Epinephrine supports the postabsorptive plasma glucose concentration and prevents hypoglycemia when glucagon secretion is deficient in man

We hypothesized that adrenergic mechanisms support the postabsorptive plasma glucose concentration, and prevent hypoglycemia when glucagon secretion is deficient. Accordingly, we assessed the impact of glucagon deficiency, produced by infusion of somatostatin with insulin, without and with pharmacologic alpha- and beta-adrenergic blockade on the postabsorptive plasma glucose concentration and glucose kinetics in normal human subjects. During somatostatin with insulin alone mean glucose production fell from 1.5 +/- 0.05 to 0.7 +/- 0.2 mg/kg per min and mean plasma glucose declined from 93 +/- 3 to 67 +/- 4 mg/dl over 1 h; glucose production then increased to base-line rates and plasma glucose plateaued at 64-67 mg/dl over 2 h. This plateau was associated with, and is best attributed to, an eightfold increase in mean plasma epinephrine. It did not occur when adrenergic blockade was added; glucose production remained low and mean plasma glucose declined progressively to a hypoglycemic level of 45 +/- 4 mg/dl, significantly (P less than 0.001) lower than the final value during somatostatin with insulin alone. These data provide further support for the concept that maintenance of the postabsorptive plasma glucose concentration is a function of insulin and glucagon, not of insulin alone, and that adrenergic mechanisms do not normally play a critical role. They indicate, however, that an endogenous adrenergic agonist, likely adrenomedullary epinephrine, compensates for deficient glucagon secretion and prevents hypoglycemia in the postabsorptive state in humans. Thus, postabsorptive hypoglycemia occurs when both glucagon and epinephrine are deficient, but not when either glucagon or epinephrine alone is deficient, and insulin is present.

[Functional autonomic blockade in the diagnosis of functional sinus node disorders]

The influence of the autonomic nervous system on sinus node automatism was assessed in 61 patients with suspect sinus node dysfunction. Cardiac frequency and corrected sinus node recovery time (CSNRT) were determined before and after functional autonomic blockade with intravenously administered propranolol (0,2 mg/kg) and atropine (0,04 mg/kg). A pathologic CSNRT was found in 59% of patients before and in 54% after autonomic blockade. In 44% pathologic CSNRT occurred during both conditions. In these patients intrinsic sinus node disease can be assumed. In 15% of patients an initially pathologic CSNRT became normal after blockade. In these patients sinus node dysfunction is caused by autonomic dysregulation. In 10% of patients pathologic CSNRT was seen for the first time after blockade. In such patients an altered autonomic balance seems to camouflage the primary intrinsic sinus node disease. Abnormal intrinsic cardiac frequency (cardiac frequency after autonomic blockade) was observed in pathologic prolongation of CSNRT after blockade, however not in normal CSNRT. On the other hand only 39% of patients with prolonged CSNRT after blockade had at the same time an abnormal intrinsic cardiac frequency. Autonomic blockade improves the diagnosis of the sick sinus node syndrome. Demonstration of abnormal intrinsic cardiac frequency is highly specific of intrinsic sinus node disease. Normal intrinsic cardiac frequency does, however, not exclude intrinsic sinus node disease.

Effect of anti-inflammatory drugs on partitioning characteristics of propranolol and oxprenolol

The influence of a range of nine anti-inflammatory drugs on the octan-1-ol aqueous phosphate buffer pH 7.4 apparent partition coefficients of propranolol and oxprenolol has been examined. All produced a change in the apparent partition coefficient which can be explained in terms of partitioning of hydrophobic ion-pairs formed between the ionic anti-inflammatory compound and the protonated cationic drug.

Pancreatic polypeptide and gastrin release during sham feeding in man

During modified sham feeding (MSF) the role of endogenous gastric acid secretion and the influences of the autonomic nervous system on the release of pancreatic polypeptide (PP) and gastrin have been studied in 12 healthy subjects (aged 24-38 years). Sham feeding was performed without pretreatment (control) and after pretreatment with 400 mg cimetidine, 80 mg propranolol (both given orally) or 1 mg atropine administered subcutaneously 60 min prior to sham feeding. MSF induced a significant increase (about 100%) in PP release. Its early peak was reduced by pretreatment with propranolol whereas cimetidine had no effect. Atropine completely abolished the PP response. Gastrin release was stimulated by MSF only after prior administration of cimetidine and, to a lesser extent, after atropine pretreatment. It is concluded that: (1) the PP release after stimulation is under strong cholinergic control but is also mediated--particularly in the early phase--by adrenergic mechanisms; (2) endogenously released acid during vagal stimulation plays a minor role in the modulation of PP secretion, but (3) masks gastrin response to MSF.

The role of the autonomic nervous system on sinus node function in patients with intermittent sinoatrial block

Sinus node (SN) function was analyzed with and without autonomic blockade (AB) in 31 patients (mean age: 57.6 +/- 12.8) with intermittent sinoatrial block. Twenty-one patients had organic heart disease; in the remaining ten signs of underlying heart disease were not present. Nineteen patients had dizziness or syncope. Sinus cycle length, sinus rate, corrected sinus node recovery time (CSRT) and sinoatrial conduction time (SACT) were analyzed. After control measurements, AB was produced by i.v. propranolol (0.2 mg/Kg) and atropine (0.04 mg/Kg). Measurements of electrophysiological parameters were then repeated. After AB sinus rate and CSRT did not show statistically significant differences, whereas SACT decreased significantly (P less than 0.001). When intrinsic heart rate (IHR) was abnormal (11 cases), intrinsic CSRT was always abnormal, whereas when IHR was normal, intrinsic CSRT was normal in 11 patients and abnormal in nine. In several cases, when sinus rate increased after AB, CSRT decreased and vice-versa. The parameters of intrinsic SN function were normal in 80% of patients with a normal heart and only in 14.2% of patients with organic heart disease. These data indicate that: (1) during the control period SACT is mainly conditioned by the vagal tone; (2) abnormalities in control CSRT are not uniformly abolished after AB in patients with normal IHR; (3) AB has a differential effect on the two variables of SN automaticity; i.e. sinus rate and CSRT; and (4) in patients without underlying heart disease, the SN dysfunction is almost exclusively related to alterations of the autonomic nervous system.

Studies on the mechanisms of secondary pause after high rate atrial pacing

Atrial pacing up to 400 beats per minute (bpm) was performed in 20 open chest dogs. Measurements were made on the first five return cycles. Instances with the first cycle shorter than the basic cycle length were excluded. Secondary pauses (SP) were frequently observed at pacing rates equal to or faster than 280 bpm. Intravenous application of propranolol and atropine did not diminish SP, nor did bilateral vagotomy. Additional subthreshold stimuli, as well as stimulation with electrodes with large interpolar distance influenced neither the length of sinus node recovery time (SNRT) nor the SP phenomenon. Simultaneous pacing of the right atrium and right ventricle had no significant effects on SNRT and SP. Pacemaker shifts occurring frequently after high rate pacing were not necessarily accompanied by SP. The velocity of activation spread over the sinoatrial region was significantly slower (46.9 +/- 7.3 cm/s) in cases with SP than in those with primary pauses (PP) (72.5 +/- 8.1 cm/s). It was concluded that high rate induced SP was a feature indicating suppression of sinoatrial conduction.

Non-insulin-treated ICA positive and negative diabetics are equally insulin resistant

Insulin action was assessed in 5 cytoplasmic islet cell antibody (ICA) positive non-diabetics, 8 ICA positive (type I) non-insulin-treated diabetics, 7 ICA negative insulin-treated diabetics by measurement of steady state plasma glucose (SSPG) levels during a combined intravenous infusion of propranolol, adrenaline, glucose and insulin. SPPG values of ICA positive and negative non-diabetics were similar and their combined value (4.0 +/- 0.5 mmol/l) was significantly lower (p less than 0.01 and less than 0.01) than those (11.5 +/- 1.9 and 11.3 +/- 2.2 mmol/l) of ICA positive and negative diabetics, indicating that both groups of diabetics were similarly insulin resistant. Similar correlations were observed between SSPG and HbA1 levels when considering all ICA positive subjects (r = 0.89, p less than 0.001) and all ICA negative subjects (r = 0.73, p less than 0.01). Conventional insulin treatment (2.6 months) in 4 ICA positive diabetics improved insulin action in each case with a reduction in mean SSPG concentration from 14.0 +/- 2.3 to 8.5 +/- 3.4 mmol/l. Thus, ICA positive and negative diabetics, of equivalent degree of carbohydrate intolerance, are equally insulin resistant. Insulin treatment may improve, but appears not to normalise, insulin action in ICA positive (type I) diabetics.

Direct alpha-adrenergic stimulation of hepatic glucose production in human subjects

Six normal humans each underwent infusions of 1) saline; 2) propranolol; 3) somatostatin; 4) somatostatin with propranolol; and 5) somatostatin with propranolol plus phentolamine on separate occasions. Propranolol alone had no effect on glucose production or plasma glucose. Somatostatin alone produced the expected initial decrease followed by an increase in both hepatic glucose production and plasma glucose. beta-Adrenergic blockade with propranolol displaced the glucose production (MANOVA, P = 0.0220) and plasma glucose (MANOVA, P = 0.0057) somatostatin response curves to higher levels, whereas alpha-adrenergic blockade with phentolamine combined with beta-adrenergic blockade displaced the glucose production (MANOVA, P = 0.0281) and plasma glucose (MANOVA, P = 0.0134) somatostatin response curves to lower levels. Because plasma insulin, C-peptide, and glucagon were suppressed comparably under all three conditions and plasma glucose concentrations were comparable initially, this represents direct alpha-adrenergic stimulation of hepatic glucose production in postabsorptive humans demonstrable when the primary glucoregulatory hormones are withdrawn and beta-adrenergic mechanisms are blocked. It is best attributed to sympathetic neural norepinephrine release.

The effect of different surface chemical groups on drug binding to liposomes

The binding of four secondary and tertiary amine drugs with local anesthetic activity (propranolol, tetracaine, lidocaine, procaine) to liposomes containing charged surface groups of different chemical composition has been investigated. Binding is determined by measurement of partition coefficients and of drug induced zeta potential changes of the liposomes. For propranolol 30% of the total amount of drug dissolved in phosphatidylcholine is located as protonated form in the liposome surface. Fifty percent of tetracaine and 13% of procaine contribute to the surface charges. Negative surface charges (phosphatidylserine) facilitate drug binding and drug protonization in the liposome surface. Positive surface charges (hexadecyltrimethylammonium) prevent the protonization of the drugs. Different chemical groups of single negatively charged phospholipids or of electrostatically neutral lipids have no significant effect on drug binding which proves that binding is not influenced by steric and bulky head group configurations. The drugs interact hydrophobically with the lipid phase in such a way that the drug amine protonizes in the presence of the negatively charged phosphate oxygen of the phospholipid. Hexadecanoic acid is located deeper within the liposome surface than other negatively charged phospholipids. Correspondingly the drug action is weaker and drug protonization is prevented.

Reproducibility of electrophysiological parameters of sinus node following autonomic blockade

We investigated the reproducibility of sinus node cycle length (SCL), corrected sinus node recovery time (CSRT) and sino-atrial conduction time (SACT) during the control state and following autonomic blockade in 25 patients (mean age: 56.9 +/- 13.8 years). Autonomic blockade was induced by i.v. administration of propranolol (0.2 mg/kg) and atropine (0.04 mg/kg). The electrophysiological study was repeated after 24 hr and the results were compared. The patients were divided into two groups: Group 1 (15) with normal and Group 2 (10) with abnormal intrinsic sinus node function. Following autonomic blockade in Group 1 the daily variations in SCL, CSRT and SACT were very slight whereas in Group 2 there was far greater variability in these parameters. However, in the latter group there were no patients who changed their status from prolonged to normal intrinsic CSRT on the second study, whereas SACT changed its status in 2 patients. In Group 1 the daily variations in sinus node parameters were much slighter following autonomic blockade than during the control state. In Group 2 the variations were very similar during control and following autonomic blockade. These data suggest that: (1) following autonomic blockade the reproducibility of sinus node parameters is very good in Group 1, whereas in Group 2 several patients show marked daily variations in sinus node parameters; (2) following autonomic blockade the sinus node electrophysiological parameters are meaningful in diagnosing an involvement of intrinsic sinus node function; and (3) in patients with abnormal sinus node parameters during control state, but with normal intrinsic sinus node function, the daily variations are mainly due to change in autonomic tone, whereas when the intrinsic sinus node function is abnormal, the day to day variations during control state appear due predominantly to intrinsic sinus node abnormalities.

Regulation of ketonaemia in hyperthyroidism: study of the role of free fatty acids

We have indirectly assessed the role of free fatty acids (FFA) and of hepatic ketogenesis in the regulation of ketone body levels in euthyroid and hyperthyroid subjects. All studies were performed under controlled dietary conditions (35 and 45 kcal/kg body weight/day respectively for euthyroid and hyperthyroid subjects). In the post-absorptive state hyperthyroid patients had normal, glucagon levels and, in spite of increased insulinemia (p less than 0.02), elevated concentrations of blood glucose (p less than 0.01), glycerol (p less than 0.001) and ketone bodies (p less than 0.05). In the face of this hyperketonaemia, there was no significant increase of plasma FFA, suggesting possible increased hepatic conversion of FFA to ketone bodies. However, when FFA were acutely raised to high levels, the induced rise of ketone bodies was similar in hyperthyroid and euthyroid subjects. Oral propranolol administration to hyperthyroid patients in the post-absorptive state decreased the concentrations of glycerol (p less than 0.05) and ketone bodies (p less than 0.05) without altering insulin concentrations. Ketone bodies fell without any significant decrease of FFA suggesting a possible direct effect of propranolol administration on hepatic ketogenesis. However, the ketone body response to raised FFA levels was unaffected by propranolol. We have evidence in hyperthyroid patients of increased lipolysis and ketogenesis in spite of increased daily caloric intake. These results suggest that these metabolic abnormalities are not merely due to relative starvation. We have tentative evidence for modification of the intra-hepatic conversion of FFA to ketone bodies in the post-absorptive state but no supporting evidence when FFA levels were experimentally raised.

[The L-DOPA-propranolol test for the evaluation of reserves in secretory growth hormone]

The growth hormone (GH) reserve of 75 short probands (age 1.9 to 23.8 years) was evaluated on the basis of oral L-dopa (300 mg/m2) and propranolol (0.75 mg/kg) administration. The GH response was normal in 21 probands (20.9 +/- 1.24 ng/ml; means +/- SEM) and was found to be higher than the response to the insulin or arginine test. 39 patients failed to respond (less than 6 ng/ml) and were diagnosed as GH deficient. In 15 cases an "intermediate" response (greater than 6 less than 12 ng/ml) was found and in these patients partial GH deficiency was assumed. There was not a single false positive result with this test, which cannot be said for any of the other commonly-used stimulation tests. In two children hypoglycaemic blood glucose levels were observed during the test, whilst in one case loss of consciousness and convulsions were seen. In four patients the test had to be interrupted because of side effects. These children had the following findings in common: GH deficiency was confirmed and the patients were still very young and basal blood glucose levels were relatively low at the beginning of the test. The L-dopa-propranolol test is an effective and reliable GH stimulation test, but severe side effects may occur.

Effects of beta-blockade on glycogen metabolism in human subjects during exercise

The effect of beta-blockade on glycogen metabolism during isometric and dynamic exercise in humans has been investigated. Isometric exercise increased the glycogenolytic rate in muscle but had no effect on the cAMP content. Neither the metabolic pattern nor the time of contraction was affected by beta-blockade. Dynamic exercise increased the cAMP content in muscle by about 100%. The cAMP content at rest was significantly reduced after propranolol infusion and did not increase during exercise. Total hexosemonophosphates increased sixfold during exercise but little or no increase occurred after administration of propranolol. The accumulation of lactate in muscle was slightly reduced during exercise following beta-blockade. The fraction of phosphorylase in the alpha form was 22.5% of the total at rest but decreased to 16% at exhaustion. Synthetase I was similarly decreased. During exercise with propranolol phosphorylase alpha decreased further to 3%, whereas synthetase I was unchanged. It is concluded that beta-blockade has no effect on muscle glycogenolysis during isometric contraction but decreases the rate of glycogen degradation during dynamic exercise at high work loads due to changes in the phosphorylase-synthetase system.

Mechanisms of postprandial glucose counterregulation in man. Physiologic roles of glucagon and epinephrine vis-a-vis insulin in the prevention of hypoglycemia late after glucose ingestion

The transition from exogenous glucose delivery to endogenous glucose production late after glucose ingestion is not solely attributable to dissipation of insulin and, therefore, must also involve factors that actively raise the plasma glucose concentration--glucose counterregulatory factors. We have shown that the secretion of two of these, glucagon and epinephrine, is specific for glucose ingestion and temporally related to the glucose counterregulatory process. To determine the physiologic roles of glucagon and epinephrine in postprandial glucose counterregulation, we produced pharmacologic interventions that resulted in endogenous glucagon deficiency with and without exogenous glucagon replacement, adrenergic blockade, and adrenergic blockade coupled with glucagon deficiency starting 225 min after the ingestion of 75 g of glucose in normal subjects. Also, we assessed the effect of endogenous epinephrine deficiency alone and in combination with glucagon deficiency late after glucose ingestion in bilaterally adrenalectomized subjects. Glucagon deficiency resulted in nadir plasma glucose concentrations that were approximately 30% lower (P less than 0.01) than control values, but did not cause hypoglycemia late after glucose ingestion. This effect was prevented by glucagon replacement. Neither adrenergic blockade nor epinephrine deficiency alone impaired the glucose counterregulatory process. However, combined glucagon and epinephrine deficiencies resulted in a progressive fall in mean plasma glucose to a hypoglycemic level late after glucose ingestion; the final glucose concentration was 40% lower (P less than 0.02) than the control (epinephrine deficient) value in these patients, and was nearly 50% lower (P less than 0.001) than the control value and approximately 30% lower (P less than 0.05) than the glucagon-deficient value in normal subjects. We conclude (a) the transition from exogenous glucose delivery to endogenous glucose production late after glucose ingestion is the result of the coordinated diminution of insulin secretion and the resumption of glucagon secretion. (b) Epinephrine does not normally play a critical role in this process, but enhanced epinephrine secretion compensates largely and prevents hypoglycemia when glucagon secretion is deficient.

A central role for the polyamines in the aetiology of schizophrenia

The general consensus of opinion in psychopharmacology is that the basic lesion in schizophrenia is a defect of the dopaminergic mechanism in some part or parts of the brain. In this article I wish to show that there is sufficient evidence to indicate that the central lesion involves the polyamines rather than dopamine.

Effects of nonselective and beta-1-selective blockade on glucose metabolism and hormone responses during insulin-induced hypoglycemia in normal man

The effects of nonselective beta-blockade (propranolol) and beta-1-selective blockade (atenolol) on glucose metabolism during insulin-induced hypoglycemia were studied in eight normal subjects during constant infusion of 3-[3H]glucose. Propranolol and to a lesser extent atenolol prolonged the hypoglycemic response to insulin. After maximal hypoglycemia a significant increase in glucose uptake rate was seen after propranolol and a corresponding trend was found in the atenolol experiments. The two beta-blockers did not influence glucose production rate after insulin administration. FFA concentration declined rapidly after insulin. Propranolol delayed the subsequent normalization of FFA whereas atenolol had no significant effect. Propranolol increased epinephrine and GH responses to hypoglycemia, whereas atenolol had no effect. Neither of the two beta-blockers influenced the concentrations of glucagon, norepinephrine, and PRL. It is concluded that nonselective beta-blockade prolongs the hypoglycemic response to insulin through an increased tissue uptake of glucose which is not counteracted by an increased glucose production. It is suggested that nonselective beta-blockade increases muscle glucose uptake by lowering FFA concentrations. beta-Blocker inhibition of the antiinsulin effect of epinephrine on glucose uptake in muscle can, however, not be excluded.

[Hyperventilation as a method of detecting atrioventricular conduction disorders in athletes]

A hyperventilation test, rationed with respect to respiratory rate and duration, was performed in 140 athletes under electrocardiographic control. During the test, one athlete developed an episode of sino-auricular block, and four showed a temporary second-degree Wenkebach--Samoilov A--V block. In three of those, resting ECG demonstrated decelerated atrioventricular conductivity which was combined with signs of myocardial dystrophy in two cases and with periodically recorded coronary sinus rhythm in one. Two athletes were under long-term dispensary observation. When repeated tests were negative, the block developed in response to hyperventilation preceded by obsidan administration.

[Changes in the systemic and regional circulation responses to immobilization stress in the rat after pharmacological sympathectomy]

A preliminary pharmacological desympathization (pirroxan, obzidan, ornid) decreased blood pressure, heart rate, cardiac output, and increased total vascular resistance in immobilized rats. The fraction of cardiac output decreased in lung (bronchial blood flow), liver and myocardium and increased in other organs and tissues. Relative blood supply increased in expansive regions of the skin, muscles and splanchnic organs but decreased in the liver. Opposite changes of transcapillary permeability were found in vascular regions of the skin and skeletal muscles as well as in splanchnic organs.

Sustained ventricular tachycardia after repair of tetralogy of Fallot: new electrophysiologic findings

Ventricular arrhythmia originating from the outflow tract of the right ventricle is a presumed cause of late sudden death in patients after repair of tetralogy of Fallot. Exercise testing has been shown to enhance detection, and phenytoin has been shown to control ventricular arrhythmias in these patients. This study reports new findings in 3 patients who underwent electrophysiologic studies at postoperative cardiac catheterization; in each, sustained ventricular tachycardia was induced and found to originate from the inflow-septal area of the right ventricle. Using serial studies, the same sustained ventricular tachycardia was induced during therapeutic serum concentrations of phenytoin but not after propranolol. No patient had ventricular arrhythmia during a 24-hour electrocardiogram or during exercise. Although no patient had normal hemodynamic function, only 1 patient had right ventricular pressure greater than two-thirds systemic pressure. Each patient had undergone initial intracardiac repair at a relatively late age (3, 9, and 9 years).

Control of pulsatile insulin secretion in man

Plasma insulin and glucose concentrations were examined in man in a basal state from central venous samples taken at 1-min intervals for up to 2.5 h. Normal subjects have insulin oscillations of mean period 14 min (significant autocorrelation, p less than 0.0001) with changes in concentration of 40% over 7 min. The pulsation frequency was stable through cholinergic, endorphin, alpha-adrenergic or beta-adrenergic blockade, or small perturbations with glucose or insulin. Stimulation of insulin secretion by intravenous glucose, tolbutamide or sodium salicylate increased the amplitude of the insulin oscillations while the frequency remained stable. Patients with a truncal vagotomy or after Whipple's operation had longer-term oscillations of 33 and 37 min periodicity (autocorrelation: p less than 0.0001), with insulin-associated glucose swings four times larger than those of normal subjects. Type 2 (non-insulin-dependent) diabetic patients had a similarly increased insulin-associated glucose swing of six times that seen in normal subjects. The hypothesis is proposed that the 14-min cycle of insulin production is controlled by a 'pacemaker' which assists glucose homeostasis. The longer 33-37-min oscillations, seen in those with denervation, may arise from a limit-cycle of the feedback loop between insulin from the B cells and glucose from the liver. The vagus may provide hierarchical control of insulin release.