Urinary Thromboxane B2 Research Articles

Effect of Thromboxane Inhibition on Renal Blood Flow in Dogs with Complete Unilateral Ureteral Obstruction

The effect of the thromboxane synthetase inhibitior OKY-046 on renal blood flow and ureteral pressure in awake dogs during 18 hours of complete unilateral ureteral obstruction was studied. OKY-046 was infused continuously throughout the period of obstruction and post-release. Renal blood flow and ureteral pressure were constantly monitored during the study. Urinary thromboxane B2 and prostaglandin E2 excretion served as markers for inhibition of renal thromboxane A2 synthesis. The triphasic relationship between ipsilateral renal blood flow and ureteral pressure previously found following unilateral ureteral obstruction was observed despite OKY-046 infusion. Inhibition of ipsilateral urinary thromboxane B2 excretion was greater than 90% compared to control while ipsilateral urinary prostaglandin E2 excretion was not consistently decreased showing specific thromboxane inhibition. These results suggest that urinary thromboxane B2 may serve as a useful marker for determining the effects of inhibition on renal thromboxane A2 production. At the level of inhibition of thromboxane synthesis achieved we did not observe any change in the late decrease in renal blood flow which is typically seen with chronic unilateral ureteral obstruction.

糖尿病患者に対するＴｈｒｏｍｂｏｘａｎｅ Ｓｙｎｔｈｅｔａｓｅ Ｉｎｈｉｂｉｔｏｒ（ＯＫＹ‐０４６）の臨床的効果

It is known that in diabetic patients with microangiopathy, the potency of blood coagulation and thromboxane production are activated. A specific thromboxane synthetase inhibitor, OKY-046 was given to 15 diabetic patients to study its effects on platelets, blood coagulation-fibrinolysis and renal function.Plasma thromboxane B2 tended to decrease after administration of OKY-046. Plasma 6-keto PGF1α indicated a significant increase after 1 month. Plasma thromboxane B2/6-keto PGF1α ratio showed a significant decrease after 2 weeks, with a gradual increase thereafter. Urinary thromboxane B2 also showed a significant decrease after 2 months. As the renal function, urinary β2-microglobulin (β2MG) showed a significant decrease after 2 months. In view of urinary β2MG and NAG levels which are said to be the early indices of nephropathy, OKY-046 was markedly effective in 3 cases, effective in 10 cases, ineffective in 2 cases and no aggravation. In view of blood β2MG which is said to reflect glomerular filtration rate, the drug was markedly effective in 2 cases, effective in 1 case and ineffective in 12 cases with no aggravation.We conclude that OKY-046 suppresses thromboxane production, activates PGI2 production and reduces thromboxane B2/6-keto PGF1α ratio in diabetic patients, suggesting to have an effect to improve diabetic nephropathy.

Functional significance of renal prostacyclin and thromboxane A2 production in patients with systemic lupus erythematosus.

We have examined the urinary excretion of stable immunoreactive eicosanoids in 23 female patients with systemic lupus erythematosus (SLE), 16 patients with chronic glomerular disease (CGD), and 20 healthy women. SLE patients had significantly higher urinary thromboxane B2 (TXB2) and prostaglandin (PG) E2 excretion and significantly lower 6-keto-PGF1 alpha than did healthy women. In contrast, CGD patients only differed from controls for having reduced 6-keto-PGF1 alpha excretion. The group of SLE patients with active renal lesions differed significantly from the group with inactive lesions for having a lower creatinine clearance and urinary 6-keto-PGF1 alpha and higher urinary TXB2. Higher urinary TXB2 excretion was associated with comparable platelet TXB2 production in whole blood, undetectable TXB2 in peripheral venous blood, and unchanged urinary excretion of 2,3-dinor-TXB2. A significant inverse correlation was found between urinary TXB2 and creatinine clearance rate (CCr). In contrast, the urinary excretion of 6-keto-PGF1 alpha showed a significant linear correlation with both CCr and para-aminohippurate clearance rate (CPAH). In four SLE and seven CGD patients, inhibition of renal cyclooxygenase activity by ibuprofen was associated with a significant reduction in urinary 6-keto-PGF1 alpha and TXB2 and in both CCr and CPAH. However, the average decrease in both clearances was 50% lower in SLE patients than in CGD patients, when fractionated by the reduction in urinary 6-keto-PGF1 alpha or PGE2 excretion. We conclude that the intrarenal synthesis of PGI2 and TXA2 is specifically altered in SLE. Such biochemical alterations are associated with changes in glomerular hemodynamics and may play a role in the progression of SLE nephropathy.

Increase in urinary thromboxane B2 in rats caused by cyclosporine.

KAWAGUCHI, AKIRA; GOLDMAN, MITCHELL H.; SHAPIRO, RON; FOEGH, MARIE L.; RAMWELL, PETER W.; LOWER, RICHARD R. Author Information

Dietary protein intake conditions the degree of renal vasoconstriction in acute renal failure caused by ureteral obstruction

Whole kidney inulin (CIn) and PAH (CPAH) clearances were measured after unilateral release of bilateral ureteral obstruction (BUO) of 24-h duration in rats fed for 4 wk isocaloric diets containing either 40% casein (high protein diet) or 6% casein (low protein diet). Values for CIn and CPAH were markedly depressed in both groups but to a greater extent in high protein-fed rats, averaging less than 60% of values measured in low protein-fed animals. Captopril, an inhibitor of the angiotensin I converting enzyme, increased CIn and CPAH markedly but comparably in high or low protein fed rats. Micropuncture studies performed after unilateral release of BUO in another group of rats fed a high or a low protein diet revealed lower levels of glomerular plasma flow rate (QA) and single nephron glomerular filtration rate (SNGFR) in rats fed a high protein diet. Values for renal arteriolar resistances were nearly twofold in high as compared with low protein-fed animals. Infusion of OKY-1581, an inhibitor of thromboxane A2 synthetase, increased both QA and SNGFR, decreased arteriolar resistances, and increased glomerular capillary ultrafiltration coefficient in high but not in low protein-fed rats. Urinary thromboxane B2 excretion per milliliter of GFR was greater in rats fed a high protein diet than in those fed a low protein diet after release of BUO but not in normal rats. In normal rats infusion of OKY-1581 did not increase CIn or CPAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Dexamethasone effect on prostanoid formation in healthy man

1. Dexamethasone was administered to six healthy female volunteers for 4 days, resulting in plasma levels of 4.8 +/- 1.4 x 10(-8) mol/l. Urinary excretions of six prostanoids as well as collagen-induced platelet thromboxane formation and aggregation were determined before, during and 1 month after administration of dexamethasone. 2. Dexamethasone had no effect on urinary thromboxane B2 (77 +/- 22 ng/day vs 63 +/- 16 ng/day during dexamethasone), dinor-thromboxane B2, the major urinary metabolite of thromboxane B2 (406 +/- 84 ng/day vs 380 +/- 90 ng/day), dinor-6-keto-prostaglandin F1 alpha, the major urinary metabolite of prostacyclin (199 +/- 41 ng/day vs 237 +/- 53 ng/day), tetranor-5,11-diketo-7 alpha-hydroxy-prostane-1,16-dioic acid, the major urinary metabolite of prostaglandins E1 and E2 (7712 +/- 1677 ng/day vs 7886 +/- 2565 ng/day) and tetranor-11-keto-5 alpha,7 alpha-dihydroxy-prostane- 1,16-dioic acid, the major urinary metabolite of prostaglandins F1 alpha and F2 alpha (14,394 +/- 2053 ng/day vs 18,288 +/- 2251 ng/day). Prostaglandin E2 excretion slightly but significantly increased from 217 +/- 48 ng/day to 294 +/- 55 ng/day. Collagen-induced platelet thromboxane formation and aggregation were not altered. 3. These results suggest that glucocorticoids do not regulate renal, platelet or total body prostanoid formation in healthy man.

Functional role of thromboxane production by acutely rejecting renal allografts in rats.

We investigated the role of thromboxane in mediating the reduction in renal function and renal blood flow characteristic of acute renal allograft rejection. We transplanted kidneys from Lewis rats to Brown-Norway recipients. By the third day after transplantation, histologic changes that were consistent with cellular rejection occurred in the kidney. These changes were associated with a moderate reduction in renal function. By day 6, histologic changes of rejection were advanced and included interstitial and perivascular infiltration by mononuclear cells. The clearances of inulin and para-aminohippuric acid were also markedly reduced. As renal function deteriorated, thromboxane B2 (TXB2) production by ex vivo perfused renal allografts increased progressively from 2 to 6 d after transplantation. However, prostaglandin (PG) E2 and 6-keto PGF1 alpha production remained essentially unchanged. There was a significant inverse correlation between the in vivo clearance of inulin and the log of ex vivo TXB2 production. Infusion of the thromboxane synthetase inhibitor UK-37248-01 into the renal artery of 3-d allografts significantly decreased urinary TXB2 excretion and significantly increased renal blood flow (RBF) and glomerular filtration rate (GFR). Although renal function improved significantly after the acute administration of UK-37248-01, GFR and RBF did not exceed 33 and 58% of native control values, respectively. In other animals, daily treatment with cyclophosphamide improved the clearances of inulin and para-aminohippuric acid and reduced thromboxane production by 6-d renal allografts. These studies demonstrate that histologic evidence of rejection is associated with increased renal thromboxane production. Inhibition of thromboxane synthetase improves renal function in 3-d allografts. Cytotoxic therapy improves renal function, reduces mononuclear cell infiltration, and decreases allograft thromboxane production. Thus, the potent vasoconstrictor thromboxane A2 may play a role in the impairment of renal function and renal blood flow during acute allograft rejection.

The effect of a thromboxane synthetase inhibitor, OKY-046, on urinary excretion of immunoreactive thromboxane B2 and 6-keto-prostaglandin F1 alpha in patients with ischemic cerebrovascular disease.

Thromboxane synthetase activity is selectively inhibited by (E)-3-[4-(1-imidazolylmethyl)phenyl]-2-propenoic acid hydrochloride monohydrate (OKY-046). A single dose of 100 mg OKY-046 was orally administered to patients with ischemic cerebrovascular disease and healthy volunteers. Platelet aggregation and thromboxane B2 (TXB2) generation of intact and homogenised platelets induced by 1.0 mM sodium arachidonate were measured before and at 1, 4, 6 and 8 h after dosing. OKY-046 inhibited arachidonate-induced aggregation in platelet rich plasma from some, but not all, individuals, whereas platelet TXB2 generation was almost completely inhibited by a single dose of 100 mg OKY-046, in all of the patients and healthy volunteers. Endogenous TXA2 and prostacyclin (PGI2) biosynthesis were assessed by measurement of urinary immunoreactive TXB2 (i-TXB2) and 6-keto-PGF1 alpha (i-6-keto-PGF1 alpha) before and at 0-3, 3-6, 6-9 h after dosing. OKY-046 increased the urinary i-6-keto-PGF1 alpha coincidently with a decrease of urinary i-TXB2, both in patients and healthy volunteers. These effects of a selective thromboxane synthetase inhibitor will improve a disturbed balance between TXA2 and PGI2, associated with the development of ischemic cerebrovascular disease.

Low plasma renin activity in diabetes. Relation to urine prostaglandin excretion.

Renal functional abnormalities, occurring before overt renal disease and possibly due to abnormal vascular control mechanisms, have been described in diabetes mellitus. We used intravenous (i.v.) furosemide, which stimulates renal prostaglandin (PG) synthesis and renin release, to compare these vasoactive systems in 14 diabetic and 23 normal control subjects. Using urine thromboxane B2 (TXB2) as an index of renal synthesis of the vasoconstrictor prostanoid TXA2, and urine 6keto-PGF1 alpha for the vasodilator PGI2, we found evidence of increased renal TXA2 synthesis in diabetic subjects in response to furosemide. The increased TXA2 synthesis did not occur at the expense of PGI2 synthesis, as urine 6keto-PGF1 alpha was not reduced. Increased TXB2 excretion in diabetic subjects was particularly marked in the first 10 min after i.v. furosemide. During this time, diabetic males excreted 31 +/- 6 ng of TXB2 compared with 10 +/- 1 ng for normal males (P less than 0.05), while diabetic females excreted 15 +/- 3 ng compared with 7 +/- 1 ng for normal females (P less than 0.05). Also, 6keto-PGF1 alpha excretion at 10 min was increased in diabetic subjects: males, 29 +/- 3 ng versus 19 +/- 3 (P less than 0.05); females, 33 +/- 8 versus 16 +/- 3 (P less than 0.05). The ratio of TXB2 to 6keto-PGF1 alpha tended to be higher in diabetic males.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased excretion of immunoreactive thromboxane B2 in cerebral ischemia.

Thromboxane B2 (TXB2) is the stable metabolite of thromboxane A2 (TXA2), a potent vasoconstrictor which induces irreversible platelet aggregation. The inhibition of TXA2 by aspirin and other agents has been associated with improved outcome following cerebral ischemia in clinical and laboratory studies. To investigate the relation of TXA2 production to cerebral ischemia, we measured the urinary excretion of TXA2 metabolites in 30 patients with acute cerebral ischemia. Urinary immunoreactive TXB2 for this group of ischemic patients was elevated compared to normals, 1818 +/- 344 pg/mg Cr (mean +/- SE) vs 880 +/- 122 pg/mg Cr (p less than .05). Among various subsets of the ischemic patients, those with severe stroke (2108 +/- 536 pg/mg Cr), large vessel disease (1646 +/- 335 pg/mg Cr), and cardiogenic stroke (2712 +/- 1045 pg/mg Cr) were all significantly elevated. Of the stroke patients, only the males demonstrated this significant elevation. These elevations of urinary immunoreactive TXB2 are consistent with a role for increased platelet activation in the pathogenesis of some forms of cerebral ischemia and suggest that gender differences in arachidonate metabolism may exist for stroke patients.

Therapeutic trial of thromboxane synthesis inhibition in the hepatorenal syndrome

Urinary excretion of the vasoconstrictor metabolite thromboxane B2 is increased in some patients with the hepatorenal syndrome. To define the role of thromboxanes in this syndrome and to evaluate a potential treatment for the renal impairment, we administered the thromboxane synthetase inhibitor dazoxiben to 5 patients with alcoholic hepatitis and rapidly progressive renal failure. Dazoxiben 200 mg/ day followed by 400 mg/day reduced urinary thromboxane B2 by ~50% without altering prostaglandin E2 or 6-keto prostaglandin F1α and without improving creatinine clearance (6 ± 2 to 6 ± 3 ml/min). In 3 additional patients, a higher dose of dazoxiben of 600 mg/day reduced thromboxane B2 by ~75% without consistent improvement in renal function. Thus, as judged by selective thromboxane inhibition with dazoxiben, thromboxanes are unlikely to be the key renal vasoconstrictor factor in the hepatorenal syndrome.

Thromboxane and prostacyclin synthesis following whole body irradiation in rats.

The effect of radiation on the mechanism and source of in vivo thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) synthesis was evaluated. Rats were irradiated with 2, 10, or 20 gray (Gy) whole-body gamma irradiation and showed an increase in urine TxB2 after either 10 or 20 Gy. Urine 6-keto-PGF1 alpha was elevated only after exposure to 20 Gy. Irradiation did not alter urine volume or osmolarity, nor was there a correlation between urine osmolarity and the urinary concentration of TxB2 r 6-keto-PGF1 alpha. Rats were pretreated with indomethacin to determine if radiation-induced alterations in urine TxB2 and 6-keto-PGF1 alpha could be suppressed. Pretreatment with indomethacin significantly decreased urine TxB2 and 6-keto-PGF1 alpha in both irradiated and nonirradiated animals. Finally, the sources of urinary cyclooxygenase products were investigated using an isogravitometric cross-perfusion system. These experiments demonstrated that urine TxB2 is derived from extrarenal sources, whereas 6-keto-PGF1 alpha is synthesized primarily by the kidney. It may be concluded that radiation exposure increases in vivo cyclooxygenase pathway activity by both renal and extrarenal tissues.

Urinary thromboxane B2 and prostaglandin E2 in the hepatorenal syndrome: Evidence for increased vasoconstrictor and decreased vasodilator factors

Vasodilatory prostaglandins function to maintain renal perfusion in patients with cirrhosis and ascites. To evaluate the potential contribution of the vasodilator prostaglandin E2 and the vasoconstrictor metabolite thromboxane B2 to the development of the hepatorenal syndrome, we measured urinary excretion of these products in 14 patients with hepatorenal syndrome and in control populations with acute or chronic liver or kidney failure. Radioimmunoassay measurements were confirmed by bioassay and by mass spectrometry. Prostaglandin E2 was decreased compared with healthy controls (2.2 ± 0.3 vs. 6.3 ± 0.8 ng/h, p < 0.01) and compared with acute renal failure (9.6 ± 2.1 ng/h) and with alcoholic hepatitis (9.2 ± 3.3 ng/h). Thromboxane B2 concentration was normal in patients with alcoholic hepatitis (0.12 ± 0.02 vs. 0.15 ± 0.03 ng/ml) and minimally increased in acute renal failure (0.18 ± 0.15 ng/ml), but markedly elevated in hepatorenal syndrome (0.69 ± 0.15 ng/ml, p < 0.001). Urinary thromboxane B2 concentration fell with improved renal function in 3 patients who survived. These data suggest an imbalance of vasodilator and vasoconstrictor metabolites of arachidonic acid in patients with the hepatorenal syndrome.

Urinary excretion of arterial blood prostaglandins and thromboxanes in man.

To determine the fraction of the arterial prostaglandin E2 (PGE2), 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 (TXB2) that is excreted unmetabolized into human urine, the 3H-labeled compounds were separately infused into the renal artery or brachial vein of 23 subjects. Urine extracts were subjected to sequential chromatography on thin-layer plates, Sephadex LH-20, and reverse-phase high-pressure liquid chromatography to isolate the unmetabolized fraction. Dual isotope ratio techniques were used to identify peak fractions, to assess purity, and to calculate recovery. Following renal artery infusions, 32.2% of 6-keto-PGF1 alpha, 13.5% of TXB2, and 3.9% of PGE2 were excreted unmetabolized. Calculated fractional excretion of these compounds on a single transit through the kidney are approximately 30, 13, and 3.9%, respectively. Following brachial vein infusion of [3H]prostaglandin I2, 2.7% of the infusate was excreted as 6-keto-PGF1 alpha, suggesting that circulating prostaglandin I2 may contribute to urinary 6-keto-PGF1 alpha. When combined with published measurements of urinary PGE2, 6-keto-PGF1 alpha, and TXB2, these data can be used to calculate the maximum arterial blood concentration of these substances. The results indicate that arterial blood concentration of PGE2, TXB2, and 6-keto-PGF1 alpha in man are only a few picograms per milliliter or less.