Effects of glucagon on adenosine 3',5'-monophosphate and guanosine 3',5'-monophosphate in human plasma and urine

Urinary excretion of cyclic nucleotides and principal electrolytes in healthy humans of different ages

Urinary excretion of cyclic AMP, cyclic GMP, inorganic phosphorus, calcium, sodium, potassium and creatinine was measured in 138 healthy male and 104 healthy female humans from 2 to 68 years old. The range of cyclic nucleotide excretion was as follows: cyclic AMP (mumol/day), 1.01-10.89; cyclic GMP (mumol/day), 0.13-2.00; cyclic AMP (mumol/g creatinine), 1.52-8.93; cyclic GMP (mumol/g creatinine), 0.11-1.87. The 242 volunteers were grouped into seven classes according to age: A, 2-9 years old; B, 10-19; C, 20-29; D, 30-39; E, 40-49; F, 50-59 and G, 60-68. Average excretion (mumol/day) of cyclic AMP in class A (2.62 +/- 0.29 for males and 2.30 +/- 0.18 for females) was significantly smaller than that in other classes (4.59 +/- 0.12 for males and 3.90 +/- 0.13 for females) (p less than 0.01). Such a significant difference was not observed in cyclic GMP excretion. In terms of mumol/g creatinine, however, average excretion of both cyclic AMP and cyclic GMP in class A was greater than that in other classes. The amounts of urinary cyclic AMP and cyclic GMP (mumol/day) were correlated with age in the subjects from 2 to 16 years. A reverse correlation between the amounts of both nucleotides (mumol/g creatinine) and age was found in the young subjects. No correlation between the excretion of either urinary cyclic nucleotide and age was found in adults. A significantly positive correlation between cyclic AMP (mumol/day) and inorganic phosphorus (g/day) was found (r = 0.50 for males and 0.56 for females) (p less than 0.01). This correlation suggests that urinary cyclic AMP might reflect the activity of parathyroid hormone in normal humans. There was no significant correlation between cyclic GMP and electrolytes tested. The above results are considered to provide basic data for clinical evaluation of relevant disorders.

Comparison of plasma histamine and cyclic nucleotides after antigen and methacholine inhalation in man

Serial determinations of plasma histamine and cyclic nucleotides (adenosine monophosphate [AMP] and guanosine monophosphate [GMP]) were performed after inhalation of antigen and methacholine in four groups of subjects. In the first group, consisting of six antigen-sensitive subjects exhibiting bronchospasm after inhalation of ragweed or grass antigen, plasma histamine was elevated within 2 min and persisted for 30 min after inhalation of antigen. Peak histamine levels were between 18 to 80 ng/ml. In the second group, consisting of four nonatopic subjects, neither bronchospasm nor histamine was observed, despite inhalation of the same or 10-fold increased concentrations of antigen. In the third group, consisting of six subjects (three atopic and three nonatopic) exhibiting bronchospasm after inhalation of 2.5 to 10 mg of methacholine, sustained increases of histamine began at 1 min and persisted for 60 min after inhalation of methacholine. In the fourth group, seven subjects (two atopic, five nonatopic) without demonstrable bronchospasm despite inhalation of 2.5- to 10-fold increased doses of methacholine, no histamine was detected in the plasma at any time after inhalation of methacholine. Serial measurements of cyclic nucleotides showed no consistent changes in serum levels of cyclic AMP or cyclic GMP following inhalation challenge. We conclude that serum levels of histamine but not cyclic nucleotides change during bronchospasm induced by either antigen or methacholine.

Investigation of the usefulness of the plasma adenosine 3' 5' - cyclic monophosphate response to glucagon in thyroid disease

The plasma adenosine 3', 5' - cyclic monophosphate (cyclic AMP) response to 50 micrograms of intravenous glucagon was examined in 14 normal euthyroid subjects, 15 patients with thyrotoxicosis and 5 patients with myxedema. The cyclic AMP responses to 50 micrograms of intravenous glucagon was significantly higher in the hyperthyroid group than in the euthyroid or hypothyroid group. However, the areas of overlap between all three groups were large and there was little relationship between the plasma cyclic AMP response to glucagon and the biochemical assessment of thyroid function. Serial studies of the response to 50 micrograms glucagon were carried out in four patients receiving treatment for thyrotoxicosis. Again, there was not consistent relationship between the plasma cyclic AMP responsiveness to glucagon and the free thyroxine index. It is concluded that although the plasma cyclic AMP response to glucagon is increased in thyrotoxicosis and decreased in myxedema, the variability of this response in thyroid disease precludes its use as a tissue index of thyroid hormone responsiveness.

Anomalous plasma cyclic AMP responses to glucagon in patients with liver disease

The purpose of the present study is to show anomalies of the plasma cAMP response of patients with hepatic disorders to a single injection of a low dose of glucagon (1 microgram/kg body wt). The response was markedly blunted in patients with liver cirrhosis and potentiated in patients with acute or chronic hepatitis. This glucagon test is, therefore, promising for development as a simple diagnostic means without undertaking liver biopsy to distinguish cirrhosis from chronic hepatitis.

Cyclic AMP levels in blood cells from a short-cycle manic-depressive subject

Erythrocyte and leucocyte numbers and cyclic AMP content were monitored weekly in a mentally defective short-cycle manic-depressive woman. The erythrocyte count remained relatively constant but cyclic AMP content when manic was significantly higher than when depressed, and the mood and biochemical data appeared to have the same periodicity, with coincident peaks and troughs. Total leucocytes were related to mood, with peaks in the manic phase. Mononuclear cyclic AMP content varied without relation to manic or depressive phases.

The effect of hemodialysis on levels of cyclic nucleotide-associated hormones in patients with chronic renal failure

In order to determine the molecular basis for the loss of catecholamine responsiveness in skeletal muscle in chronic azotemia, plasma and serum levels of catecholamines and other hormones whose mechanisms of action are associated in part with cyclic nucleotide mediation were assessed in 37 patients with chronic azotemia. Samples were obtained prior to and immediately following conventional hemodialysis. Plasma epinephrine and norepinephrine levels in patients predialysis were increased 50% and 25% respectively compared to control subjects. Levels of insulin, prolactin, aldosterone and renin were also in creased in azotemic patients prior to dialysis. Conventional hemodialysis reduced serum levels of growth hormone, but had no effect of the elevated levels of all other hormones found in patients predialysis. In particular, plasma epinephrine and norepinephrine levels were unaffected by hemodialysis. Despite these findings, hemodialysis did reduce to normal levels the elevated plasma levels of cyclic AMP and cyclic GMP observed in uremic subjects predialysis. These data are consistent with increased adrenergic outflow in patients with chronic azotemia, and suggest a mechanism of homologous desensitization of the catecholamine receptor adenylyl cyclase unit in chronic azotemia.

Role of cyclic AMP in glucagon-induced stimulation of hepatic glucose output in man

The interrelationship between glucagon action on splanchnic glucose output and cyclic AMP production was studied in healthy volunteers after hepatic venous catheterization. Glucagon was infused according to four different protocols to achieve arterial levels ranging from 300 to 9000 ng/l. Infusion of glucagon which resulted in arterial levels of the hormone of 4000-9000 ng/l was associated with a marked increase in net splanchnic cyclic AMP production and in the arterial levels of the cyclic nucleotide. The rise in cyclic AMP efflux from the splanchnic area was transient but an augmented splanchnic production was still evident after 30 min of glucagon infusion. Splanchnic glucose output rose 3-5 fold. Infusion of glucagon at lower rates, resulting in arterial levels of 300-900 ng/l, did not measureably stimulate the efflux of cyclic AMP from the splanchnic area. In spite of this, splanchnic glucose output rose 2-3 fold and the blood glucose level increased 20-50% during glucagon infusion at these lower rates. It is concluded that (1) factors other than cyclic AMP are rate limiting in the stimulation of hepatic glucose production, and (2) although cyclic AMP is an established 'second messenger' of glucagon action, other factors may also be of importance in mediating the physiological response of this hormone.

Urinary excretion of cyclic AMP in bacterial infections

Urinary cyclic AMP excretion was found to be increased in patients with severe bacterial infections and normal renal function. The observed changes appeared due to a combination of an increased filtered load plus augmented "nephrogenous" production in some patients; while in others, only an increase in the apparent "nephrogenous" production of cAMP could be found to account for the elevation in the total urinary excretion. Since total serum calcium was found to be low in most of these patients, increased PTH secretion to reduce urinary excretion of calcium may have been responsible for an increase in renal parenchymal production, and subsequent excretion of cyclic AMP. Although speculative, this theory is tenable in that ionized hypocalcemia exists in septic patients.

Plasma catecholamines, cyclic AMP and metabolic substrates in hemorrhagic shock of the rat. The effect of adrenal demedullation and 6-OH-dopamine treatment

Plasma catecholamines, cyclic AMP and metabolic substrates in hemorrhagic shock of rats was studied in 4 groups of animals: 1) Control rats, 2) rats with adrenal demedullation, 3) rats with 6-OH-dopamine induced chemical sympathectomy, and 4) rats with combined demedullation and sympathectomy. The rats were bled to a systemic blood pressure of 35 mmHg. The basal plasma level of noradrenaline (NA), adrenaline (A) and dopamine (DA) in control animals was each about 1 nmol/1. After hemorrhage for 1 h the A levels had reached 50 nmol/l and there was little further rise after 4 h. The rise was eliminated by demedullation but unaffected by sympathectomy. NA levels rose continuously in the control and in the sympathectomized rats. At 1 h the level was about 4 nmol/l and at 4 h about 20 nmol/l. The demedullated rats showed a 3-fold increase in circulating NA, while little or no change was seen in the combined demedullated and sympathectomized rats. DA levels did not change in any of the groups during the first hour, but were markedly elevated after 4 h of hypotension. Cyclic AMP and glucose levels in plasma showed a rapid increase 1 h after hemorrhage and thereafter returned to or below basal values. Demedullation largely prevented the increase, while sympathectomy had no effect. The increase in lactate and pyruvate levels were diminished but not eliminated by either sympathectomy or demedullation. Glycerol levels were unchanged and FFA decreased in all groups of rats. The results show that the adrenal medulla is the dominating source of plasma catecholamines in hemorrhagic shock in rats. The initial increase in plasma glucose and cyclic AMP appear to be largely mediated by adrenal A. The subsequent fall in these parameters and derangement of circulatory homeostasis are not, in the present shock model, primarily due to a failure of catecholamine secretion, but rather to a decreased responsiveness of peripheral tissues to catecholamine stimulation.

Myocardial extraction of cyclic AMP during pacing-induced angina

The application of cyclic AMP as a marker of myocardial ischemia in humans with coronary artery disease has been investigated during pacing-induced angina. Cyclic AMP was determined by a radioimmunoassay. In 15 patients myocardial lactate extraction at rest (20 +/- 12%) converted to production levels (-30 +/- 23%) during angina (p less than 0.0005). Insignificant changes occurred in coronary venous plasma cyclic-AMP levels. The mean myocardial cyclic-AMP extraction at rest (0.3 +/- 8.7%) converted to small release values (-6.0 +/-11%) during angina (= n.s.). No significant correlation was found between myocardial lactate and cyclic-AMP uptake or release. Therefore, cyclic AMP is an insensitive marker in the evaluation of myocardial ischemia.

Cyclic AMP metabolism and adenylate cyclase concentration in patients with advanced hepatic cirrhosis

Glucagon was tested for its effect on plasma adenosine 3',5'-cyclic monophosphate (cyclic AMP), insulin, and glucose in healthy subjects and in patients with advanced cirrhosis of the liver. In the normal subjects, intravenous infusion of glucagon caused a significant increase in plasma cyclic AMP, glucose, and insulin. In advanced cirrhotics, plasma cyclic AMP, glucose, and insulin did not increase. Adenylate cyclase concentration was measured in liver tissue from end stage cirrhotic patients and from brain-dead organ donors whose cardiovascular function was maintained in a stable state. Basal and total adenylate cyclase concentration were not different in the two groups. Adenylate cyclase from the livers of advanced cirrhotics was, however, significantly less responsive to glucagon stimulation than was that from donor livers. Hepatocytes in advanced cirrhosis have abnormal metabolic behavior characterized by abnormal adenylate cyclase-cyclic AMP response to hormonal stimulation.

Urinary phosphate and cyclic AMP excretion following citrate-induced hypocalcemic stimulation of the neonatal parathyroid glands

Sixteen neonates, ranging in gestational age from 27 to 41 weeks and in postnatal age from birth to 8 days, were evaluated for their renal response to an endogenous PTH stimulus in 22 separate experiments. The PTH stimulus was generated by the decreased serum ionized Ca that accompanies exchange transfusion with citrated blood. The neonates increased their serum PTH from 95.8 +/- 13.1 to 133.9 +/- 15.4 microliterEq/ml (mean +/- SEM) during the transfusion, while increasing their urinary cAMP from 0.77 +/- 0.11 to 1.45 +/- 0.22 nmol/ml, and their urinary P from 12.9 +/- 2.6 to 30.6 +/- 6.1 mg/dl in the four hours following the exchange transfusion. This response was not related to postnatal or gestational age. We speculate that lack of renal responsiveness to PTH does not play a major role in the pathogenesis of early neonatal hypocalcemia.

Effect of glucagon on renin secretion in the dog

The effects of glucagon alone or in combination with theophylline on renin section were studied in relation to renal hemodynamic responses in anesthetized dogs. The intrarenal infusion of glucagon (0.5 microgram/kg/min) increased heart rate, renal blood flow, glomerular filtration rate and urine flow without any effect on renin secretion, but at a higher dose (1.0 microgram/kg/min) it increased renin secretion significantly. Theophylline (0.1 mg/kg/min) did not affect renal hemodynamics but caused a slight increase in renin secretion after 30--60 min infusion. The combined infusion of glucagon (0.5 microgram/kg/min) with theophylline (0.1 mg/kg/min) increased renin secretion markedly, although it produced renal hemodynamic changes similar to those induced by glucagon alone. These effects were not suppressed by d,l-propranolol (1.0 microgram/kg/min). It is suggested that the increase in renin secretion caused by the combined infusion of glucagon and theophylline resulted mainly from an increase in cyclic AMP in the juxtaglomerular cells, and not from stimulation of beta-adrenoceptors.

Urinary cyclic AMP in infants admitted to a neonatal intensive care unit

The urinary excretion of cyclic AMP was studied during the first 3 days of life in 46 randomly selected infants admitted to a neonatal intensive care unit. The data were compared with those of normal newborn infants. Urinary cyclic AMP concentrations were significantly correlated with gestational age (all patients), and with birth weight (all patients except infants of diabetic mothers (IDMs)). The urinary cyclic AMP/creatine ratio increased from day 1 to day 3 in normal newborns and in IDMs, and tended to increase also in small-for-gestational age (SGA), low birth weight (LBW), and sick, term infants, although the changes in the latter groups were not statistically significant. Four infants studied with parallel determinations showed increased cyclic AMP/creatinine ratio from day 1 to day 3 both in plasma and urine. All urinary cyclic AMP/creatine ratios were lower than the corresponding ratios found in plasma. In LBW infants, there was an inverse relationship between urinary cyclic AMP and serum calcium. In IDMs a positive correlation was observed between urinary cyclic AMP and blood glucose concentration. In conclusion, the excretion of cyclic AMP in sick newborn infants is influenced by the following factors: gestational age, postnatal age, birth weight, and derangements of serum calcium and blood glucose concentrations.

Plasma cyclic AMP levels during a secretin-caerulein pancreatic function test in liver and pancreatic disease

Plasma cyclic AMP levels were determined during a 40 minute secretin infusion (1 Cl.U kg-1h-1) followed by a 40 minute combined secretin (1 Cl.U kg-1h-1) caerulein (75 ng kg-1h-1) infusion. In nine healthy subjects, both secretin alone and secretin in combination with caerulein did not affect plasma cyclic AMP levels. The same was observed in six patients with chronic pancreatitis. By contrast, in patients suffering from liver disease (nine cases) or extrahepatic cholestasis (six cases), secretin elicited large increases in plasma cyclic AMP concentration; the mean values attained being, respectively, seven and four times higher than before the infusion. On the other hand, increases in plasma cyclic AMP 10 minutes after a bolus injection of glucagon (1 mg) were four times lower in the liver disease group as compared to the controls. The results reported here suggest that the liver plays a major role in the degradation of plasma cyclic AMP produced by target tissues responding to secretin, and in the release of cyclic AMP under glucagon. Liver disease reduce the capacity of the liver to clear cyclic AMP from the blood. The pancreas does not contribute significantly to the cyclic AMP in the blood.

A method for measurement of low levels of guanosine 3',5'-cylic monophosphate in blood plasma

A very sensitive method is described for the assay of guanosine 3',5'-cyclic monophosphate (cGMP) based on a competitive protein-binding technique. The procedure is simple to carry out, and does not require the purchase of expensive reagents. The binding-protein used is extracted from rat lungs and the bound and unbound cGMP are separated by ammonium sulphate precipitation. Although prior extraction of the cGMP is required, the time for this extra step is easily compensated for by the shortness of the assay time. The mean cGMP found in the blood plasma of normal young males and females is 9.9 +/- 2.4 (S.D.) nmol/l (range 5.9--14.3 nmol/l) and 9.5 +/- 2.1 (S.D.) nmol/l (range 6.9--12.7 nmol/l), respectively.

Nephrogenous cyclic adenosine monophosphate as a parathyroid function test

Nephrogenous cyclic AMP (NcAMP), total cyclic AMP excretion (UcAMP), and plasma immunoreactive parathyroid hormone (iPTH), determined with a multivalent antiserum, were prospectively measured in 55 control subjects, 57 patients with primary hyperparathyroidism (1 degrees HPT), and 10 patients with chronic hypoparathyroidism. In the group with 1 degrees HPT, NcAMP was elevated in 52 patients (91%), and similar elevations were noted in subgroups of 26 patients with mild (serum calcium </=10.7 mg/dl) or intermittent hypercalcemia, 19 patients with mild renal insufficiency (mean glomerular filtration rate, 64 ml/min), and 10 patients with moderate renal insufficiency (mean glomerular filtration rate, 43 ml/min). Plasma iPTH was increased in 41 patients (73%). The development of a parametric expression for UcAMP was found to be critically important in the clinical interpretation of results for total cAMP excretion. Because of renal impairment in a large number of patients, the absolute excretion rate of cAMP correlated poorly with the hyperparathyroid state. Expressed as a function of creatinine excretion, UcAMP was elevated in 81% of patients with 1 degrees HPT, but the nonparametric nature of the expression led to a number of interpretive difficulties. The expression of cAMP excretion as a function of glomerular filtration rate was developed on the basis of the unique features of cAMP clearance in man, and this expression, which provided elevated values in 51 (89%) of the patients with 1 degrees HPT, avoided entirely the inadequacies of alternative expressions. Results for NcAMP and UcAMP in nonazotemic and azotemic patients with hypoparathyroidism confirmed the validity of the measurements and the expressions employed.

Inhibition of plasma cyclic AMP, glucose and cortisol response to surgery by epidural analgesia

Cyclic AMP, glucose and cortisol in plasma were measured in three groups of patients undergoing hysterectomy. The operations were performed under general anaesthesia, under general anaesthesia combined with epidural analgesia and under epidural analgesia alone. Surgery elicited a significant rise in plasma cyclic AMP, glucose and cortisol when performed under general anaesthesia alone. Epidural analgesia extending from T4-6 to S5 combined with general anaesthesia abolished the rise in cyclic AMP and reduced the increase in glucose and cortisol and epidural analgesia alone extending from T4 to S5 blocked the rise in glucose and cortisol as well as that in cyclic AMP. The results support the theory that afferent nerve impulses from the area of trauma are of major importance for the catabolic state induced by surgical procedures and indicate that anaesthetic management which includes blockade of afferent nerve impulses which includes blockade of afferent nerve impulses from the area of trauma can be reduce the catabolic response to surgery. These observations could be of value in the operative management of patients with diabetes mellitus and possibly in other groups by patients with a high surgical morbidity.

Cyclic adenosine monophosphate and human gastric acid secretion

This report concerns gastric juice, plasma, and urinary levels of adenosine 3',5'-monophosphate (cAMP) in 27 subjects undergoing routine gastric analysis under maximum stimulation with betazole or pentagastrin. Cyclic AMP was measured by sensitive and specific radioimmunoassay. No increase in concentration of cAMP was noted in gastric juice, plasma, or urine following either betazole or pentagastrin stimulation. Betazole-stimulated human gastric acid secretion was associated with an increased cAMP output into the gastric juice (P less than 0.05). There was no change in cAMP output following pentagastrin stimulation. The peak acid output produced by pentagastrin and betazole was similar. The lack of increase in cAMP concentration lends support to the concept that cyclic AMP is not a primary mediator in the stimulation of gastric acid secretion by betazole or pentagastrin in the human. The physiologic significance of the increase in cAMP output following betazole stimulation remains unresolved.

Impaired responsiveness to the effect of glucagon on plasma adenosine 3':5'-cyclic monophosphate in normal man

Small doses (10-150 microgram; 3-45 nmol) of glucagon caused a dose-dependent increase in plasma adenosine 3':5'-cyclic monophosphate (cyclic AMP) concentration when injected into man. Infusion of glucagon (75 ng min-1 kg-1) for 2 h into normal subjects resulted in an initial increase in plasma cyclic AMP concentration, then a decline despite continuation of the hormone infusion and maintenance of high concentrations of circulating immunoreactive glucagon. When an injection of glucagon was given at the termination of such an infusion, the subsequent increase in plasma cyclic AMP concentration was markedly reduced when compared to that observed after a control injection which had not been preceded by a glucagon infusion. When the glucagon was injected at the end of an infusion of 1000 MRC units of bovine parathyroid hormone (BPTH) over 2 h, the plasma cyclic AMP response was normal. Conversely, after infusion of glucagon the response to injected BPTH was normal. This impairment of response was therefore specific to the hormone that had been administered and was not due to altered metabolism of circulating cyclic AMP. This phenomenon may be important in the regulation of the hormonal response by the target tissue.

Adenosine 3'5' cyclic monophosphate metabolism in patients with severe depressive illness

The daily excretion of adenosine 3'5' cyclic monophosphate (c-AMP) in a group of 19 patients with a severe depressive illness was found to be significantly decreased when compared with that from a group of euthymic patients being treated for other disorders in the same ward. The daily excretion of the depressed patients increased during the period of treatment and recovery from the illness. Treatment with a tricyclic antidepressant caused a greater increase than electroconvulsive treatment (ECT). There was no difference between the mean plasma c-AMP concentration of the depressed and euthymic groups. The mean CSF-c-AMP concentration was not different from the mean plasma c-AMP concentration in 12 patients with severe depression. There was no direct correlation between the CSF and plasma concentrations within patients. It was concluded that there may be a reversible disturbance in the renal metabolism of c-AMP in patients with severe depression.

Extracellular metabolism of cyclic AMP

Intravenously administered cyclic [8-3H]AMP to rats was quickly eliminated from the circulation. After 2 min 93% of the administered radioactivity disappeared from the plasues was recovered mainly in the form of nucleotides, ATP, ADP, AMP and IMP. In vitro contact of cyclic AMP with perfused liver, isolated liver cells and adipose tissue resulted in a rapid breakdown of the nucleotide, presumably on the outer surface of the cells. The degradation products have been identified mainly as adenosine and inosine. Incubation of adipose tissue and isolated liver cells with [3H] AMP also resulted in the breakdown of the nucleotide in themedium. The rate of AMP degradation by these tissues was faster than that for cyclic AMP degradation. The data suggest that cyclic AMP is readily metabolized on the outer surface of cells to products which may be converted within the cells to nucleotides. These findings seem of importance for the quantitative assessments of cellular cyclic AMP outflow during hormonal stimulation.

Glucagon resistance as a case of hypertriglyceridaemia

The hypothesis that glucagon resistance is a cause of hypertriglyceridaemia has been tested by studying the effects of exogenous glucagon in patients with hypertriglyceridaemia and controls. Glucagon and a greater triglyceride-lowering-effect in hypertriglyceridaemic patients than in controls. The other metabolic response to glucagon were similar in both groups. No evidence of glucagon resistance was found.

Mechanism of plasma cyclic AMP response to hypoglycemia in man

The effect of insulin-induced hypoglycemia on plasma cyclic AMP levels was studied in normal volunteers, adrenalectomized, and sympathectomized subjects. Significant increases in plasma glucagon were observed in all groups. Normal subjects all had two- to threefold rises in plasma cAMP while no response was seen in any adrenalectomized or sympathectomized subject. These findings suggest that the mechanism for enhanced plasma cAMP release during insulin-induced hypoglycemia is catecholamine dependent. Glucagon does not contribute significantly to this response.

Plasma cyclic adenosine-3', 5'-monophosphate response to glucagon in patients with liver disease

The change in plasma cyclic adenosine-3', 5'-monophosphate (AMP) was measured after intravenous injection of 1 mg of glucagon in 10 normal subjects and 30 patients with various forms of liver disease. Patients with cirrhosis and those with intrahepatic cholestasis responded normally but in patients with extrahepatic obstruction the plasma cyclic AMP response was considerably increased. Six of the eight patients with cirrhosis and a surgically created portacaval shunt had very reduced responses. This test may prove to be diagnostically important, particularly in differentiating surgical from non-surgical jaundice.

Inadequate parathyroid response in acute pancreatitis

We studied nine consecutive hypocalcemic patients with acute pancreatitis to elucidate the mechanism of hypocalcemia. Mean serum ionized calcium, 0.97 mM, was below the normal mean of 1.16 mM (P less than 0.001). Seven of eight patients tested had normal parathyroid hormone levels. All responded to parenteral parathyroid extract by increasing serum ionized calcium and urinary cyclic AMP, indicating parathyroid-hormone-responsive target organs. Calcitonin and glucagon concentrations were increased above normal in some patients, but there was no relation with serum ionized calcium. Parenteral glucagon had no significant effect on serum ionized calcium or calcitonin concentrations. These findings suggest that neither glucagon nor calcitonin was primarily responsible for the hypocalcemia, which did not produce expected increases in serum parathyroid hormone concentrations. Relative parathyroid insufficiency may account for the persistent hypocalcemia frequently observed in patients with acute pancreatitis.

Effect of intravenous glucagon on urinary catecholamine excretion in normal man

We have evaluated intravenous glucagon as pharmacologic stimulus to adrenal catecholamine secretion in normal human subjects. Urinary epinephrine and norepinephrine were measured at two hourly intervals before and after the intravenous injection of saline, 4 mg glucagon, or 0.1 mu/kg crystalline insulin. Urinary epinephrine was increased 2.3-fold over baseline after both saline and glucagon. By contrast, insulin hypoglycemia produced a 24-fold rise in urinary epinephrine. No rise in urinary norepinephrine was detected in any test. Under the conditions of this study, we conclude that epinephrine excreted after glucagon injection is due to the stress of the test itself. In normal man, glucagon either does not stimulate adrenal catecholamine secretion, or the effect is too small to measure. By contrast, in pheochromocytoma, glucagon may be specific for catecholamine secretion, based on data from the literature. In normal subjects, insulin hypoglycemia remains the only proved method for assessing adrenal catecholamine reserve.

Urinary cyclic adenosine monophosphate in young adults and elderly subjects

The 24-hour urinary excretion of cyclic 3',5'-adenosine monophosphate (cAMP) was measured by a protein-binding assay in 55 healthy volunteers (aged 20-35 yr) and in 30 hospitalized elderly subjects (aged 70-93 yr). In the older subjects the mean 24-hour cAMP excretion was significantly lower; the correlation between cAMP excretion and age demonstrated a progressive decrease from the age of 70 to the tenth decade. Many different factors could account for the reduced urinary cAMP excretion in elderly subjects: a decline in the reactivity of the adenyl cyclase-cAMP system related to physiological ageing; reduced physical activity; a reduction in the glomerular filtration rate or decreased production of cAMP by tubular cells in the senile kidney.

Effect of hypoglycemia on extracellular levels of cyclic AMP in man

This study was designed to assess the response of cyclic AMP to "endogenous" hormonal stimulation resulting from insulin-induced hypoglycemia. Insulin was administered to four normal subjects and four adrenalectomized patients. Hypoglycemia resulted in four-fold increases in plasma cyclic AMP. This response is thought to be secondary to beta-adrenergic stimulation for the following reasons: (1) the response was absent in adrenalectomized, cortisol-treated subjects; (2) it was abolished by propranolol; and (3) urinary excretion of cyclic AMP did not reflect the rise in plasma cyclic AMP.

Effect of surgical trauma on plasma concentrations of cyclic AMP and cortisol

The response of plasma cortisol and cyclic AMP concentrations to surgical trauma was examined in 7 general surgical patients. Five patients made uncomplicated recoveries and showed peak cortisol levels at 6 hours postoperatively, returning to normal by 24 hours. On patient developed postoperative pneumonia and the plasma cortisol remained elevated up to 48 hours, and the final patient showed no cortisol response at all. The plasma cyclic AMP concentrations showed a consistent rise during the operation itself, which was statistically significant when compared with preoperative levels (P less than 0.0125). Concentrations had fallen to normal by 6 hours in all the cases, except in the patient who developed pneumonia, where the plasma cyclic AMP also showed a prolonged elevation. The significance of these findings requires further elucidation, but the temporal relationship of the cyclic AMP and cortisol peaks would support the hypothesis that cyclic AMP may play a part in the mediation of ACTH release following surgical trauma.

Origin of cyclic adenosine monophosphate in saliva

The level of cyclic adenosine monophosphate (AMP) in duct saliva from the dog submandibular gland was increased after cyclic AMP was administered intravenously in vivo. Isoproterenol increased the level of cyclic AMP in plasma and saliva in vivo and in salivary gland slices in vitro, but increased the level only slightly in saliva in a prefused dog submaxillary gland.

The sources of plasma cyclic AMP: studies in the rat using isoprenaline, nicotinic acid and glucagon

The effects of intravenous administration of isoprenaline, glucagon and nicotinic acid on plasma concentrations of cyclic AMP in rats are described. In order to determine the relative importance of the liver as a source of extracellular cyclic AMP, the effects of the hormones were investigated in intact and functionally hepatectomised rats. The results showed that hepatectomy did not prevent an isoprenaline-stimulated increase in plasma cyclic AMP concentrations, although glucagon was without effect on plasma nucleotide concentrations in this group of animals. It is suggested that the liver is essential for the action of glucagon but that isoprenaline can increase plasma cyclic AMP concentrations in hepatectomised animals by increasing extrahepatic release of the nucleotide. Since inhibition of adipose tissue lipolysis with nicotinic acid did not prevent an isoprenaline or glucagon-stimulated increase in plasma cyclic AMP concentrations, adipose tissue is discounted as a major source of plasma cyclic AMP.

Urinary excretion of cyclic AMP in primary hyperparathyroidism

Urinary adenosine 3' 5' - cyclic monophosphate (cyclic AMP) was assessed by a competitive protein binding method in 19 patients with primary hyperparathyroidism (PHPT) and in 15 control subjects. The mean value of 6.6 +/- S.E. 0-64 muM per 24 hours for the patients with PHPT was higher (P less than 0-001) than the mean control value of 3-2 +/- 0-24 muM per 24 hours. In all hypercalcaemic patients without renal insufficiency, urinary cyclic AMP excretion was more than 4 muM per 24 hours and decreased in the 15 patients investigated after parathyroidectomy. In a normocalcaemic hyperparathyroid patient and in three hyperparathyroid patients with renal insufficiency, urinary cyclic AMP was less than 4 muM per 24 hours.

Pathogenic role of cyclic AMP in the impairment of urinary concentrating ability in acute hypercalcemia

A possible association between the impairment of urinary concentrating ability and an impairment of the vasopressin-dependent cyclic AMP system in hypercalcemia was investigated in rat kidneys both in vivo and in vitro. The increases of urinary osmolality and negative free water clearance and the increase of urinary cyclic AMP excretion by vasopressin injection were significantly less in the hypercalcemic rats than in the control rats. The increase of cyclic AMP concentration by vasopressin in renal medullary tissue was significantly less in the slices obtained from the hypercalcem'c rats than in those obtained from the control rats. The activation of adenylate cyclase by vasopressin was significantly less in the group with an increased concentration of calcium in media than the control group, but phosphodiesterase activity was not affected by calcium concentration in the media. These data suggest that the impaired urinary concentrating ability in hypercalcemic kidneys is due at least in part to the direct inhibitory effect of calcium on the vasopressin-dependent cyclic AMP system at the level of adenylate cyclase in renal medulla.