Non-invasive assessment of the cardiovascular eicosanoids, thromboxane A2 and prostacyclin, in randomly sampled males, with special reference to the influence of inheritance and environmental factors

1. We studied, in a random sample of 385 nonsmoking men born in 1968-1969 and 31 men born in 1913 or 1923, whether inheritance and environmental factors influenced platelet activity and vessel wall prostacyclin formation, as reflected non-invasively by the urinary excretion of the 2,3-dinor-metabolites of thromboxane A2 (2,3-dinor-thromboxane B2, Tx-M) and prostacyclin (2,3-dinor-6-keto-prostaglandin F1 alpha, PGI-M), respectively. 2. Fathers of young men with high platelet activity did not excrete more Tx-M than fathers of young men with low platelet activity. Men born in 1913 or 1923 displayed higher Tx-M (563 versus 128 pg/mg of creatinine, P less than 0.001) and PGI-M (163 versus 130 pg/mg of creatinine, P less than 0.01) excretion than those born in 1968-1969. Excretion of both Tx-M and PGI-M was correlated to the urinary output of noradrenaline and adrenaline. 3. Well-trained subjects did not differ in their excretion of Tx-M or PGI-M from those who did not exercise regularly. A recent acute infection was also unrelated to the excretion of Tx-M or PGI-M. PGI-M excretion was, however, significantly correlated to Tx-M excretion (r = 0.51, P less than 0.001). 4. This study provides the first non-invasive evidence that advancing age and sympathoadrenal tone are positively correlated to platelet activity in randomly sampled men, and that paternal inheritance, physical fitness and recent infection lack correlation to platelet activity.     

Endogenous biosynthesis of prostacyclin and thromboxane and platelet function during chronic administration of aspirin in man

To assess the pharmacologic effects of aspirin on endogenous prostacyclin and thromboxane biosynthesis, 2,3-dinor-6-keto PGF1 alpha (PGI-M) and 2,3-dinor-thromboxane B2 (Tx-M) were measured in urine by mass spectrometry during continuing administration of aspirin. To define the relationship of aspirin intake to endogenous prostacyclin biosynthesis, sequential urines were initially collected in individuals prior to, during, and subsequent to administration of aspirin. Despite inter- and intra-individual variations, PGI-M excretion was significantly reduced by aspirin. However, full mass spectral identification confirmed continuing prostacyclin biosynthesis during aspirin therapy. Recovery of prostacyclin biosynthesis was incomplete 5 d after drug administration was discontinued. To relate aspirin intake to indices of thromboxane biosynthesis and platelet function, volunteers received 20 mg aspirin daily followed by 2,600 mg aspirin daily, each dose for 7 d in sequential weeks. Increasing aspirin dosage inhibited Tx-M excretion from 70 to 98% of pretreatment control values; platelet TxB2 formation from 4.9 to 0.5% and further inhibited platelet function. An extended study was performed to relate aspirin intake to both thromboxane and prostacyclin generation over a wide range of doses. Aspirin, in the range of 20 to 325 mg/d, resulted in a dose-dependent decline in both Tx-M and PGI-M excretion. At doses of 325-2,600 mg/d Tx-M excretion ranged from 5 to 3% of control values while PGI-M remained at 37-23% of control. 3 d after the last dose of aspirin (2,600 mg/d) mean Tx-M excretion had returned to 85% of control, whereas mean PGI-M remained at 40% of predosing values. Although the platelet aggregation response (Tmax) to ADP ex vivo was inhibited during administration of the lower doses of aspirin the aggregation response returned to control values during the final two weeks of aspirin administration (1,300 and 2,600 mg aspirin/d) despite continued inhibition of thromboxane biosynthesis. These results suggest that although chronic administration of aspirin results in inhibition of endogenous thromboxane and prostacyclin biosynthesis over a wide dose range, inhibition of thromboxane biosynthesis is more selective at 20 than at 2,600 mg aspirin/d. However, despite this, inhibition of platelet function is not maximal at the lower aspirin dosage. Doses of aspirin in excess of 80 mg/d resulted in substantial inhibition of endogenous prostacyclin biosynthesis. Thus, it is unlikely that any dose of aspirin can maximally inhibit thromboxane generation without also reducing endogenous prostacyclin biosynthesis. These results also indicate that recovery of endogenous prostacyclin biosynthesis is delayed following aspirin administration and that the usual effects of aspirin on platelet function ex vivo may be obscured during chronic aspirin administration in man.     

Maintained hyperexcretion of thromboxane A2 metabolite in healthy young cigarette smokers: results from a prospective study in randomly sampled males with stable smoking habits

Summary. Although several studies have identified cigarette smoking as a factor increasing platelet formation of thromboxane A₂ (TxA₂), no prospective data on this issue have been presented in a defined population with stable smoking habits. Therefore, we analysed the relation between smoking habits and urinary excretion of the 2, 3-dinor metabolites of thromboxane A₂ (Tx-M) and prostacyclin (PGI-M) in 87 males, randomly sampled from a population of 18–19-year-old men, at two different occasions separated by 31–49 months. The daily cigarette consumption among the smokers was unchanged between the study occasions (11 vs. 11 cigarettes day^-1), but 9 of 43 initial smokers had quit. None of the initial non-smokers had begun smoking. Tx-M was higher in the smokers than in the non-smokers and correlated with the daily cigarette consumption both at the initial (176 vs. 123 pg mg^-1 creatinine; P = 0.01) and the second (214 vs. 164 pg mg^-1; P = 0.002) study occasion. Those who had quit smoking since the initial study did not differ in Tx-M from the non-smokers at the second study occasion. Urinary PGI-M did not differ between cigarette smokers, non-smokers and quitters at either of the study occasions. We conclude that cigarette smoking elicits an increased formation of thromboxane A₂, indicating platelet activation, that is stable during an observation period of up to 4 years. The increased platelet activity is reversible upon quitting.     

Formation of prostacyclin during administration of β1-selective and non-selective β-adrenergic antagonists in healthy humans

Summary. Vascular formation of prostacyclin is increased by propranolol in patients with essential hypertension. However the possible effect of β-adrenoceptor blocking drugs in healthy subjects is, however, not known. We studied this issue by analysis of the urinary excretion of the prostacyclin metabolite, 2,3-dinor-6-keto-prostaglandin F_la during intake of a (β₁-selective (metoprolol) or a non-selective (propranolol) (3-adrenoceptor antagonist. After 14 days of metoprolol treatment (100 mg d^-1) the urinary excretion of PGI-M did not differ from control (253 ± 77 vs. 220 ± 33 pg mg^-1 creatinine, respectively). Five days of randomized cross-over treatment with propranolol (80 mg day^-1) or placebo did not affect urinary PGI-M significantly either (177 ± 11 vs. 202 ± 11 pg mg^-1 creatinine, respectively). Furthermore, a daily increasing dose of propranolol (80–480 mg) progressively lowered resting blood pressure and heart rate, but failed to influence urinary excretion of PGI-M. The data demonstrate that metoprolol and propranolol do not affect basal cardiovascular formation of prostacyclin in healthy subjects. Thus, the biosynthesis of prostacyclin does not appear to be regulated by p-adrenoceptor activity under normal conditions.     

Excretion of thromboxane A2 and prostacyclin metabolites during treadmill exercise in patients with intermittent claudication

Platelet activation, with subsequent formation of thromboxane A₂ (TxA₂), is thought to play a role in the development of arterial occlusion. In patients with severe atherosclerosis of the lower limbs, characterized by leg ulcers and rest pain, the basal formation of TxA₂ and prostacyclin (PGI₂) is increased. Corresponding data in patients with more moderate atherosclerosis of the lower limbs have not been reported. Since the capacity to physical exercise is not blunted in such patients proper evaluation of their TxA₂-PGI₂ synthesis should comprise not only assessment of the basal formation, but also TxA₂/PGI₂ biosynthesis during conditions of elevated cardiovascular activity. To address this, we analysed these eicosanoids in patients with a history of intermittent claudication. Urinary dinormetabolites of TxB₂ and PGI₂ (Tx-M and PGI-M, respectively) were estimated by gas chromatography/negative ion-chemical ionization mass spectrometry in samples collected prior to, during and immediately after 20 min of severe treadmill exertion. The basal excretion of Tx-M was 105 ± 26 pg/mg creatinine. It was not changed during exercise, but increased to 176 ± 48 pg/mg creatinine (P<0·05) during the recovery. The basal excretion of PGI-M was 142 ± 25 pg/mg creatinine. The PGI-M response to exercise varied from no change at all to a 30-fold increase, without any obvious correlation to experienced leg pain, walking distance or other recorded variables. During the recovery period the outflow of PGI-M was significantly higher than at rest (482 ± 145 pg/mg creatinine; P<0·01). We conclude that in patients with intermittent claudication due to atherosclerosis (1) platelet activation does not occur during the course of the exercise, and (2) vascular prostacyclin formation can be dissociated from of TxA₂ synthesis. The observed increase in PGI-M in some of the patients is suggested to reflect tissue ischaemia induced by the lack of adequate hyperaemia during exercise.     

Endogenous prostacyclin biosynthesis and platelet function during selective inhibition of thromboxane synthase in man.

The consequences of inhibiting the metabolism of prostaglandin G2 to thromboxane A2 in man were studied by using an inhibitor of thromboxane synthase, 4-[2-(IH-imidazol-1-yl)ethoxy] benzoic acid hydrochloride (dazoxiben). Single doses of 25, 50, 100, and 200 mg of dazoxiben were administered to healthy volunteers at 2-wk intervals in a randomized, placebo-controlled, double-blind manner. Serum thromboxane B2 and aggregation studies in whole blood and platelet-rich plasma were measured before dosing and at 1, 4, 6, 8, and 24 h after dosing. Both serum thromboxane B2 and the platelet aggregation response to arachidonic acid (1.33 mM) were reversibly inhibited in a dose-dependent manner. Aggregation induced by 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (0.4 and 4.0 microM) in platelet-rich plasma as well as both aggregation and nucleotide release induced by collagen (95 micrograms/ml) in platelet-rich plasma and whole blood were unaltered by dazoxiben. Additional evidence for a platelet-inhibitory effect of the compound was a significant prolongation of the bleeding time at 1 h after administration of the highest dose (200 mg) of dazoxiben. Endogenous prostacyclin biosynthesis was assessed by measurement of the major urinary metabolite of prostacyclin, 2,3-dinor-6-keto-PGF1 alpha (PGI-M). PGI-M excretion was increased by dazoxiben; it rose a mean 2.4-fold from predosing control values at 0-6 h after administration of the highest dose studied (200 mg).     

Cigarette smoking and urinary excretion of markers for platelet/vessel wall interaction in healthy women.

1. Cigarette smoking is known to increase the risk of cardiovascular disease in both men and women. Experimental and epidemiological studies have demonstrated that cigarette smoking is associated with several indices of increased platelet activation and platelet/vessel wall interaction in men. The aim of the present study was to test the hypothesis that cigarette smoking is linked to an increased platelet activity in women also. 2. In 26 healthy smoking and non-smoking women (age 21-49 years) the urinary excretion of the thromboxane A2 metabolite 2,3-dinor-thromboxane B2 (an index of platelet activation) and of the prostacyclin metabolite 2,3-dinor-6-keto-prostaglandin F1 alpha (an index of platelet/vessel wall interaction) were analysed by g.c.-m.s. in samples collected on days 3, 10 and 20 of their respective menstrual cycles. 3. The urinary excretion of 2,3-dinor-thromboxane B2 did not vary significantly during the menstrual cycle, either in the smokers or in the non-smokers. It was consistently higher (P less than 0.004) in the group of smokers (average of day 3, 10 and 20, 395 +/- 61 pg/mg of creatinine; mean +/- SEM) than in the group of non-smokers (average 188 +/- 22 pg/mg of creatinine). 4. The urinary excretion of 2,3-dinor-6-keto-prostaglandin F1 alpha did not differ between the groups on any of the days studied (average on days 3, 10 and 20 in the smokers and non-smokers was 281 +/- 50 and 227 +/- 30 pg/mg of creatinine, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selective and nonselective inhibition of thromboxane formation

Thromboxane A2, the predominant cyclooxygenase product of arachidonic acid in the platelet, is a potent vasoconstrictor and stimulus of platelet aggregation. Prostacyclin, the principal cyclooxygenase metabolite formed in the vascular endothelium, inhibits platelet aggregation and dilates blood vessels. A therapeutic objective in the treatment of human vascular occlusive disease has been the inhibition of thromboxane formation without coincident reduction in prostacyclin biosynthesis. We compared the biochemical selectivity and platelet inhibitory actions of single doses of aspirin, a cyclooxygenase inhibitor, with imidazo(1,5-2)pyridine-5-hexanoic acid (CGS 13080), an inhibitor of thromboxane synthase. Aspirin, 325 mg, prolonged the bleeding time markedly, inhibited aggregation and nucleotide release in whole blood and platelet-rich plasma, and maximally inhibited thromboxane generation in serum. The effects of aspirin, 20 mg, were considerably less marked but, as with the higher dose, persisted throughout the study period (24 hr after dosing). CGS 13080 also prolonged bleeding time and inhibited thromboxane formation. In contrast to aspirin, these effects were reversible and inhibition of aggregation was less marked. Endogenous prostacyclin biosynthesis was measured by excretion of the major urinary metabolite 2,3-dinor-6-keto-PGF1 alpha (PGI-M). Whereas aspirin, 325 mg, reduced PGI-M excretion a mean 29%, excretion increased 48% and 100% after CGS 13080, 100 mg and 200 mg. Aspirin, 20 mg, did not alter prostacyclin biosynthesis. Inhibition of thromboxane synthase permits selective inhibition of thromboxane formation in man. Although drugs of greater potency and longer duration of action are desirable, enhanced prostacyclin synthesis may be an important component of the platelet inhibitory actions of thromboxane synthase inhibitors in man.     

Effect of regulated expression of human cyclooxygenase isoforms on eicosanoid and isoeicosanoid production in inflammation

To examine the role of cyclooxygenase (COX) isozymes in prostaglandin formation and oxidant stress in inflammation, we administered to volunteer subjects placebo or bolus injections of lipopolysaccharide (LPS), which caused a dose-dependent increase in temperature, heart rate, and plasma cortisol. LPS caused also dose-dependent elevations in urinary excretion of 2,3-dinor 6-keto PGF(1alpha) (PGI-M) and 11-dehydro thromboxane B(2) (Tx-M). Platelet COX-1 inhibition by chronic administration of low-dose aspirin before LPS did not alter the symptomatic and febrile responses to LPS, but the increment in urinary PGI-M and Tx-M were both partially depressed. Pretreatment with ibuprofen, a nonspecific COX inhibitor, attenuated the febrile and systemic response to LPS and inhibited prostanoid biosynthesis. Both celecoxib, a selective COX-2 inhibitor, and ibuprofen attenuated the pyrexial, but not the chronotropic, response to LPS. Experimental endotoxemia caused differential expression of the COX isozymes in monocytes and polymorphonuclear leucocytes ex vivo. LPS also increased urinary iPF(2alpha)-III, iPF(2alpha)-VI, and 8,12-iso-iPF(2alpha)-VI, isoprostane (iP) indices of lipid peroxidation, and none of the drugs blunted this response. These studies indicate that (a) although COX-2 predominates, both COX isozymes are induced and contribute to the prostaglandin response to LPS in humans; (b) COX activation contributes undetectably to lipid peroxidation induced by LPS; and (c) COX-2, but not COX-1, contributes to the constitutional response to LPS in humans.     

Experimental atherosclerosis: effects of oestrogen and atherosclerosis on thromboxane and prostacyclin formation

We evaluated the effect of oestrogen and experimental atherosclerosis on the in vivo formation of thromboxane and prostacyclin in rabbits. Twenty-four New Zealand White rabbits were divided into four groups. One group received control diet, one group received control diet and oestrogen, one group received control diet supplemented with 1% cholesterol and one group received cholesterol supplemented diet and oestrogen during 3 months. The in vivo formation of thromboxane and prostacyclin were measured as 2,3-dinor-TxB2 and 2,3-dinor-6-keto-PGF1 alpha in urine by gas chromatography/mass spectrometry. All rabbits on cholesterol diet became hypercholesterolaemic and developed atherosclerosis. As in previous experiments cholesterol and oestrogen-treated rabbits had only minor atherosclerosis compared to purely cholesterol-fed rabbits. The in vivo production of thromboxane in oestrogen-treated rabbits decreased from 1641 +/- 162 pg mg-1 creatinine pretreatment to 808 +/- 92 pg mg-1 creatine at 12 weeks (P = 0.0001). In contrast, the in vivo production of prostacyclin increased during oestrogen treatment (P = 0.0027). The in vivo production of prostacyclin decreased during pure cholesterol feeding without oestrogen 1384 +/- 219 pg mg-1 creatinine to 702 +/- 142 pg mg-1 creatinine (P = 0.0091). The ratio of in vivo prostacyclin to thromboxane formation increased 2-3-fold during oestrogen therapy (P = 0.0007).(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics and biochemical efficacy of pirmagrel, a thromboxane synthase inhibitor, in renal allograft recipients.

The effects of a 48-hour 0.5 mg/kg/hr infusion of the thromboxane synthase inhibitor pirmagrel were studied in 10 renal allograft recipients with cyclosporine nephrotoxicity. Plasma concentrations reached a mean steady-state plasma level of 1798 +/- 481 ng/ml. Biphasic, rapid elimination of pirmagrel was observed with a distribution half-life of 6.7 minutes and a terminal half-life of 73 minutes. Plasma clearance and the volume of distribution of the drug were 300 +/- 87 ml/hr/kg and 497 +/- 232 ml/kg, respectively. The pharmacodynamic effects of pirmagrel were marked by a mean 96% suppression of serum thromboxane B2 (TXB2), which coincided with a suppression of urinary excretion of TXB2, 2,3-dinor-TXB2, and 11-dehydro-TXB2 of 85% +/- 8%, 91% +/- 5%, and 89% +/- 9%, respectively. Urinary excretion of all thromboxane metabolites measured at the end of 1 week after termination of infusion was returned to the baseline. In conclusion, pirmagrel caused effective and sustained suppression of all thromboxane derived metabolites in plasma and urine during continuous infusion in kidney transplant patients receiving cyclosporine.     

Measurement of urinary annexin V by ELISA and its significance as a new urinary-marker of kidney disease

To confirm the significance of excretion of annexin V into the urine and the change of urinary annexin V concentration in kidney disease, a sandwich enzyme-linked immunosorbent assay (ELISA) was developed using two monoclonal antibodies. Urinary annexin V concentration was measured in healthy individuals and patients with kidney and other diseases. Urinary annexin V did not change over a range of pH between 5.0 and 8.0, and was stable during the course of the study for 24 h at room temperature and for 8 days at 4 degrees C. The mean urinary annexin V concentration in 105 normal healthy individuals was 1.5+/-1.5 ng/ml, while that in patients with nephrotic syndrome and systemic lupus erythematosis (SLE) nephritis was 9.3+/-9.1 and 6.6+/-6.7 ng/ml, respectively, and that in IgA nephropathy and chronic renal failure was 2.6+/-2.1 and 1.3+/-0.7 ng/ml, respectively. Annexin level correlated with urinary protein concentration (r=0. 717), but not the serum creatinine concentration, blood urea nitrogen (BUN) and 24-h creatinine clearance. Mean urinary annexin V concentration in patients with ischemic heart disease, hypertension, and diabetes mellitus was 1.4+/-1.0, 1.4+/-1.1, and 1.7+/-1.3 ng/ml, respectively. In one case of relapsing nephrotic syndrome, the urinary annexin V concentration was markedly increased in the early phase after admission and then decreased. This patient later required hemodialysis. These results suggest that a high urinary annexin V concentration may be an indicator of acute renal injury related to the urinary protein level.     

Decreased systemic formation of prostaglandin E and prostacyclin, and unchanged thromboxane formation, in alcoholics during withdrawal as estimated from metabolites in urine

1. The rates of secretion into the circulation of prostaglandin E, prostacyclin, and thromboxane A2 were estimated in male alcoholics on the third day of withdrawal and in control subjects by measuring appropriate metabolites in urine. 2. Urinary levels of tetranor-5,11-diketo-7 alpha-hydroxyprostane-1,16-dioic acid (the major urinary metabolite of prostaglandins E1 and E2), of 2,3-dinor-6-keto-prostaglandin F1 alpha (the major urinary metabolite of prostacyclin) and of 6-keto-prostaglandin F1 alpha (the stable hydrolysis product of prostacyclin) were significantly different from the normal subjects in the alcoholic group. In contrast, 2,3-dinor-thromboxane B2 (the major urinary metabolite of thromboxane A2) and thromboxane B2 (the stable hydrolysis product of thromboxane A2) were not significantly different between the groups. 3. These data suggest that the ratio of the vasodilator prostanoids prostaglandin E and prostacyclin and the vasoconstrictor prostanoid thromboxane A2 is lower than in normal subjects, in alcoholics during withdrawal. This may be one causal factor for the higher incidence of hypertension observed in withdrawing alcoholics compared with control subjects.     

Role of endogenous nitric oxide in circadian blood pressure regulation in healthy humans and in patients with hypertension or atherosclerosis.

BACKGROUND: Nitric oxide (NO) is involved in the regulation of blood pressure and local blood flow. Its biological activity is impaired in hypertension and atherosclerosis. Because blood pressure undergoes a circadian rhythm, we investigated whether systemic NO production is dependent on a circadian variability, and whether the phasing of diurnal rhythm in NO production corresponds to the one in blood pressure in humans. METHODS: We studied three groups of human subjects: 8 healthy volunteers (HV), 8 patients with essential hypertension (HT), and 8 patients with peripheral arterial occlusive disease (PAOD). Twenty-four-hour ambulatory blood pressure monitoring was performed simultaneously with eight consecutive 3-hour urine collection periods. Urinary nitrate excretion was measured by gas chromatography-mass spectrometry; urinary cyclic GMP excretion was assessed by RIA. RESULTS: Twenty-four-hour mean arterial blood pressure was 119.8 +/- 2.0/75.8 +/- 1.5 mm Hg in HV, 145.0 +/- 6.4/94.9 +/- 2.8 mm Hg in HT (P < 0.05 vs HV), and 137.0 +/- 7.3/81.5 +/- 1.9 mm Hg in PAOD (P = NS vs HV). There was significant circadian variation in blood pressure in all groups, but daily amplitude was lower in HT and PAOD than in HV (P < 0.05); 24-hour mean urinary nitrate excretion was 183.4 +/- 27.2 mumol/mmol creatinine in HV, 102.9 +/- 18.1 mumol/mmol creatinine in HT, and 162.1 +/- 22.2 mumol/mmol creatinine in PAOD (P < 0.05 vs HV and HT). Urinary cyclic GMP excretion was 211.8 +/- 19.0 nmol/mmol creatinine in HV, 108.6 +/- 12.4 nmol/mmol creatinine in HT, and 97.9 +/- 13.4 nmol/mmol creatinine in PAOD (P < 0.05 for HT and PAOD vs HV). Circadian variation was present in urinary nitrate and cyclic GMP excretion in HV but was significantly diminished in HT and PAOD, respectively; 24-hour mean nitrate-to-cyclic GMP ratio was 0.89 +/- 0.05 in HV and 1.10 +/- 0.10 in HT (P = NS). It was increased to 2.02 +/- 0.17 in PAOD (P < 0.05 vs HV and HT). CONCLUSIONS: There is significant circadian variation in urinary nitrate and cyclic GMP excretion rates, two marker molecules for systemic NO production, in healthy humans. NO production is increased in the morning, concomitantly with the morning increase in blood pressure, indicating that NO may buffer blood pressure increase. Diurnal variation in nitrate and cyclic GMP excretion is absent in HT, pointing to impaired NO formation. The major change in PAOD is increased nitrate/cyclic GMP ratio, which points to increased oxidative inactivation of NO in this disease. Disturbed formation and activity of NO may contribute to blood pressure alterations in cardiovascular disease.     

Assessment of the diurnal variations in urinary homovanillic and vanillylmandelic acid excretion for the diagnosis and follow-up of patients with neuroblastoma

The diurnal variation of urinary homovanillic acid (HVA) and vanillylmandelic acid (VMA) was studied in neuroblastoma patients and in a control group. Urinary HVA and VMA levels in four sequential 6-hour urine collections within a 24-hour period were compared. HVA and VMA levels were expressed in microgram/mg of urinary creatinine (UCr) and in mg/6h specimens. No statistically significant variations between the four time intervals were found when expressed in microgram/mg UCr or mg/6h. The small variations that exist in the excretion of HVA and VMA during different periods of the day are due to variations in renal excretion rather than variations in production. The results from this study indicate that a random urine sample should be as good as a 24-hour collection for diagnosis and follow-up of neural crest tumors.     

Urinary cyclic AMP and post-traumatic acute renal failure.

Consecutive daily urinary excretion of cyclic AMP has been investigated in 16 patients with severe trauma or illness, five of whom developed acute renal failure (ARF). Fluctuations in the nucleotide excretion exceeded the range found in 20 healthy volunteers (1.26-14.74, mean 7.13+/-1.18 vs. 2.04-10.10, mean 5.07+/-2.21 micronmol/24 h). This resulted in a 41% increase of cAMP excretion in the group with normal renal function (P less than 0.003) with the highest individual increase of 87%. The excretion usually reached its peak by 24 h after trauma and its lowest value by the third day, (first day vs. third day; 7.82+/-4.23 vs. 3.96+/-2.58 micronmol/24 h, P less than 0.05 for a group of 11 patients), while creatinine clearance remained normal. In four patients with severe ARF, the mean urine volume was above control value but the cAMP excretion was reduced to 3.9 to 14.4% and in one patient with a mild ARF to 60.6%. Creatinine excretion of the group was less reduced than that of cAMP (41.2% vs. 19.6%, resp.). cAMP excretion declined proportionally with diminishing creatinine clearance. In the category of 33-65 ml/min it decreased by 33.4% to 3.39 micronmol+/-1.16 micronmol/24 h. cAMP/creatinine ratio proved to be a less sensitive indicator than cAMP/24 h. Daily output of cAMP and creatinine correlated highly with diuresis in ARF patients, controls (always P less than 0.001) and less in patients with normal renal function (P less than 0.02). Urinary cAMP appears to be a very sensitive and early indicator of the onset of ARF and subsequent recovery. This warrants its further study.     

Effects of sulindac on renal and extrarenal eicosanoid synthesis

We measured the renal and extrarenal synthesis of prostacyclin and thromboxane A2, as reflected by the urinary excretion of the stable hydration products 6-keto-prostaglandin F 1 alpha and thromboxane B2 and the corresponding 2,3-dinor-derivatives, during chronic administration of sulindac (200, 400, 600, and 800 mg/day, each dose given for 7 days in successive weeks) in seven healthy subjects. Urinary eicosanoids were measured by negative ion, chemical ionization-GC/MS-validated RIA techniques. Both 2,3-dinor-thromboxane B2 and 2,3-dinor-6-keto-prostaglandin F 1 alpha showed a dose-dependent reduction, ranging between 45% and 85%. In contrast, the urinary excretion of 6-keto-prostaglandin F1 alpha and thromboxane B2 did not change significantly throughout the study. These results extend previous observations of a selective sparing of renal cyclooxygenase activity by sulindac in humans and demonstrate that this selectivity is not related to an overall weaker enzyme inhibition.     

Circadian rhythm of proteinuria in normal subjects but not in patients with glomerulonephritis

The existence of circadian variations in the urinary excretion of total protein, albumin and creatinine was investigated in subjects with normal and impaired renal function. All individuals were kept at bedrest for 24 hours. Eight consecutive urine specimens were collected every 3 hours and examined. In normal subjects the urinary total protein, albumin and creatinine excretion showed a significant increase during the 12 daytime hours compared with the night-time. The diurnal variations with peak occurrence at 13.26 h (range 09.58-16.43 h) for total protein, at 12.37 h (range 10.33-15.18 h) for albumin, at 16.33 h (range 13.22-19.24 h) for creatinine are temporally related to the ingestion of meat. In patients, by contrast, total protein, albumin and creatinine excretion in the urine were not modified significantly throughout the 24 hours period. Thus, impaired renal function is associated with the loss of the physiological circadian rhythm.     

Pharmacodynamics and Pharmacokinetics of Irbesartan in Patients With Mild to Moderate Hypertension

BACKGROUND: The pharmacodynamics (plasma angiotensin II [AII], plasma renin activity [PRA], renal function, blood pressure [BP], urinary excretion of major metabolites of prostacyclin [PGI(2)-M], and thromboxane A(2) [TXA(2)-M]) and pharmacokinetics of irbesartan were assessed in hypertensive patients. METHODS AND RESULTS: Twenty-four white patients with seated diastolic blood pressure 95 to 110 mmHg were randomized to double-blind irbesartan 300 mg or placebo once daily for 4 weeks, following a placebo lead-in. Irbesartan-treated patients had significantly greater 24-hour area under the curve values for mean change from baseline in AII and PRA versus placebo-treated patients on day B15 (AII [pg |mZ h/mL]: 261 +/- 515 vs 12 +/- 51; PRA [(ng/mL/h); h]:74 +/-162 vs -2 +/-14; P values >.05). Irbesartan significantly lowered BP without clinically important changes in renal function. Irbesartan had no effect on 24-hour urinary TXA(2)-M excretion, but significantly increased 24-hour PGI(2)-M excretion versus placebo on day B29 (20.7 +/- 23 pg/mg creatinine vs _2.3 +/- 43 pg/mg creatinine; P <.05). Pharmacokinetics were comparable to those from previous studies. The hourly relationship between plasma irbesartan concentration and antihypertensive effect indicated a broad, clockwise hysteresis, with peak concentration occurring at 1.5 hours, whereas peak antihypertensive effect occurred at 4 hours. CONCLUSIONS: Irbesartan increases plasma AII and PRA and lowers BP consistent with AT(1) receptor blockade, without clinically important effects on renal function.     

Effects of acute, heavy-resistance exercise on urinary peptide hormone excretion in humans.

To examine physical exercise-related changes in urinary excretion of protein/peptide hormones and to correlate modifications with the general increase in post-exercise proteinuria, urine C-peptide, insulin and insulin-like growth factor-I (IGF-I) and their plasma concentrations were measured. Plasma and urinary C-peptide, insulin and IGF-I before (Bex) and at the end (Eex) of physical exercise (a 2.5-hour competition, 102 km) were analysed in 20 young cyclists. At Eex compared with Bex, concentration of urinary C-peptide decreased slightly but significantly (21.3 +/- 2.7 vs. 13.5 +/- 1.7 nmol/l), but urinary insulin and urinary IGF-I concentrations significantly increased at Eex (92.5 +/- 4.2 vs. 131.4 +/- 15.7 pmol/l and 10.0 +/- 2.1 vs. 33.6 +/- 3.8 pmol/l, respectively). Plasma insulin and plasma C-peptide significantly decreased, whereas plasma IGF-I was unchanged. Urinary concentrations of total proteins and creatinine significantly increased. Both Eex urinary C-peptide/urinary protein and urinary C-peptide/urinary creatinine ratios were significantly reduced. The correlation between C-peptide and insulin in plasma was confirmed at Bex as well as Eex, but in urine only at Bex. An increased renal tubular reabsorption of C-peptide at the end of exercise might be suggested, but the expected values considering creatinine excretion were almost three times less. The Eex urinary insulin concentration was higher than expected, considering the circulation levels, but lower when compared with the expected concentration considering creatinine excretion. Physical exercise proteinuria, related to an increased protein filtration and a saturation of the mechanisms responsible for the reabsorption, does not appear similar for all peptide hormones.