| Abstract: | The effects of intracoronary leukotriene C4 (LTC4) and D4 (LTD4) (both 0.1 microgram/kg) were studied in 23 anesthetized open-chest dogs at normal (= mean aortic pressure) and reduced (51 +/- 2 and 32 +/- 2 mm Hg) coronary perfusion pressures. The left anterior descending coronary artery was cannulated and blood flow measured. Subendocardial fiber segment length was obtained with ultrasonic crystals. At normal coronary perfusion pressure, LTC4 and LTD4 reduced coronary blood flow from 81 +/- 6 and 78 +/- 7 ml/min per 100 g by 41 +/- 4% and 41 +/- 4% (both p less than 0.0005), respectively. However, segment length shortening was not depressed by LTC4 or LTD4. At reduced coronary perfusion pressure, LTC4 and LTD4 diminished coronary blood flow from 35 +/- 5 and 32 +/- 3 ml/min per 100 g, by 28 +/- 5% (p less than 0.0025) and 30 +/- 5% (p less than 0.005). Thus, reduction of coronary blood flow was less by both LTC4 (p less than 0.01) and LTD4 (p less than 0.05) at reduced rather than at normal coronary perfusion pressure. Segment length shortening was depressed by LTC4 from 6.5 +/- 1.2% to 2.4 +/- 1.6% (p less than 0.05) and by LTD4 from 5.6 +/- 1.4% to 3.1 +/- 0.9% (p less than 0.05), respectively. Indomethacin (5 mg/kg, i.v.) and nifedipine (10 micrograms/kg, i.v.) did not abolish the LT-induced coronary artery constriction. However, in animals pretreated with indomethacin or nifedipine, reduction of coronary blood flow by LTs was not attenuated at reduced coronary perfusion.(ABSTRACT TRUNCATED AT 250 WORDS) |
