C.T. Dollery

URINARY LEUKOTRIENE E4 AFTER ANTIGEN CHALLENGE AND IN ACUTE ASTHMA AND ALLERGIC RHINITIS

The leukotrienes LTC4, D4, and E4 are potent bronchoconstrictor agents and are thought to have an important role in asthma. Urinary LTE4, a stable urinary end-product of LTC4 and LTD4, was measured, by means of high-performance liquid chromatography and radioimmunoassay. LTE4 excretion followed a log-normal distribution in twenty-nine healthy controls, with a geometric mean of 23.8 (95% confidence interval 19.9-28.2) ng/mmol creatinine. Urine was collected from eight atopic subjects for 3 h after antigen inhalation and a control urine collection was made a week later at the same time of day. Urinary LTE4 was significantly higher after antigen challenge than in the control sample (153.7 [87.1-271.3] vs 23.5 [13.7-69.5] ng/mmol creatinine; p less than 0.01). Urinary LTE4 was also measured in twenty patients with severe acute asthma and nine patients with seasonal allergic rhinitis. Mean urinary LTE4 was higher in the asthmatic patients (78.3 [46.5-131.8] ng/mmol creatinine) than in normal subjects (p less than 0.01), although there was substantial overlap into the normal range. The urinary LTE4 values of the rhinitis patients were within the normal range whether or not they had symptoms. LTC4 and LTD4 were also found in bronchoalveolar lavage fluid from one of the three atopic subjects challenged with antigen before lavage, and in a single patient who underwent lavage after admission with severe acute asthma. These studies provide evidence that leukotrienes are released in vivo in man after antigen challenge and in acute asthma.

Glucose intolerance in hypertensive patients treated with diuretics; a fourteen-year follow-up.

Abstract Glucose tolerance was studied prospectively in thirty-four hypertensive patients treated with oral thiazide diuretics without interruption for 14 years. Standard oral glucose tolerance tests were carried out before treatment and after 1, 6, and 14 years. Mean fasting blood glucose increased from 4·7±0·6 to 6·0±2·3 mmol/l and the 2 h value rose from 5·5+1·9 to 8·0±4·7 mmol/l after 14 years. Withdrawal of thiazide therapy for 7 months in ten of the patients resulted in mean reductions of 10% in fasting blood glucose and 25% in the 2 h value.

CIRCULATING PROSTACYCLIN MAY BE REDUCED IN DIABETES

remained high, iron-binding proteins were fully saturated, and his cardiomyopathy was worsening; continuous subcutaneous infusion of desferrioxamine was felt to be an appropriate treatment. With a portable syringe-pump (Mill Hill infuser, Muirhead Ltd, Beckenham, Kent) 900 mg desferrioxamine dissolved in sterile 0-154 mol/1 saline, was infused daily through a cannula (21 gauge butterfly) implanted in the s.c. tissue of the anterior abdominal wall. Over 10 days 6-61 mmol (370 mg) of iron were excreted in the urine. This is equivalent to venesecting 700-800 ml of blood. It is possible that iron removal could be increased further by using a higher dose of desferrioxamine (up to 4 g/24 h) and/or the addition of ascorbic acid.4

RELEASE OF PROSTACYCLIN IN VIVO AND ITS ROLE IN MAN

Concentrations of 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha), the stable hydrolysis product of prostacyclin (PGI2) were determined in venous blood sampled from a forearm vein after dextrose (10% w/v) perfusion and after subsequent distension with physiological saline in seven healthy volunteers. 6-oxo-PGF1 alpha was measured by gas chromatography/negative ion chemical ionisation mass spectrometry. Local release of PGI2 was demonstrated in six volunteers: in three both stimuli were effective and in three only one stimulus was effective. In seven trained athletes studied before and after vigorous exercise baseline plasma concentrations of 6-oxo-PGF1 alpha were less than 1.3-3.2 pg/ml. The concentration increased after exercise in each subject (mean 10.9 pg/ml; range 5.5-18.2 pg/ml). Mild chemical and mechanical stimuli therefore can cause local production of PGI2 from human blood vessels in vivo.

Effects of intravenous infusions of prostaglandin D2 in man

Prostaglandin D2 (PGD2) was infused intravenously into normal male volunteers. Seven subjects received infusions of 16, 32, 64 ng/kg/min and six of these a further dose of 128 ng/kg/min. Each individuals maximum dose was limited by discomfort caused by intense facial flushing and nasal congestion. At these doses there was no significant effect on systolic or diastolic blood pressure nor on spirometric measurements. There was a small but statistically significant tachycardia at 64 and 128 ng/kg/min. Collagen- and adenosine diphosphate (ADP)-induced platelet aggregation ex vivo was not affected at any of the infusion rates. Infused PGD2 is unlikely to be a useful antithrombotic agent.

Measurement of 6-oxo-PGF1α in human plasma using gas chromatography-mass spectrometry

The plasma concentration of the prostacyclin (PGI2) hydration product 6-oxo-PGF1 alpha has been assayed by stable isotope dilution GC-MS in six normal volunteers infused with increasing doses of PGI2 intravenously. The predosing levels of 6-oxo-PGF1 alpha ranged between 114 and 266 pg/ml. Infusion of PGI2 increased 6-oxo-PGF1 alpha concentration in plasma but the increments were lower than expected suggesting less conversion of the PGI2 to 6-oxo-PGF1 alpha at high infusion rates.

EFFECT OF DIURETIC THERAPY ON GLUCOSE TOLERANCE IN HYPERTENSIVE PATIENTS

Abstract Glucose-tolerance tests were done in 137 hypertensive patients before and after a year of therapy with one of four diuretics (clorexolone, ethacrynic acid, hydrochlorothiazide, or frusemide). The mean blood-sugar, serum-insulin, and serum-free-fatty-acid levels did not alter significantly during the year in the group as a whole or in the individual drug groups, except the frusemide group, where blood-sugar and serum-insulin both fell. Serum-potassium fell significantly during the year but was not related to changes in blood-sugar. 3 patients developed clinical diabetes. In 2 of these, diuretic therapy may have been of aetiological significance.

PRODUCTION OF 6-OXO-PGF1α BY HUMAN LUNG IN VIVO

The production of 6-oxo-PGF1 alpha, a stable hydrolysis product of prostacyclin (PGI2), by human lung was demonstrated in five adults. The lowest increase in 6-oxo-PGF1 alpha on passage through the lung was noted in a woman on oral contraceptives.

Cotton-wool Spots in Diabetic Retinopathy

In nineteen patients with diabetic retinopathy the appearance and life history of cotton-wool spots were studied by serial color photographs and fluorescence angiograms. Cotton-wool spots are a feature of both mild and severe diabetic retinopathy but, while their appearance is similar to that in hypertension, the associated capillary abnormalities are more severe. On fluorescence angiograms cottonwool spots are associated with arteriolar occlusion with an area of capillary closure and are surrounded by abnormal dilated capillaries. Capillary abnormalities precede the development of arteriolar occlusion which is necessary for the development of cotton-wool spots. Cotton-wool spots persist for long periods. Their mean half-life is 8.1 months in patients under forty years of age and 17.2 months in patients over the age of forty. Even when cotton-wool spots disappear, capillary closure persists. Following yttrium90 implantation of the pituitary gland the half-life of cotton-wool spots was 2.3 months.

Measurement of prostaglandin D2 and identification of metabolites in human plasma during intravenous infusion

A stable isotope dilution assay has been developed for the quantification of prostaglandin D2 (PGD2) in plasma. Samples are analysed by capillary column gas chromatography/negative ion chemical ionisation mass spectrometry (GC/NICIMS). The method employs an internal standard of [2H6]PGD2, prepared biosynthetically by incubation of rat peritoneal mast cells with deuterated arachidonic acid. No PGD2 was detected in peripheral venous plasma samples obtained from 10 healthy male volunteers (detection limit = 5 pg ml-1). Following intravenous infusion of PGD2 at increasing incremental infusion rates ranging from 16-256 ng kg-1 min-1, a dose related increase in the plasma concentration of PGD2 was observed. Plasma levels at 128 ng kg-1 min-1 ranged from 724-1444 pg ml-1. The major circulating metabolites of PGD2, during infusion, were identified as 13,14-dihydro-15-oxo-PGF2 alpha and 15-oxo-PGF2 alpha.