose tolerance in the total group. In conclusion, our results have confirmed the validity of an infusion technique of glucose, insulin, epinephrine and propranolol for evaluation of insulin sensitivity in vivo. In addition, our findings have added further support for insulin resistance in subjects with IGT which is directly proportional to the degree of glucose intolerance.

Sympathetic supraspinal control of venous membrane potential in spontaneous hypertension in vivo

To clarify the mechanisms controlling mesenteric venous membrane potential (Em) in spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY), Em was measured in vivo using flexibly mounted glass microelectrodes. Venous diameters were also measured. Ems under control conditions were significantly less in SHR. alpha-Adrenergic blockade with phenoxybenzamine (PBZ) significantly dilated and hyperpolarized SHR small veins but failed to alter the membrane potential of WKY small veins. After blockade with PBZ, membrane potentials were similar in both strains. Propranolol suffusion failed to alter the SHR membrane potential but depolarized WKY small veins. During blockade with PBZ, propranolol depolarized venous membranes equally in both strains. Membrane potentials after spinal section were similar in both strains and equal to the Ems during total adrenergic blockade. The data indicate that, in SHR, the relatively depolarized Em derives from altered alpha-adrenergic input. In SHR, alpha-adrenergic input appears to exert its depolarizing effect, at least in party, by interfering with the expression of endogenous, beta-adrenergic hyperpolarization. The beta-adrenergic influence, like the alpha-adrenergic input in SHR, is dependent on intact supraspinal pathways.

A comparative study of beta-adrenoceptors in human and porcine lung parenchyma strip

1. Responses to (+/-)-isoprenaline (Iso), (-)-adrenaline (Adr) and (-)-noradrenaline (NA) were compared in isolated preparations of human and porcine lung parenchyma strip. 2. The order of relaxant potencies of these catecholamines in both human and porcine lung parenchyma was Iso greater than Adr greater than NA (1:0.24:0.01, human; 1:0.21:0.01.pig). These results suggest that beta 2-adrenoceptors predominate in both types of lung parenchyma strip. 3. pA2 values for the beta-adrenoceptor antagonist, propranolol (non-selective), with Iso as the agonist, in human and porcine lung strips were 7.84 and 7.83 respectively and for atenolol were 6.50 and 5.35 respectively. Taken as a whole results indicate the existence of an apparently homogeneous population of beta 2-adrenoceptors in porcine parenchyma strip, while both beta 1 and beta 2-adrenoceptors were revealed in human lung parenchyma.

Release and clearance rates of epinephrine in man: importance of arterial measurements

Previous estimates of catecholamine kinetics in human subjects have been based on the measurement of the catecholamine levels in forearm venous plasma. However, the use of forearm venous measurements may introduce considerable error, since venous catecholamine levels may primarily reflect metabolism in the organ drained rather than in the total body. In this study, arterial levels of epinephrine were found to significantly exceed forearm venous levels, both basally (mean +/- SEM, 71 +/- 13 vs. 50 +/- 7 pg/ml; n = 6; P less than 0.05) and during infusions of epinephrine [0.1 microgram/min (112 +/- 9 vs. 77 +/- 11 pg/ml; P less than 0.005) or 2 micrograms/min (862 +/- 71 vs. 437 +/- 66 pg/ml; P less than 0.001)]. During the 2 micrograms/min epinephrine infusion, arterial plasma norepinephrine rose from 191 +/- 37 to 386 +/- 78 pg/ml (P less than 0.001), while venous norepinephrine levels did not change significantly. Fractional extraction (arterial - venous + arterial X 100) of epinephrine across the forearm was 26 +/- 8% in the basal state and increased to 33 +/- 6% and further to 51 +/- 4% during the epinephrine infusions. The addition of propranolol (5 mg, iv, plus an 80 micrograms/min infusion) reduced fractional extraction from 51 +/- 4% to 35 +/- 5%. Whole body clearance of epinephrine, calculated from arterial measurements, was 33 +/- 3 ml/kg . min during the 0.1 microgram/min infusion and 35 +/- 3 ml/kg . min during the 2 micrograms/min epinephrine infusion, values 50% lower than the clearance rates calculated from venous measurements. Propranolol infusion resulted in a fall in whole body clearance to 20 +/- 2 ml/kg . min (P less than 0.001), suggesting that epinephrine clearance is partly dependent on a beta-adrenergic mechanism. Basal endogenous release rate (clearance X basal epinephrine level) was estimated to be approximately 0.18 microgram/min, a value much less than that reported in studies using venous measurements. We conclude that arterial rather than venous measurements should be used to estimate catecholamine kinetics in vivo.

Exercise testing in mitral valve prolapse before and after beta blockade

Exercise electrocardiograms must be interpreted with the understanding that not every positive test is indicative of coronary artery disease. Mitral valve prolapse mimics coronary heart disease clinically and often in the electrocardiographic response to exercise. Twelve patients with mitral valve prolapse in whom exercise testing was positive underwent a repeat study after beta blockade. All tracings returned to normal after adequate blockade, evidenced by 17 to 22% reduction of resting and exercise heart rates. To the best of our knowledge, this is the first such report in the English literature. The results of this study suggest that an exercise test after beta blockade should become part of the routine procedure in such patients. The elimination of false positive electrocardiographic responses by beta blockade should help improve the specificity of the exercise test. Moreover, similar responses should lead to the suspicion of mitral valve prolapse.

Baroreflex control of heart rate in humans during nitroprusside-induced hypotension

The baroreflex control of heart rate was investigated on 10 informed human subjects during light halothane anesthesia (0.3-0.5%, inspired concentration). The relationship of systolic pressure (SP) to the succeeding pulse interval (PI) was evaluated on a beat-to-beat basis during the entire course of sodium nitroprusside (SNP) depressor test. The initial slope of SP-PI plot (dPI/dSP) was used as an index of the sensitivity of baroreflex control of heart rate. Following an injection of SNP (4-6 micrograms/kg), dPI/dt was related directly to dPI/dSP, whereas the latter was inversely correlated with dSP/dt. The recovery of PI lagged behind that of SP, and there was a hysteresislike loop on the SP-PI plot. The time lag of PI recovery and the loop of SP-PI plot were markedly decreased by propranolol treatment and significantly increased by atropine. The slopes of SP-PI plot were significantly decreased by atropine but relatively unaffected by propranolol. These results indicate that SNP-induced hypotension in man during halothane anesthesia is associated with a withdrawal of parasympathetic inhibition and an enhancement of sympathetic activity. The autonomic control of heart rate in response to rapid changes in arterial pressure induced by SNP is dominated by parasympathetic influence; the more persistent sympathetic activity only becomes evident when the parasympathetic influence subsides quickly as the arterial pressure stays relatively constant at a new level. The slope of SP-PI plot (dPI/dSP) and the ratio of dPI/dt to dSP/dt during the decreasing pressure phase of SNP test can be used as indices for the sensitivity of baroreflex control of heart rate.

The binding of spin-labeled propranolol and spin-labeled progesterone by orosomucoid

The binding of the spin-labeled propranolol and spin-labeled progesterone to human orosomucoid has been studied as a function of temperature by electron spin resonance (ESR) techniques. At 20 degrees C the association constants are 1.9 x 10(6) and 4.9 x 10(5) M-1, respectively. In each case, the binding is competitive with unlabeled ligand. Above about 50 degrees C the apparent association constant for both ligands decreases rapidly with increasing temperature. This is due to thermal denaturation of the orosomucoid, as was shown independently by ultraviolet absorption spectroscopy and differential scanning calorimetry. Below the denaturation region the number of binding sites per orosomucoid molecule remains constant at approx. 1. Examination of the thermodynamic parameters shows the progesterone binding at 37 degrees C to be essentially enthalpically driven, while the propranolol binding at 37 degrees C has a substantial entropic component.

[Transient sinus node arrest-a dysregulation of the autonomic nervous system (author's transl)]

Electrophysiologic studies had been performed before and after pharmacologic autonomic blockade (propranolol 0.2 mg/kg and atropine 0.04 mg/kg body weight) in a 23-year-old female patient with documented sinus arrest of 27 sec duration. Normal electrophysiologic findings before and after autonomic blockade excluded intrinsic sinus node dysfunction. Sinus arrest is therefore though to be due to an intermittent dysregulation of the autonomic nervous system.

Responses of active and inactive plasma renin and changes in urinary kallikrein and plasma prekallikrein to various conditions in normal subjects

Little is known about changes in inactive plasma renin in various conditions or the in vivo activation mechanism of inactive renin. The effects of various factors known to stimulate or suppress renin release on active and inactive PRA were examined in normal subjects. Inactive PRA was determined as the difference between the total PRA after trypsin activation and active PRA. Concurrent measurements of urinary kallikrein excretion and plasma prekallikrein activity were performed to assess the possible role of renal or plasma kallikrein in in vivo activation of inactive renin. Short term stimulation with iv furosemide and ambulation, infusion of isoproterenol, and administration of captopril increased active PRA, but had little or no effect on inactive PRA. Sodium restriction and sodium loading, each for 4 days, induced parallel changes in active and inactive PRA. The administration of propranolol for 4 days decreased active PRA but did not change inactive PRA. There were no significant correlations between the changes in urinary kallikrein excretion and those in active PRA or in the proportion of active to total PRA after any short term treatments, except furosemide administration. Plasma prekallikrein activity was correlated with the proportion of active renin only during the long term sodium balance study. The present data suggest that the mechanisms ofr the control of inactive and active renin are different. Neither renal nor plasma kallikrein seems to be consistently involved in the in vivo activation of inactive renin.

Plasma guanosine 3',5'-monophosphate responses to methacholine and epinephrine in humans

The im injection of methacholine into healthy volunteers caused a dose-dependent increase in plasma cGMP levels; this increase was antagonized by atropine, while it was not affected by phentolamine or propranolol. The im injection of epinephrine caused a small but significant rise in plasma cGMP concentrations; this rise was completely blocked by the simultaneous injection of phentolamine, while it was not affected by atropine or propranolol. These data show that changes in the plasma concentration of cGMP may reflect not only cholinergic but also alpha-adrenergic functions in humans.

[Problems of so-called functional ECG changes]

It is reported on a 25-year-old African student with healthy heart in whom on account of an enlarged hepatologic diagnostics considerable changes of the ECG with repeated alteration between the ST-elevations and the T-negativations became manifest in the anterolateral BW-leads. In the otherwise inconspicuous findings functional changes of the ECG (early repolarization syndrome) with pronounced vegetative lability are concerned. The influence on the changes of the ECG by sympathicomimetics (isoproterenol test) may help to alleviate the diagnostics. In connection with diagnostic interventions the recognition and correct explanation of such ECG-findings is of decisive importance.

Effects of atropine on the cardiac arrest induced by propranolol and digitoxin in dogs

The present study examines the hypothesis that vagal activity can accelerate the onset of cardiac arrest produced by administering a beta-adrenergic blocking dose of propranolol to digitoxin-intoxicated dogs. In 11 experiments, intravenous injection of 0.75 mg/kg propranolol into digitoxin intoxicated dogs induced a sustained ventricular asystole (early-phase cardiac arrest). In six of these eleven experiments, intermittent pacing of the ventricles for as long as 150 min to maintain blood pressure after the onset of asystole, led to the resumption of spontaneous heart beats in only one dog. In five other experiments, injection of atropine (1 mg/kg) three min after the onset of early-phase cardiac arrest elicited sustained spontaneous junctional rhythms. In another four experiments the injection of atropine prior to or simultaneously with propranolol prevented the occurrence of asystole and caused the emergence of a junctional pacemaker. In eight experiments in which the cardiac arrest was reversed or prevented, injection of maintenance doses of atropine and propranolol caused eventual failure of the junctional pacemaker (late-phase cardiac arrest). This failure could not be prevented or reversed by atropine. The results suggest that early-phase cardiac arrest is due to vagal suppression of cardiac pacemakers and therefore supports the above hypothesis.

Potassium disposition and neuroendocrine effects of propranolol, methyldopa and clonidine during dynamic exercise

In order to determine the changes in potassium disposition with antirenin, antihypertensives during dynamic physical activity, a double-blind placebo controlled study was undertaken using normal volunteers receiving placebo or single and multiple dose clonidine, methyldopa and propranolol 0.2 mg. followed by 0.1 mg. bid x 7 days, 500 mg. followed by 250 mg. bid x 7 days or 80 mg. followed by 40 mg. bid x 7 days, respectively. Prior to study, 2 hours post dosing and coincident with immediate pre-exercise on treadmill, at graded increases of exercise and 2 hours post exercise (approximately 4 hours post dosing), blood was sampled for potassium, renin concentration, aldosterone and catecholamines. Blood pressure (BP) and heart rate (HR) were measured. The results demonstrate no greater increase in potassium over placebo with single or multiple dose clonidine or methyldopa. Following the initial dose of propranolol, 80 mg., there was a statistically greater rise in potassium over that seen with placebo but not observed with multiple dose. This may be related to the low multiple dose regimen. There were minor but significant changes in norepinephrine, renin and systolic pressure with multiple dose clonidine and methyldopa and in renin, heart rate and systolic and diastolic pressure with propranolol. Overall, the adrenergic responses, to exercise with methyldopa and propranolol are more biochemically altered than functionally impaired, yet the latter is related to dose and the underlying age and state of health of the group being studied.