Engelbert Hartter

Basal and stimulated plasma levels of pancreatic amylin indicate its co-secretion with insulin in humans.

SummaryAmylin is a 37-amino acid pancreatic polypeptide, probably involved in the pathophysiology of Type 2 (non-insulin-dependent) diabetes mellitus. We have determined amylin in human plasma by extraction-based radioimmunoassay (Sep-Pak C18). Of 23 healthy control subjects plasma amylin was determined as 11.9+-3.5 ng/l. Of 27 patients with Type 2 diabetes receiving insulin the amylin levels were lower, and in 16 patients with Type 2 diabetes on oral medication they were higher than in the control subjects: 8.2+-4.4 ng/l (p<0.01) vs 18.8+-9.9 ng/l (p<0.05). In 14 Type 1 (insulin-dependent) diabetic patients we found extremely low mean amounts of amylin: 2.9+-1.9 ng/l (p<0.002). Thus, basal amylin appears to be associated with the capacity to release insulin. An oral glucose load stimulated the release of amylin, this was more pronounced in patients with Type 2 diabetes than in healthy subjects. An excellent correlation of mean amylin with mean insulin concentrations was obtained (r=0.949). In patients with Type 2 diabetes amylin was reduced congruent to a decrease in C-peptide during a hyperinsulinaemic, euglycaemic glucose clamp experiment (r=0.971 for linear correlation between C-peptide levels and amylin). We conclude, that amylin and insulin are co-secreted in humans, and that the amylin release is under feedback-control by insulin.

Plasma big endothelin-1 concentrations in congestive heart failure patients with or without systemic hypertension

Plasma endothelin concentrations were evaluated in 53 chronic, congestive heart failure (CHF) patients with or without history of systemic hypertension, as well as in 9 with hypertension only and in 22 healthy control subjects. Plasma renin, aldosterone and atrial natriuretic peptide, as well as clinical and hemodynamic data were determined. In patients with CHF, big endothelin-1 was, independent of hypertension history, significantly greater than in hypertensive patients with normal cardiac function and in control subjects (both p < 0.0001). Patients with severe CHF had significantly greater big endothelin-1 values than did those with moderate CHF. During 12-month follow-up, 11 patients with CHF underwent heart transplantation, and 9 died; these patients had significantly greater big endothelin-1 concentrations than did the 33 clinically stable patients (p < 0.001). Big endothelin-1 and atrial natriuretic peptide correlated with right atrial pressure, pulmonary capillary wedge pressure, left ventricular ejection fraction, effort capacity and severity of CHF (New York Heart Association functional class).

Decrease of stimulated amylin release precedes impairment of insulin secretion in type II diabetes

Amylin, a 37–amino acid polypeptide, has been identified as the major protein component of pancreatic amyloid deposits in patients with non-insulin-dependent (type II) diabetes mellitus. Amylin is stored and released together with insulin and has been proposed to play a major role in the pathogenesis of type II diabetes. To compare amylin release and its proportion to insulin secretion under different metabolic conditions, oral and intravenous glucose tolerance tests (OGTT and IVGTT, respectively) were performed in healthy, lean control subjects, obese patients with normal and impaired glucose tolerance (NGT and IGT, respectively), and obese type II diabetic patients. Compared with control subjects, basal and stimulated amylin secretion during OGTT was significantly higher in obese patients with NGT and IGT but not in type II diabetic patients. The integrated amylin response was significantly higher in obese patients with NGT than lean control subjects and type II diabetic patients matched for degree of obesity. The amylin-insulin ratio decreased slightly in obese subjects with NGT and IGT and significantly in type II diabetic patients. Amylin secretion was significantly stimulated during IVGTT in control subjects and obese patients with NGT and IGT but not in type II diabetic patients. These findings suggest that amylin is physiologically released by pancreatic β-cells in a constant ratio to insulin in nondiabetic subjects. Glucose-stimulated amylin secretion is increased in obese subjects with NGT and IGT. In type II diabetes mellitus, amylin secretion relative to that of insulin is decreased, and amylin is not stimulated by IVGTT.

Radioimmunoassay of endothelin.

SIR,-Dr Pritchard and colleagues (Feb 11, p 328) comment on survival in neuroblastoma being better in women than in men. Surely there are so many examples in different diseases, including several cancers, where female survival is better than that in males (let alone the fact that female babies and elderly women survive better) that this observation is unlikely to be of any special interest in neuroblastoma. Is there any condition where male survival is better? If so, this would be worth special study.

Mechanical ventilation with positive end-expiratory pressure decreases release of alpha-atrial natriuretic peptide

The influence of PEEP during controlled mechanical ventilation (CMV) on plasma levels of alpha-atrial natriuretic peptide (alpha-ANP) was examined in seven patients suffering from acute respiratory failure. The majority of patients were volume-expanded. Samples were drawn from the superior vena cava, right atrium, pulmonary artery, and radial artery. All alpha-ANP levels were significantly depressed by 15 cm H2O PEEP for one hour, when compared to CMV without PEEP. During the PEEP period, cardiac index, creatinine clearance, urinary flow and urinary sodium excretion were decreased. CMV with PEEP of 20 cm H2O depressed peripheral venous plasma levels of alpha-ANP in six volume-expanded healthy volunteers, too. The decreased release of alpha-ANP could be a consequence of atrial compression by the distended lungs and of reduced venous return. We suggest that the decline in plasma alpha-ANP levels contributes to fluid retention and renal dysfunction, which occur frequently during CMV with PEEP. More detailed studies are necessary to confirm our hypothesis.

Biosynthesis of catalase T during oxygen adaptation of Saccharomyces cerevisiae.

In recent years, the biosynthesis of mitochondrial heme proteins has been studied quite extensively in yeast and other organisms [I]. Comparatively less is known on the formation of heme proteins localized outside the mitochondria. The biosynthesis of catalase: an example of such an extramitochondrial heme protein, has been studied in rat liver by Lazarow and de Duve [2,3]. In the present investigation, such studies have been extended to Saccharomyces cerevisiae. This first report on the results of our work shows that catalase T, the major catalase protein of S. cerevisiae [4] , is formed via a heme-less and a hemecontaining precursor during oxygen adaptation of yeast grown on glucose under anaerobic conditions.

Atrial natriuretic peptide decrease during spontaneous breathing with continuous positive airway pressure in volume-expanded healthy volunteers.

We examined the effect of spontaneous breathing with continuous positive airway pressure (CPAP) on the plasma concentrations of immunoreactive (ir) alpha-atrial natriuretic peptide (ANP). In three experiments, each of 11 healthy male volunteers performed CPAP at 20, 10 and 0 cm H2O for 2 h during continuous volume loading. Samples were drawn from a peripheral vein. Plasma concentrations of irANP were determined by a sensitive radioimmunoassay. Significantly lower concentrations of irANP were observed during 20 cm H2O CPAP than at 10 and 0 cm H2O. The concentrations of irANP did not differ significantly when individuals breathing with CPAP at 10 and at 0 cm H2O were compared. Our data suggest that CPAP at 20 cm H2O lowers the release of ANP in volume-expanded subjects. We hypothesize that this phenomenon may contribute to the fluid retention and renal dysfunction observed frequently during high CPAP levels. The decline in plasma concentrations of irANP may be the result of atrial compression by the distended lungs and of reduced venous return to the heart during CPAP.

Determination of α-human atrial natriuretic peptide (α-hANP) in urine using combination of HPLC with RIA strongly indicates non-immunoreactive metabolites

Abstract Employing HPLC coupled with RIA, it was shown that α-human atrial natriuretic peptide is excreted in urine. Freshly collected urine had to be acidified to obtain reproducible results. When prepurified urine was subjected to HPLC (ion exchange and reversed phase) the subsequent quantification of α-hANP immunoreactive material in the eluate showed 10- to 30-fold greater amounts of α-hANP after treatment with HPLC; substances with the same elution parameters as synthetic α-hANP were detected, but they gave no response in the RIA.

Monoclonal antibodies to yeast catalase T

Abstract Hybridoma cell lines secreting antibodies directed against Saccharomyces cerevisiae catalase T were constructed by fusing spleen cells of mice immunized with catalase T with P3×63Ag8 mouse myeloma cells. Culture supernatants were assayed for specific antibodies by incubation with 35S-labelled yeast extracts, adsorption of the immune complexes to Protein A — carrying Staphylococus aureus cells and analysis of the adsorbed yeast proteins by sodium dodecylsulfate gel electrophoresis. Two hybrid clones were isolated mediating adsorption of a protein with electrophoretic mobility of catalase T; one of them, showing considerably higher activity, was characterized further. Anti-bodies produced by this clone belong to the IgG class of immuniglobulins; they can be used for immunoadsorption, but not for direct immunoprecipitation and recognize authentic catalase T as well as catalase T apoprotein.

RAISED CIRCULATING PLASMA LEVELS OF ATRIAL NATRIURETIC PEPTIDE IN ADOLESCENT AND ADULT PATIENTS WITH CYSTIC FIBROSIS AND PULMONARY ARTERY HYPERTENSION

Since pulmonary artery hypertension (PH) complicates advanced stages of cystic fibrosis (CF), we wondered whether plasma concentrations of h-ANP would be increased in adult patients with CF. Furthermore, if only the right ventricle is faced with an increased afterload in these patients, the increased h-ANP plasma levels should stem primarily from the right atrium. To test this hypothesis we studied 12 adult patients with CF in a clinically stable condition using right heart catheterization. Mean pressures were measured in the right atrium (Pra) and pulmonary artery (Ppa), pulmonary capillary wedge (PCWP) position, and blood were drawn from the pulmonary artery and from a peripheral vein to determine h-ANP. Plasma levels in the pulmonary artery were significantly higher than in a peripheral vein (54.3±6.0 pg/ml vs. 32.2±4.4 pg/ml; p<0.001). Four of the 12 patients had PH (Ppa, 25.8±2.9 mmHg) whereas 8 patients exhibited normal pulmonary artery pressures (Ppa, 15.9±0.7 mmHg). Patients with PH had higher Pra (4.2±0.4 mmHg) than patients with CF without PH (1.9±0.7 mmHg; p < 0.05). Plasma h-ANP concentrations were significantly higher in patients with CF with PH (70±10.4 pg/ml in the pulmonary artery; 42.6±4 pg/ml in a peripheral vein) than in patients with normal pulmonary artery pressure (43±3.3 pg/ml in the pulmonary artery; p<0.01; 24.7±5.6 pg/ml in a peripheral vein; p<0.05).Although our results are derived from a small group of patients with CF, we conclude from our results that in patients with CF PH may cause increased h-ANP secretion. The right atrium seems to be a major source.