Thyroid hormone-induced changes in gluconeogenesis and ketogenesis in perfused rat liver.

The regulation of ketogenesis and gluconeogenesis was studied in isolated, perfused livers from hyper- and euthyroid rats. Experimental conditions were varied with respect to lactate and fatty acid concentration in the perfusion medium and with respect to the nutritional state of the rats. 1. The rate of uptake of oleate in perfused livers was independent of the thyroid and nutritional states of the animals. 2. In livers from 48-h-fasted rats no difference was found in rates of ketogenesis between the euthyroid and hyperthyroid livers except when 10 mM lactate was present in the perfusate. In recently fed rats the rates of ketogenesis from oleate (1 mM) and endogenous substrates were low in euthyroid livers (0.45 and 0.05 mumol/min per g liver, respectively), while these rates in hyperthyroid livers were (1.333 and 0.136 mumol/min per g liver, respectively). With octanoate as substrate, high rates of ketogenesis were found in recently fed livers from both euthyroid and hyperthyroid rats (1.573 and 1.717 mumol/min per g liver, respectively). 3. Without oleate in the perfusion medium the rate of gluconeogenesis from low (1 mM) lactate concentrations in livers from 48 h-fasted-rats was slightly increased in the hyperthyroid state (0.548 mumol/min per g liver) compared to the euthyroid state (0.408 mumol/min per g liver). When lactate concentration in the perfusion medium was raised to 10 mM the rate of gluconeogenesis was increased 4-fold in the hyperthyroid livers (1.800 mumol/min per g liver) but only 20% in the euthyroid livers (0.490 mumol/min per g liver). The presence of oleate (1 mM) had no effect on the rate of gluconeogenesis from low lactate concentrations in livers form 48-h-fasted animals of either thyroid state. At 10 mM lactate the inclusion of oleate caused a pronounced stimulation of gluconeogenesis in euthyroid livers (from 0.490 to 1.766 mumol/min per g liver) but not in hyperthyroid livers (from 1.800 to 1.973 mumol/min per g liver) so that the difference in the rate of gluconeogenesis between the two thyroid states disappeared. 4. The content of endogenous substrates was measured in liver biopsies taken before perfusion. The glycogen concentration was independent of the thyroid state in 48-h fasted animals. The triglyceride content was independent of the thyroid state in recently fed animals. In recently fed animals the glycogen content was reduced by 90% in hyperthyroid animals, and in 48-h-fasted animals the triglyceride content was reduced by 50% in hyperthyroid animals. 5. The energy cost of gluconeogenesis from lactate appeared to be independent of the thyroid state.

Effects of verapamil on diurnal and thyrotropin-releasing hormone-stimulated prolactin levels in man.

The effects of the calcium entry blocker verapamil on the 24-h profile of PRL secretion and on the PRL response to TRH were investigated in six healthy volunteers. Verapamil (120 mg, three times daily) was administered orally for 1 week. In all subjects both basal and TRH-stimulated PRL levels were markedly elevated by verapamil. The average diurnal PRL concentration was increased from 13.0 +/- 2.0 micrograms/L to 25.2 +/- 4.4 (mean +/- SE; P = 0.02). Diurnal rhythm and pulsatility of PRL secretion were seen both before and during verapamil administration. Mean peak PRL concentrations after TRH injection (200 micrograms, iv) were significantly increased from 72.6 +/- 11.6 to 115.2 +/- 16.8 (P less than 0.01), and the mean area under the PRL concentration-time curves from 4332 +/- 962 micrograms/L.120 min to 6975 +/- 1334 (P = 0.01). The data are in striking contrast with previous findings from in vitro studies where verapamil has been reported to block calcium-mediated stimulus-secretion coupling and inhibit hormone secretion from pituitary cells. Interference with other PRL-regulating mechanisms may account for the demonstrated verapamil-induced PRL secretion in vivo.

[Costs and prices of laboratory services]. / Laboratorieydelsers omkostninger og priser.

Cost accounting is performed in private and public laboratories. Guidelines for these activities are required and with this objective in mind, the Board of the Danish Society of Clinical Chemistry commissioned a working group to produce a position paper which is presented now in this report. The report discusses the objectives, the principles and the general requirements for cost accounting. The significance of information on costs for the clinicians' rational use of the laboratory is also illustrated. The working group points out that prerequisites for lucid and appropriate costing guidelines are clarification of which purposes information on costs are meant to serve, identification of the relevant cost centers and quality assurance of laboratory services to a defined extent. It is common practice to express laboratory costs as costs per test. The report advocates calculation of the cost per patient contact, i.e. the overall costs for laboratory service in a given investigative situation.

[Quality assurance of results of clinical chemical analyses in Danish hospital laboratories]. / Kvalitetssikring af klinisk kemiske analyseresultater på danske hospitalslaboratorier.

During the past 35 years, voluntary professional assessment of quality of the results of analyses in Danish hospital laboratories has been undertaken under the auspices of the Danish Society of Clinical Chemistry. The analytical quality of the laboratories is described by their "imprecision" and "accuracy" as expressed by "coefficient of variation" and "bias", respectively. The participation in these programmes was 90%. During the period between 1968 and 1987, inter-laboratory variation decreased markedly where all analyses were concerned. To ensure the necessary and adequate quality, establishment of specifications of quality based on clinical/biological goals of quality has proved necessary. The commonest reasons for large imprecision and bias from the target values are less specific methods of analysis, errors in calibration and sporadic "outliers". As the result of a stable organisation for ensuring quality, Denmark is well equipped for the introduction of the great demands in documentation of quality which may be anticipated from the Common Market during the immediate future.

[Ionized calcium, total calcium and albumin corrected calcium in the serum in 1213 patients with suspected calcium metabolic diseases. A prospective multicenter study]. / Ioniseret calcium, totalcalcium og albumin-korrigeret calcium i serum hos 1.213 patienter mistaenkt for calciummetabolisk sygdom. En prospektiv multicenterundersøgelse.

The correlation between serum ionized calcium, serum total calcium and albumin corrected total calcium was investigated in a prospective multicentre investigation of 1,213 patients with suspected calcium metabolic disease. 31.0% of the patients were misclassified when serum total calcium was measured instead of serum ionized calcium. The diagnostic discrepancy between the two methods decreased with the calculation of albumin corrected total calcium or calculated ionized calcium (17.9%). On justing for the analytical error connected with the measurement of ionized calcium, 11.2% of the patients were still misclassified. It is not possible precisely to predict serum ionized calcium from the measurement of serum total calcium and we recommend measurement of serum ionized calcium in patients believed to have calcium metabolic disease.

Biochemistry and differential diagnosis of metabolic acidoses.

This paper reviews the biochemical background of metabolic acidoses. The rate of development is judged from production and/or elimination rate of organic acids, particularly carboxylic acids, namely lactate, ketoacids, acetate, formate and glycollate. Further, acid production from changes in the chemical state of phosphate in tissue is evaluated. The main conclusion is that pathological conditions with acidoses are always accompanied by changes in the rate of elimination of the carboxylic acids, whereas changes in the chemical state of phosphate is of quantitatively minor importance. Further, metabolic effects of metabolic acidoses are described with special reference to the effect of low pH in the extra cellular fluid on glycolysis, gluconeogenesis, lipolysis and ketogenesis. A short outline of the differential diagnostic problems in metabolic acidoses due to changes in carbohydrate and lipid metabolism or intoxication is given.

Blood lactate and ketone body concentrations in salicylate intoxication.

Blood concentrations of lactate, ketone bodies and non-esterified (free) fatty acids were measured in 45 adult patients on admission to the poisoning treatment centre, with salicylate and mixed salicylate-sedative/ethanol poisoning. Nine patients had blood lactate concentrations above 2 mmol/l and six patients had ketone-body concentrations greater than 1 mmol/l. Eight of the nine patients with hyperlactacidaemia had mixed salicylate/ethanol or sedative poisoning, whereas four of the six patients with hyperketonaemia had pure salicylate poisoning. No direct correlation was found between the presence of these metabolic disturbances and the severity of poisoning. Since only one patient was found with organic acid concentration in the blood exceeding 5 mmol/l, it is concluded that concomitant endogenous acidosis rarely contributes to the acid-base disturbance seen in salicylate poisoning in adults.

Pathophysiology of metabolic acidosis: effect of low pH on the hepatic uptake of lactate, pyruvate and alanine.

The uptake of lactate, pyruvate and alanine in perfused rat liver was investigated under normal perfusion conditions (pH 7.4, PCO2 40 mmHg) and under conditions mimicking partially compensated metabolic acidosis (pH 6.9, PCO2 20 mmHg). At 1 mM lactate as well as 10 mM lactate in the medium a lowering of pH from 7.4 to 6.9 did not affect the lactate plus pyruvate uptake. A significant effect of the low pH was seen on pyruvate uptake which at 1 mM lactate was increased from 0.027 +/- 0.008(4) mumol/min per g liver at normal pH to 0.084 +/- 0.013(4) at low pH. At 10 mM lactate the liver produced pyruvate, but the production was significantly reduced by a lowering of the pH, being 0.45 +/- 0.13(8) mumol/min per g liver at pH 7.4 and 0.22 +/- 0.06(4) at pH 6.9. THe counterbalancing changes in lactate metabolism were too small to attain statistical significance. The stimulation of gluconeogenesis by an increase in FFA from 0 to 1 mM in the medium was unaffected by pH. Alanine uptake was decreased from 0.48 +/- 0.05(6) to 0.39 +/- 0.07(3) by lowering the pH from 7.4 to 6.9. We conclude that metabolic acidosis does not in itself inhibit the capacity of the perfused rat liver to remove lactate and pyruvate from the blood. If the same is true in man, no beneficial effect of bicarbonate treatment on lactate clearance in patients with lactic acidosis should be expected.

Lack of effect of verapamil on diurnal and thyrotropin releasing hormone stimulated thyrotropin levels in man.

We have evaluated the effects of oral administration of the calcium blocker verapamil on the pituitary secretion of TSH. Verapamil was administered 120 mg tid to 6 healthy volunteers. Plasma TSH was measured with an ultrasensitive immunoradiometric assay. TSH secretion was assessed by a 24-hour profile of unstimulated plasma concentrations and by the effect of TRH stimulation before and after 7 days of verapamil administration. No effects of verapamil was found on either basal or stimulated secretion of TSH.

Acid-base balance in diabetic ketoacidosis.

Acid-base balance during development of diabetic ketoacidosis was reappraised on the basis of old studies on urinary excretion of ions. Circulatory collapse with impaired urinary excretion of acids is a prominent feature of the late phase of diabetic ketoacidosis, in which pathophysiological measurements are difficult to make. To elucidate the balance between hepatic uptake of carboxylic acids (free fatty acids and lactate plus pyruvate) and hepatic release of carboxylic acids (ketone bodies and lactate plus pyruvate) during the late phase of diabetic ketoacidosis, perfused livers from normal and streptozotocine-diabetic rats, fasted for 48 h, were subjected to high perfusate glucose concentrations, low perfusate pH and low perfusate flow rates. Provided that flow was kept normal, there was always a net uptake of carboxylic acids. At normal flow, a low pH and a high glucose concentration in the perfusate did not affect the hepatic uptake of lactate plus pyruvate or the flux of carbon from lactate to glucose. Reduction of the perfusate flow rate by two-thirds invariably turned the liver into a state of net carboxylic acid production. The net uptake of lactate plus pyruvate was greatly reduced, mainly due to initiation of a glycolytic flux.

Development of ketonemia in fasting patients with hyperthyroidism.

Concentrations of ketone bodies, free fatty acids, glycerol, lactate, glucose, insulin, glucagon and cortisol were determined 6-hourly during 36 hours of fasting in 4 hyperthyroid patients and in 4 euthyroid controls. The concentrations of ketone bodies were elevated in hyperthyroid patients from the beginning and increased during fasting more rapidly and to higher values as compared to the controls. After 6 hours of fasting the blood ketone concentrations were 1.1--1.8 mM in hyperthyroid patients and 0.3--0.6 mM in the controls. After 36 hours the concentrations had increased to about 3.5 mM and 1.4 mM in hyperthyroid and control subjects, respectively. The concentrations of free fatty acids were identical in the groups compared postprandially, but increased significantly more in the hyperthyroid patients than in the controls during fasting. The glycerol concentration was higher in the hyperthyroid group throughout the observation period. The concentrations of insulin were slightly higher in the hyperthyroid group than in the control, whereas the concentrations of the "ketogenic" hormones, glucagon and cortisol were identical in the compared groups. It is concluded that hyperthyroidism leads to an increased tendency to ketosis, that is partly explained by increased concentrations of free fatty acids and that might also involve a direct action of long term thyroid hormone excess on enzyme activities (e.g. carnitine acyltransferase in liver).

Comparison of serum total calcium, albumin-corrected total calcium, and ionized calcium in 1213 patients with suspected calcium disorders.

The correlations between serum ionized calcium, serum total calcium, total calcium corrected for albumin and calculated ionized calcium were investigated in a prospective multicentre investigation of 1213 patients suspected of having calcium metabolic disease. Diagnostic discordance between serum total calcium and measured ionized calcium was found in 31% of the patients. With the calculation of albumin-corrected total calcium or calculated ionized calcium the discordance decreased to 17.9%. The diagnostic discordance which could be ascribed to the analytical imprecision (CV = 1.5%) amounted to only 6.7%. Although we found highly significant correlations between the parameters, a considerable scatter around the regression line made prediction of ionized calcium from albumin-corrected total calcium unreliable in many patients.