2-3-dinor-6-ketoprostaglandin-f1alpha and Angina-Pectoris

Topics: 6-Ketoprostaglandin F1 alpha; Aged; Angina Pectoris; Humans; Male; Middle Aged; Physical Exertion; Thromboxane B2

Thromboxane released from activated platelets and prostacyclin of the vessel wall may act as potent antagonistic modulators of platelet aggregability and coronary vascular tone. Therefore, urinary excretion of their major metabolites, 2,3-dinor-thromboxane B2 and 2,3-dinor-6-ketoprostaglandin F1 alpha, was studied in 16 patients presenting with prolonged angina at rest. The 10 patients whose condition did not improve under vigorous antianginal treatment within 48 hours exhibited higher thromboxane metabolite excretion than did the 6 patients who responded to therapy (2,208 +/- 1,542 versus 609 +/- 312 ng/g creatinine; p less than 0.001). Elevated values were also found in four of eight patients with sustained postinfarction angina. Enhanced thromboxane metabolite excretion was frequently associated with angiographic evidence of thrombus formation. When nine patients were restudied in a stable phase after 11 +/- 5 months, thromboxane metabolite excretion was consistently normal or high normal. Excretion of prostacyclin metabolites was not depressed in any patient but correlated weakly with thromboxane (r = 0.41). Thus, enhanced thromboxane production as an index of platelet activation may identify patients with active thrombus formation who could benefit most from platelet inhibitory treatment.

Topics: 6-Ketoprostaglandin F1 alpha; Aged; Angina Pectoris; Angina, Unstable; Electrocardiography; Exercise Test; Female; Follow-Up Studies; Humans; Male; Middle Aged; Monitoring, Physiologic; Platelet Aggregation; Thromboxane B2

Pathological and clinical studies have suggested that platelets have a role in the pathogenesis of unstable angina and myocardial infarction. However, the relation of platelet activation to episodic ischemia in patients with unstable angina is unknown. We assessed the biosynthesis of thromboxane and prostacyclin as indexes of platelet activation in patients with stable and unstable coronary disease by physicochemical analysis of metabolites in plasma and urine. Prostacyclin biosynthesis was markedly elevated in patients with acute myocardial infarction and correlated with plasma creatine kinase (r = 0.795; P less than 0.001). The largest rise in thromboxane synthesis was observed in patients with unstable angina, in whom 84 percent of the episodes of chest pain were associated with phasic increases in the excretion of thromboxane and prostacyclin metabolites. However, 50 percent of such increases were not associated with chest pain, possibly reflecting silent myocardial ischemia. These data indicate that platelet activation occurs during spontaneous ischemia in patients with unstable angina. The increment in prostacyclin biosynthesis during such episodes may be a compensatory response of vascular endothelium that limits the degree or effects of platelet activation. If so, biochemically selective inhibition of the synthesis or action of thromboxane A2 would be desirable in the treatment of unstable angina. In contrast, thromboxane inhibitors or antagonists would not be expected to be effective in patients with chronic stable angina, in whom there was no increase in the formation of thromboxane A2.

Topics: 6-Ketoprostaglandin F1 alpha; Angina Pectoris; Angina, Unstable; Blood Platelets; Epoprostenol; Humans; Myocardial Infarction; Thromboxane A2; Thromboxane B2

The results of prior studies indicate that nitroglycerin stimulates prostacyclin release by cultured endothelium and by the coronary vasculature in vivo. However, the accuracy of these findings in coronary vasculature relies on plasma samples obtained from the circulation via cardiac catheters, a procedure we have shown to stimulate prostacyclin release, thereby confounding interpretation of drug action. We studied the effects of short-acting (nitroglycerin) and long-acting (isosorbide dinitrate) nitrates on a noninvasive index of prostacyclin synthesis, excretion of urinary 2,3-dinor-6-keto-PGF1 alpha. Nitroglycerin was infused into six subjects to either a maximum of 480 micrograms/min or until mean arterial pressure fell by 20 mm Hg. Urine was collected for negative ion chemical ionization gas chromatographic, mass spectrometric analysis before and during the nitroglycerin infusion and for two 2 hr periods after nitroglycerin. The peak nitroglycerin infusion rate was 387 +/- 67 micrograms/min, which caused a fall in supine blood pressure (systolic/diastolic) of 11 +/- 5/14 +/- 4 mm Hg and a 12 +/- 3 beats/min increase in heart rate. Excretion of 2,3-dinor-6-keto-PGF1 alpha (pg/mg creatinine) was unchanged from control infusion values (106 +/- 19.5) either during (123 +/- 21) or after (134 +/- 14.6; 139 +/- 36) nitroglycerin infusion. Platelet aggregation to arachidonic acid (0.33 to 1.33 microM) and epinephrine (1 to 10 microM) ex vivo was inhibited in only one subject in whom excretion of 2,3-dinor-6-keto-PGF1 alpha was unaltered. Serum thromboxane B2 was not changed by nitroglycerin infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Adult; Angina Pectoris; Arachidonic Acid; Arachidonic Acids; Blood Pressure; Epinephrine; Epoprostenol; Heart Rate; Humans; Isosorbide Dinitrate; Middle Aged; Nitroglycerin; Platelet Aggregation