Thromboxane inhibition and monocrotaline-induced pulmonary hypertension in rats

Monocrotaline (MCT)-induced pulmonary hypertension (PH) is a useful model for the investigation of this disorder in humans. The role of thrombocytes in the genesis of PH has already been addressed; however, the exact mechanism by which they induce PH remains to be elucidated. We investigated the effects of a thromboxane A2 (TXA2) synthase inhibitor (OKY-046) and a TXA2/prostaglandin H2 (PGH2) receptor antagonist (ONO-8809) on the development of MCT-induced PH. A single dose of MCT (60 mg/kg bodyweight; BW) was injected subcutaneously in Wistar rats 24 h after the administration of OKY-046 or ONO-8809. The TXA2 inhibitors were administered by gavage daily for 3 weeks. Urinary excretion of eicosanoids was determined by radioimmunoassay. At the end of the treatment period, the lungs, heart and kidneys were morphologically examined. The per cent medial thickness of the muscular pulmonary arteries (%MT) and the ratio of the right to the left ventricular mass including the septum (RV/LV + S) increased significantly in MCT-treated rats compared with the control rats. The %MT was attenuated by the administration of ONO-8809. Either OKY-046 or ONO-8809 attenuated the increase in RV/LV + S. In addition, both TXA2 inhibitors reduced urinary excretion of 11-dehydro-TXB2, particularly during the early phase of PH, suggesting that platelet aggregation was reduced. These findings suggest that the inhibition of TXA2 by synthase inhibition or receptor antagonism reduces or delays the development of MCT-induced PH in rats, probably by inhibiting platelet aggregation.

Effects of dietary fat saturation on eicosanoid production, platelet aggregation and blood pressure

The effects of dietary fat saturation on eicosanoid urinary excretion, platelet aggregation (PA) and blood pressure (BP) were studied in 42 healthy subjects. They consumed four consecutive diets differing in their fat saturation [saturated (SFA); monounsaturated (MUFA); polyunsaturated n-6 (PUFA n-6); and polyunsaturated n-6/n-3, (PUFA n-3)]. Each diet period lasted 5 weeks. There were no differences in 24-h 2,3-dinor-6- keto-prostaglandin F1 alpha excretion among dietary periods. A significant effect was noted regarding the excretion of 11-dehydro-thromboxane B2 (P < 0.0001). During the PUFA n-6 phase the excretion was significantly higher than during SFA and MUFA periods. Dietary fatty acid composition had a significant effect on ADP (1 mumolL-1) and collagen (2 mgL-1) induced PA. Dietary fat also had a significant effect on systolic and diastolic blood pressure (P < 0.0001). Both were significantly higher during the SFA period than during the other three periods. Our findings suggest that changes in dietary fatty acids may have mild, but significant, effects on eicosanoid production, platelet aggregation and blood pressure.

Eicosanoid excretion in hepatic cirrhosis. Predominance of 20-HETE

The cytochrome P450 system transforms AA to hydroxyeicosatetraenoic acid (HETE) metabolites that are vasoactive and affect transport in several nephron segments. A principal product of this system, 20-HETE, participates in key mechanisms that regulate the renal circulation and extracellular fluid volume. We hypothesized that excess production of 20-HETE, which constricts the renal vasculature, contributes to the renal functional disturbances in patients with hepatic cirrhosis, particularly the depression of renal hemodynamics. The development of a precise and sensitive gas chromatographic/mass spectrometric method makes it possible to measure 20-HETE and the subterminal HETEs (16-,17-,18-, and 19-HETEs) in biological fluids. As 20-HETE was excreted as the glucuronide conjugate, measurement of 20-HETE required treatment of urine with glucuronidase. We measured HETEs in the urine of patients with cirrhosis, and compared these values to those of normal subjects. Urinary excretion rate of 20-HETE was highest in patients with ascites; 12.5+/-3.2 ng/min vs. 5.0+/-1.5 and 1.6+/-0.2 ng/min in cirrhotic patients without ascites and in normal subjects, respectively. Excretion of 16-, 17-, and 18-HETEs was not increased. In patients with cirrhosis, the excretory rate of 20-HETE was several-fold higher than those of prostaglandins and thromboxane, whereas in normal subjects 20-HETE and prostaglandins were excreted at similar rates. Of the eicosanoids, only increased excretion of 20-HETE in subjects with cirrhosis was correlated (r = -0.61; P < 0.01) with reduction of renal plasma flow (RPF).

Effects of short-term exercise on female platelet function during different phases of the menstrual cycle

Previous studies have shown that premenopausal women have a low incidence of cardiovascular diseases, and that acute exercise affects male platelet function in an intensity-dependent manner. To investigate whether acute exercise affects female platelet function differently from males, sixteen sedentary women in the midfollicular phase or midluteal phase received strenuous or moderate exercise on a bicycle ergometer. Before and immediately after exercise, platelet adhesiveness, adenosine diphosphate-induced platelet aggregation and intracellular calcium concentration elevation, platelet cAMP and cGMP contents, urinary 11-dehydro-TXB2 and 6-keto-prostaglandin F1 alpha levels, and plasma nitric oxide metabolite level were determined. Our results showed no differences in exercise performance and in resting platelet function between two menstrual phases, with little change in urinary eicosanoid metabolites and platelet cAMP levels under all experimental conditions. In addition, for women in the midfollicular phase, (1) strenuous exercise increased platelet adhesiveness, adenosine-diphosphate-induced platelet aggregation, and intracellular calcium concentration elevation, whereas moderate exercise suppressed them; (2) moderate exercise enhanced plasma nitric oxide metabolite and platelet cGMP levels. In contrast, none of these platelet functions was affected by acute exercise in the midluteal phase. Therefore, we conclude that acute exercise affects female platelet function in an intensity-dependent manner in the midfollicular phase but not in the midluteal phase. The irresponsiveness of platelets to acute exercise in the luteal phase may partially explain why premenopausal women have a lower incidence of cardiovascular diseases than men.

Preventive effect of iganidipine on renal and cerebral injuries in salt-induced hypertension

Iganidipine, a new water-soluble calcium antagonist, was administered at a nonhypotensive dose (NHD) of 0.3 mg/kg/day, a moderate-hypotensive dose (MHD) of 1.0 mg/kg/day, and a sustained-hypotensive dose (SHD) of 3.0 mg/kg/day to Dahl salt-sensitive (Dahl-S) rats fed a high-salt diet for 8 weeks. The effects on survival, and on renal and cerebral injuries, were then examined. Iganidipine completely prevented hypertensive death at the SHD and tended to increase the survival at the NHD and MHD. Iganidipine reduced glomerulosclerosis and renal arterial and tubular injuries in a dose-dependent manner. Iganidipine at the SHD, but not NHD or MHD, improved plasma creatinine, serum urea nitrogen, and glomerular filtration rate. Iganidipine at all doses examined increased the urinary prostaglandin (PG) I2 and PGE2, but not PGF2alpha or thromboxane B2, and decreased plasma angiotensin II (AII) level and renin activity. The renal glomerular, tubular, and arterial injuries were significantly correlated with blood pressure (r = 0.56 to 0.80) and plasma AII level (r = 0.50 to 0.71) but not with urinary prostanoids. Iganidipine also reduced the incidence of cerebral infarction. The infarction area was slightly and significantly correlated with urinary PGI2 (r = 0.42) and PGE2 (r = 0.41) but not with blood pressure or plasma AII. In conclusion, iganidipine prevented renal and cerebral injuries in Dahl-S rats. In addition to the reduced blood pressure, the reduction of plasma AII and the increase of vasodilatory prostanoids may also partially contribute to the renal and cerebral protective effects of iganidipine.

Role of kinin and renal ANG II blockade in acute effects of ACE inhibitors in low-renin hypertension

In conscious deoxycorticosterone acetate (DOCA) salt-hypertensive dogs, the angiotensin-converting enzyme (ACE) inhibitors captopril and imidaprilat significantly decreased mean arterial pressure (MAP) and significantly increased urine flow rate, effective renal plasma flow (ERPF), glomerular filtration rate, and urinary sodium excretion. However, the angiotensin type 1 (AT1) receptor antagonist losartan caused a significant increase only in urinary sodium excretion without significant changes in MAP, urine flow rate, ERPF, and glomerular filtration rate. Simultaneous infusion of a bradykinin receptor antagonist inhibited the ACE inhibitor-induced reduction in MAP and increase in ERPF. DOCA salt treatment markedly suppressed plasma angiotensin II (ANG II) concentration (P < 0.001), although it decreased renal ANG II content only slightly (P < 0.05). Comparison of the expression of renal AT1 receptor mRNA in control kidneys with that in DOCA salt-hypertensive kidneys revealed no significant change. These results suggest that, in low-renin hypertension, inhibition of the relatively maintained ANG II production in the kidney participates in the natriuretic action of ACE inhibitors. However, hypotensive and other renal effects are mainly due to the action of bradykinin.

Thromboxane inhibition potentiates antihypertensive effects of alpha 1 adrenoceptor antagonists in the rat

We investigated the influence of the vascular and renal thromboxane system on the antihypertensive effects of the alpha 1 adrenoceptor antagonist (alpha 1 blocker) bunazosin in spontaneously hypertensive rats (SHR). SHR were treated for 2 weeks with the alpha 1, blocker bunazosin (0.5 mg/kg body weight/day). The systolic blood pressure immediately declined with bunazosin treatment, and then rose toward the level observed in untreated SHR. This antihypertensive effect was accompanied by a decrease in the ratio of prostacyclin to thromboxane A2 in the vascular wall and the kidney. A subdepressor dose of the thromboxane synthase inhibitor OKY-046 lessened the thromboxane generation during bunazosin treatment, and synergistically potentiated the antihypertensive action of the alpha 1 blocker. Such synergy was also observed between OKY-046 and prazosin, an alternative alpha 1 blocker, but not with amosulalol, an alpha 1 blocker having no quinazoline moiety. alpha 1 blockers with a quinazoline moiety dose-dependently stimulate thromboxane generation in cultured smooth muscle cells from SHR. These data indicate that alpha 1 blockers enhance thromboxane generation in the arterial wall and kidney, thereby contributing to the lessening of the antihypertensive effects observed during alpha 1 blocker treatment.

Effects of OKY-046 and nifedipine in cyclosporine-induced renal dysfunction in rats

Cyclosporine (CsA) (37.4 mumol/kg per day for 7 days) treated female Wistar rats exhibited significantly decreased creatinine clearance (Ccr) and body weight loss (BWL), but had neither proteinuria (PU) nor alteration in their urine volume (V). Light microscopic (LM) sections of rat kidneys showed that all kidneys were affected by lesions, mainly diffuse vacuolization. These changes were associated with decreased urinary excretion ratios of 6-ketoprostaglandin F1 alpha to thromboxane B2 (6kPGF1 alpha/TXB2) and prostaglandin E2 to TXB2 (PGE2/TXB2). When OKY-046, a TXA2-synthetase inhibitor or nifedipine (NFD), a calcium channel blocker and an antagonist of endotheline (ET), were administered in addition to CsA, they restored Ccr and increased urine V but they did not prevent BWL. LM sections showed that only 5 or 7 out of 9 kidneys of animals were affected, respectively. These changes were associated with prevention of the diminished ratios of urinary PGE2/TXB2 and 6kPGF1 alpha/TXB2 mainly in the OKY-046 treated animals. In conclusion, our results suggest that inhibitors of TXA2 or antagonists and/or inhibitors of endothelin play a protective role in the development of the dysfunction induced by CsA. However, the protection observed using OKY-046 and NFD did not reach that obtained by evening primrose oil (EPO) or Ketanserine (KTS), substances which prevented the fall of Ccr and BWL. Furthermore, with these protective agents only 5 out of 9 kidneys were affected and the lesions were of minor importance.

Analytical methods for the measurement of leukotrienes and other eicosanoids in biological samples from asthmatic subjects

This paper summarizes methodological aspects of measurements of eicosanoids in biological samples and describes some applications of such methods in studies on leukotriene formation in the human airways and the effects of drugs interfering with these compounds in asthmatic subjects. For estimations of in vivo production of eicosanoids, major, stable metabolites were selected for analysis in biological fluids. An enzyme immunoassay for LTE4 was validated for use in unextracted urine samples. To monitor thromboxane production, a radioimmunoassay for 11-dehydro-TXB2 was developed and used for measurements in samples of human plasma and urine. In vitro production of leukotrienes in chopped human lung was measured by UV-spectroscopy after extraction and separation on RP-HPLC. Corrections for losses during purification were performed with individually selected internal standards.

A new adenosine subtype-1 receptor antagonist, FK-838, attenuates salt-induced hypertension in Dahl salt-sensitive rats

We investigated the effects of the adenosine type-1 receptor antagonist FK-838 on salt-induced hypertension in Dahl-Sea salt-sensitive (Dahl S) rats. Dahl S rats fed a high-salt (4% NaCl) diet for 4 weeks were treated with FK-838 or hydrochlorothiazide for 4 weeks and alterations in kidney function and morphologic changes were assessed. FK-838 attenuated the development of hypertension in Dahl S rats, and caused a decrease in aortic weight in a dose dependent fashion. The adenosine antagonist did not produce any detectable metabolic disturbance. The blood pressure reduction by FK-838 was associated with attenuation of glomerular and arterial injury in the kidney. The renal protective effect of FK-838 treatment was associated with a reduction of plasma renin activity and plasma aldosterone concentration. In contrast, the thiazide diuretic, which produced almost the same blood pressure reduction as FK-838, did not attenuate renal damage. These data indicate that adenosine A1 receptor antagonism reduces salt-induced hypertension and the consequent renal injuries.

Eicosanoid excretion from the contralateral kidney in pigs with complete unilateral ureteral obstruction

PURPOSE

Eicosanoid excretion from the contralateral kidney in pigs with unilateral ureteral occlusion (UUO) was examined, and the effects of blockade of angiotensin II synthesis and cyclooxygenase inhibition were investigated.

MATERIALS AND METHODS

Urine obtained from contralateral kidneys in pigs with UUO and from the right kidney in sham-operated pigs was examined for prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) by radioimmunoassay.

RESULTS

Excretion rate of PGE2 increased from 307 +/- 69 pg. per minute to 542 +/- 149 pg. per minute (p < 0.05) during UUO. Indomethacin blocked the synthesis of both PGE2 and TxB2. Administration of an inhibitor of the angiotensin I converting enzyme resulted in a significant (p = 0.02) reduction of PGE2 excretion as well as a decrease in TxB2 excretion which was significantly lower 15 hours after UUO. Blockade of angiotensin II synthesis in the sham-operated pigs did not affect prostanoid excretion from their kidneys.

CONCLUSION

This study demonstrates that the presence of angiotensin is important for a full expression of these prostanoids in the contralateral kidney during UUO.

Urinary endothelin and renal vasoconstriction with cyclosporine or FK506 after liver transplantation

Transplant immunosuppression using either cyclosporine (CsA) or FK506 leads to renal vasoconstriction. To examine the role of endothelin (ET) in this process, we measured plasma and urinary ET before and at intervals for two years after liver transplantation. Urinary prostacyclin (as 6-keto-PG-F1 alpha), thromboxane, glomerular filtration rate and renal plasma flow were also measured. Forty-four patients were treated with CsA-based regimens and 31 patients with FK506-based regimens. Prednisone doses after one year were lower with FK506 (5.5 +/- 0.5 vs. 10.5 +/- 0.5 mg/day) by study design. Circulating plasma ET remained above normal, but not different from pre-transplant levels. Urinary ET was elevated before transplant (24.6 +/- 3.4 ng/day vs. normal 16 +/- 1.5 ng/day, P < 0.05) and rose further after transplantation (48.5 +/- 13 ng/day, P < 0.05), remaining elevated for two years. 6-keto-PG-F1 alpha fell from 2567 +/- 338 ng/day to subnormal levels and remained suppressed (1158 +/- 128 ng/day, P < 0.01). Over the same period GFR fell (84 +/- 3 ml/min to 60 +/- 3 ml/min, P < 0.01) and renal vascular resistance index rose (11,119 +/- 561 to 23,279 +/- 1692 d.s.cm-5.m-2, P < 0.01). Similar changes were observed both with CsA and FK506-based immunosuppression. No changes in ET were attributable to dihydropyridine calcium channel blockers. These results demonstrate that urinary ET changes independently from plasma ET after transplantation. Elevated ET and suppression of endothelium-derived prostacyclin persist with intense renal vasoconstriction for at least two years after transplant.

Subpressor dose of angiotensin II increases susceptibility to the haemodynamic injury of blood pressure in Dahl salt-sensitive rats

OBJECTIVE

To investigate the effects of subpressor doses of angiotensin II (Ang II) on the progression of renal injuries in Dahl salt-sensitive (Dahl-S) rats with hypertension.

METHODS

Rats were fed a high-salt (4% NaCl) diet and given an Ang II infusion (10 or 50 ng/kg per min, subcutaneously) for 4 weeks.

RESULTS

The plasma Ang II concentration achieved in the high-dose Ang II infusion was lower than that in low-salt (0.3% NaCl) normotensive rats. The Ang II infusion did not affect systolic blood pressure, cardiac hypertrophy or weight of thoracic aorta. However, the high-dose Ang II infusion increased proteinuria by 58%, enhanced the urinary N-acetyl-beta-D-glucosaminase index by 77% and reduced the glomerular filtration rate by 37%. The impaired renal function was associated with a progression of glomerulosclerotic lesions. Neither tubular nor arterial lesions were exacerbated. The infusion did not influence prostacyclin production or urinary cyclic GMP excretion.

CONCLUSION

A subpressor dose of Ang II infusion impairs renal function with progression of glomerulosclerosis, and these alterations may be due to increased susceptibility of the glomerulus in Dahl-S rats to Ang II-induced injuries. Such a mechanism might underlie a predisposition to hypertension-induced organ damage seen in Dahl-S rats with salt-induced hypertension.

Prostanoids and cyclosporin-mediated nephrotoxicity in rats: a critical appraisal

The involvement of arachidonic acid metabolism in cyclosporin (CsA) nephrotoxicity depending on CsA vehicle has been explored in this study. For this purpose creatinine clearance, urinary excretion and renal levels of eicosanoids were measured in the following rat experimental groups: group I, control; group II, CsA was administered in olive oil by gavage at 15 mg/kg/d for 7 d; group III, same as group II but 30 mg/kg/d; group IV, CsA was administered in fish oil by gavage at 15 mg/kg/d for 7 d; group V, same as group IV but 30 mg/kg/d; group VI, CsA was administered in olive oil at 15 mg/kg/d with prednisolone (1 mg/kg/d). The results indicate that (1) CsA nephrotoxicity and prostanoid alterations seem to be greatly improved when fish results indicate that (1) CsA nephrotoxicity and prostanoid alterations seem to be greatly improved when fish oil substitutes olive oil as a vehicle for CsA administration and (2) a correlation was found between eicosanoids measured and renal function, except in group II in which creatinine clearance remains unmodified but eicosanoids were altered, thus suggesting that other factors play a role in mediating nephrotoxicity due to cyclosporin.

Experimental and/or genetically controlled alterations of the renal microsomal cytochrome P450 epoxygenase induce hypertension in rats fed a high salt diet

Excess dietary salt induces a cytochrome P450 arachidonic acid epoxygenase isoform in rat kidneys (Capdevila, J. H., S. Wei, J. Yang, A. Karara, H. R. Jacobson, J. R. Falck, F. P. Guengerich, and R. N. Dubois. 1992. J. Biol. Chem. 267:21720-21726). Treatment of rats on a high salt diet with the epoxygenase inhibitor, clotrimazole, produces significant increases in mean arterial blood pressure (122 +/- 2 and 145 +/- 4 mmHg for salt and salt- and clotrimazole-treated rats, respectively). The salt- and clotrimazole-dependent hypertension is accompanied by reductions in the urinary excretion of epoxygenase metabolites and by a selective inhibition of the renal microsomal epoxygenase reaction. The prohypertensive effects of clotrimazole are readily reversed when either the salt or clotrimazole treatment is discontinued. The indication that a salt-inducible renal epoxygenase protects against hypertension, are supported by studies with the Dahl rat model of genetic salt-sensitive hypertension. Dahl resistant animals responded to excess dietary salt by inducing the activity of their kidney microsomal epoxygenase(s) (0.102 +/- 0.01 and 0.240 +/- 0.04 nmol of products formed/min per mg of microsomal protein for control and salt-treated rats, respectively). Despite severe hypertension during excess dietary salt intake (200 +/- 20 mmHg), Dahl salt-sensitive rats demonstrated no increase in renal epoxygenase activity. These studies indicate that acquired or inherited abnormalities in renal epoxygenase activities and/or regulation can be related to salt-sensitive hypertension in rodents. Studies on the human renal epoxygenase and its relationship to salt hypertension may prove useful.

Dietary stearic acid and thromboxane-prostacyclin biosynthesis in normal human subjects

Ten male subjects were fed a diet rich in stearic acid while they were contained to a metabolic ward. There were three study periods: a 20-d baseline period followed by two 40-d intervention periods. The baseline diet contained 4.4% of energy from stearic acid; one intervention diet was high in stearic acid (7.3% of energy) and the other intervention diet was low in stearic acid (1.6% of energy). The energy contribution of protein, carbohydrate, and fat (16%, 54%, and 30%, respectively) was identical for the two diets. The fat content was distributed equally among saturated, monounsaturated, and polyunsaturated fatty acids. Urinary excretions of thromboxane B2, 2,3-dinor-thromboxane B2, 6-oxo-prostaglandin F1 alpha, and 2,3-dinor-6-oxo-prostaglandin F1 alpha were not significantly different during the two different intervention periods. This suggests that changes in dietary stearic acid do not affect in vivo thromboxane A2 or prostacyclin biosynthesis.

Long-term infusion of kallikrein attenuates renal injury in Dahl salt-sensitive rats

We investigated whether long-term infusion of kallikrein would attenuate renal injury in salt-induced hypertension in Dahl salt-sensitive rats. A subdepressor dose of purified rat urinary kallikrein (700 ng/d IV) was infused by osmotic minipump for 4 weeks in male Dahl salt-sensitive rats fed a high salt (2% NaCl) diet. This dose did not affect the time-dependent elevation of blood pressure; however, urinary protein excretion was significantly decreased, and glomerular filtration rate was increased. These beneficial effects were reflected morphologically by an attenuation of glomerulosclerotic lesions and tubular injury seen in the hypertensive Dahl salt-sensitive rats. Kallikrein infusion increased urinary excretion of bradykinin and stimulated excretion of cyclic GMP, suggesting that the kallikrein-kinin-prostaglandin and nitric oxide axes were enhanced by rat urinary kallikrein infusion. The alterations induced by kallikrein infusion were potentiated by the concomitant administration of the angiotensin-converting enzyme inhibitor alacepril. These studies indicated that long-term replacement with rat tissue kallikrein attenuates renal injury in hypertensive Dahl salt-sensitive rats.

Decreased systemic thromboxane A2 biosynthesis in normal human subjects fed a salmon-rich diet

Nine normal male subjects were fed a reference diet typical of that consumed in the United States and a diet containing approximately 450 g salmon (salmon-rich diet). The salmon diet contained approximately 6 g omega 3 fatty acids that comprised 2.0% energy intake/d for each individual. The percent energy contribution of protein, carbohydrate, and fat (19%, 56%, and 25%, respectively) was identical for the two diets. Urinary excretion of 2,3-dinor-thromboxane B2 was significantly lower (0.74 +/- 0.26 ng/24 h) with the salmon diet compared with the reference diet (0.95 +/- 0.31 ng/24 h). In addition, in vitro generation of thromboxane B2 in response to collagen-stimulated aggregation of platelet-rich plasma from subjects consuming the salmon diet was reduced (1.87 +/- 0.79 ng/mL) compared with subjects consuming the reference diet (3.10 +/- 1.81 ng/mL). Urinary 2,3-dinor-6-oxo-prostaglandin F1 alpha excretion in subjects was not significantly different between the salmon diet (0.69 +/- 0.33 ng/24 h) and the reference diet (0.81 +/- 0.44 ng/24 h).

Inflammatory mediator profile in urine and bladder wash fluid of patients with interstitial cystitis

Interstitial cystitis is a syndrome of urinary urgency, frequency and suprapubic pain. We investigated the role of inflammatory mediators in 96 patients with histories and symptoms consistent with interstitial cystitis, and 13 controls from The New York Hospital-Cornell Medical Center, University of Washington and University of California at San Diego. Patients were classified into either group A (meets all criteria of the National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases for inclusion in research studies), group B (meets all of these criteria but without glomerulations) or an "other" group. A small number of group A patients had detectable interleukin-6 in the urine. Urinary concentrations of tumor necrosis factor, prostaglandins E2, D2 and F2 alpha, and thromboxane B2 were not different among either patient groups or controls. Urine specimens contained inhibitors of the bioactivity of interleukin-6 and tumor necrosis factors but no differences between patients or controls were found. No factors chemotactic for human neutrophils were detected in a small patient sample. Bladder wash fluid concentrations of prostaglandins E2, D2 and F2 alpha, and thromboxane were much lower than urinary levels. Bladder wash fluid interleukin-6 and tumor necrosis factor were not detectable. The results suggest that while a small subset of patients may have elevated levels of interleukin-6 the majority of patients do not appear to have elevated levels of inflammatory mediators in the urine or bladder wash fluid. Evaluation of patient bladder tissue may indicate changes not detectable in urine or bladder wash fluid. Alternatively, other etiologies must be considered in those patients.

Inhibitory effect of UK,74505, a potent and specific oral platelet activating factor (PAF) receptor antagonist, on airway and systemic responses to inhaled PAF in humans

Inhaled PAF provokes bronchoconstriction, causes peripheral blood neutropenia with rebound neutrophilia, and generates urinary production of the bronchoconstrictor eicosanoids, thromboxane (TX)A2, and the cysteinyl leukotrienes. We examined the effects of an oral PAF antagonist UK,74505 on each of these responses to a single 36 micrograms dose of inhaled PAF. In a double-blind randomized placebo-controlled crossover study, 12 normal male subjects inhaled PAF on two consecutive days, 3 and 24 h after intake of two doses of UK,74505 25 mg and 100 mg, or matched placebo (P). After P, inhalation of PAF provoked bronchoconstriction, measured at regular time points for 60 min as a change in sGaw from baseline and computed as area under the curve (AUC), induced a neutropenia at 5 min and rebound neutrophilia at 2 h, and stimulated production of urinary eicosanoids. Bronchoconstriction was maximal at 5 min but had receded at 1 h; (AUC mean [95% Cl]; 20.0 [13.2, 26.8] at 3 h; 11.0 [5.3, 16.6] at 24 h) and was completely abolished by both doses of UK,74505 at 3 h and by the higher 100 mg dose at 24 h. PAF-induced neutropenia and rebound neutrophilia were abolished by both doses of drug; neutropenia at 5 min (expressed as mean [95% Cl] change from baseline; -2.5 x 10(9)/L [-2.9, -2.1] after P; -0.3 [-0.7, 0.1] after 25 mg; 0.1 [-0.3, 0.4] after 100 mg), neutrophilia at 2 h (2.0 [-1.3, 2.6] after P; -0.2 [-0.8, 0.5] after 25 mg; -0.1 [-0.8, 0.5] after 100 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Antiphospholipid antibodies enhance thrombin-induced platelet activation and thromboxane formation

In a group of 6 patients with lupus anticoagulant (LA) and antiphospholipid (aPL) antibodies detected by ELISA overnight urine and blood were simultaneously collected. A significantly increased urinary excretion of the platelet-derived thromboxane (TX) metabolite 11-dehydro-TXB2 was found in this group, as compared to 12 healthy individuals. In contrast, a small but significant reduction of the vascular prostacyclin (PGI2) metabolite 2,3-dinor-6-keto-prostaglandin F1 alpha was observed. To further elucidate the effect of these antibodies on platelet activation we isolated the F(ab')2 fragments from IgG of the 6 patients and 5 controls, and we evaluated the effect of these fragments on the responses of isolated normal platelets to thrombin. Patients' F(ab')2 increased platelet aggregation and serotonin release of platelets stimulated by low dose thrombin (0.01 U/ml). At threshold thrombin concentration (0.05 U/ml) an enhanced TXB2 production was also observed. In summary, our results show, in addition to the altered TXA2/PGI2 balance observed in vivo, a direct stimulatory effect of aPL antibodies on platelet activation in vitro. This effect is related to recognition of phospholipid epitopes on platelets as shown by its neutralization upon preincubation with phospholipids. This phenomenon may be relevant for the thrombotic tendency of these patients.

Nicotine effects on eicosanoid formation and hemostatic function: comparison of transdermal nicotine and cigarette smoking

OBJECTIVES

The purpose of this study was to examine the possible role of nicotine in enhancing coagulation and to assess the potential cardiovascular toxicity of transdermal nicotine therapy for smoking cessation.

BACKGROUND

Cigarette smoking increases the risks of acute coronary events. A likely contributing mechanism is activation of coagulation. The role of nicotine in enhancing coagulability has not been resolved.

METHODS

We compared in a crossover study the effects of cigarette smoking, transdermal nicotine and placebo transdermal nicotine, each for 5 days, in 12 healthy smokers.

RESULTS

Cigarette smoking increased the urinary excretion of 11-dehydro-thromboxane B2 (reflecting thromboxane A2 generation) and increased plasma concentration of the platelet alpha-granule constituents, platelet factor 4 and beta-thromboglobulin, compared with placebo treatment, indicating in vivo platelet activation. Cigarette smoking was also associated with higher levels of fibrinogen in plasma. Transdermal nicotine produced plasma levels of nicotine in the same range as those during smoking but had no effect on thromboxane A2 metabolite excretion, platelet alpha-granule release or plasma fibrinogen, compared with placebo. Excretion of 2,3-dinor-6-keto-PGF1 alpha (reflecting prostacyclin generation) was not significantly influenced by any treatment. These results suggest that nicotine as such is not responsible for the platelet activation or elevation of plasma fibrinogen seen in smokers. However, we cannot exclude the possibility that intermittent bolus-like dosing of nicotine from cigarettes could have different effects from those produced by continually released transdermal nicotine. Other findings were that cigarette smoking and transdermal nicotine treatment were both associated with a higher white blood cell count compared with the placebo patch condition, suggesting a direct effect of nicotine to increase circulating white cells. Factor VII coagulant activity (VIIc) was significantly lower during cigarette smoking, than during either nicotine or placebo patch conditions.

CONCLUSIONS

Transdermal nicotine has less effect on platelet activation and catecholamine release than does cigarette smoking, and its use in smoking cessation treatment of patients with coronary heart disease is likely to be safer than cigarette smoking.

Thromboxane A2 receptor antagonism and synthase inhibition in essential hypertension

Short-term effects of ridogrel, a combined thromboxane synthase inhibitor and receptor antagonist, were investigated in 16 patients with uncomplicated essential hypertension. After a 2-week placebo period without antihypertensive medication, patients were admitted to the hospital overnight on two occasions 3 weeks apart. On each occasion, they received two doses of either placebo or ridogrel (300 mg) 12 hours apart according to a double-blind crossover protocol. Renal and systemic thromboxane A2 and prostacyclin biosynthesis were investigated by measuring urinary excretion of thromboxane B2, 6-oxo-prostaglandin F1 alpha, and their respective 2,3-dinor metabolites using gas chromatography/mass spectrometry. Responses of platelets to a thromboxane A2 mimetic and to adenosine diphosphate were studied turbidometrically. Blood pressure was measured automatically at 20-minute intervals. Ridogrel reduced excretion of 2,3-dinor-thromboxane B2 and thromboxane B2 compared with placebo (21 +/- 6 versus 279 +/- 28 and 14 +/- 4 versus 39 +/- 9 ng/g creatinine, respectively; P < .0001 and P < .05). Excretion of 2,3-dinor-6-oxoprostaglandin F1 alpha and 6-oxoprostaglandin F1 alpha was increased by ridogrel compared with placebo (184 +/- 20 versus 146 +/- 11 and 86 +/- 9 versus 58 +/- 6 ng/g creatinine, respectively; P < .05). Ridogrel selectively antagonized platelet aggregation to the thromboxane mimetic (P < .0001). Blood pressure did not differ significantly between ridogrel and placebo treatment periods. Thus, in patients with essential hypertension, acute administration of ridogrel reduces renal and extrarenal thromboxane A2 biosynthesis, increases renal and extrarenal prostacyclin biosynthesis, inhibits thromboxane receptor-activated platelet aggregation, but has no effect on systemic arterial pressure.

Regulation of renin-angiotensin system in unilateral ureteral obstruction

The effect of 24-hour unilateral ureteral obstruction (UUO) on the expression and regulation of the renin-angiotensin system (RAS) in rats and of pretreatment with lisinopril (5 mg/kg/day) or the AT1-R inhibitor, losartan, (10 mg/kg/day) on renal hemodynamics was evaluated. Both drugs improved the post-obstructed kidney (POK) renal hemodynamics, lowered MAP, and normalized eicosanoid excretion by the POK. Cortex and medulla POK:CK ratio of relative density R mRNA was approximately 3.5 for both. Sham, POK, and CK showed renin immunoreactivity and R mRNA exclusively in juxtaglomerular position. In addition, in POK renin was expressed in mesangial cells, along greater lengths of afferent arterioles and in dilated distal tubules and loops of Henle. In situ hybridization revealed that approximately 20% more glomeruli in POK than CK overexpressed R mRNA. Blood vessels of POK consistently showed greater ACE and Ao mRNA expression than CK. Overexpression of the genes coding for members of the RAS is possibly responsible for local Ang II production which, in view of the response to CEI and AT1-R inhibitors, is at least partly responsible for the severe hemodynamic changes in UUO.

Dietary modification of omega 6 fatty acid intake and its effect on urinary eicosanoid excretion

A group of women were fed two separate diets in a crossover study and urinary eicosanoids were quantified. One diet contained 3.1% of total energy (en%) as polyunsaturated fatty acids (3.0 en% linoleic acid) and the other contained 8.4 en% polyunsaturated fatty acids (8.3 en% linoleic acid). Carbohydrate replaced fat in the low-polyunsaturated-fat diet. No changes were observed in the urinary excretion of 6-oxo-prostaglandin F1 alpha, its 2,3-dinor metabolite or thromboxane B2 by subjects on either of the diets. Urinary 2,3-dinor-thromboxane B2 excretion was lower (206.5 ng/24 h) when subjects were fed the high-omega 6 polyunsaturated fatty acid diet when compared with the lower-omega 6 polyunsaturated fatty acid diet (275.3 ng/24 h). Conversely, urinary prostaglandin E2 was higher (139.2 ng/g creatinine) during the higher-omega 6 polyunsaturated fatty acid diet when compared with the lower-omega 6 polyunsaturated fatty acid diet (94.4 ng/g creatinine).