Carrie A. Branch

Relaxation of porcine coronary artery to bradykinin : role of arachidonic acid

Bradykinin-induced relaxation of precontracted, porcine coronary artery (PCA) rings is mediated by distinctly different endothelium-derived relaxing factors depending on the contractile agent used. Thus when contracted with KCl, bradykinin-induced relaxation of PCA rings is mediated solely by nitric oxide (NO), whereas when contracted with the thromboxane mimetic U46619, a small component of the relaxation is attributable to NO and a large component is attributable to a non-NO mechanism that is independent of cyclooxygenase activity. We hypothesized that the non-NO component was mediated by arachidonic acid (AA) or by a non-cyclooxygenase product of AA metabolism. Bradykinin-induced relaxations of PCA rings precontracted with U46619 in the presence of indomethacin (10 mumol/L) were moderately attenuated by the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME, 100 mumol/L), whereas when precontracted with KCl, L-NAME abolished the relaxations. AA produced endothelium-dependent relaxations of rings precontracted with U46619 that were unaffected by L-NAME, whereas AA did not relax rings precontracted with KCl. In rings precontracted with U46619, in the presence of L-NAME and indomethacin the phospholipase inhibitors quinacrine (50 mumol/L) and 4-bromophenacyl bromide (10 mumol/L) attenuated bradykinin- but not AA-induced relaxations. Inhibitors of both lipoxygenase (BW 755c [100 mumol/L] and nafazatrom [20 mumol/L]) and cytochrome P-450 (proadifen [10 mumol/L] and clotrimazole [10 mumol/L]) pathways did not eliminate bradykinin- or AA-induced relaxations, although clotrimazole partially attenuated AA-induced relaxations. These findings suggest that bradykinin-induced relaxation of PCA rings is mediated by AA through a mechanism that is not dependent on cyclooxygenase, lipoxygenase, or cytochrome P-450 pathways.

Phencyclidine and violent deaths in St. Louis, Missouri: a survey of medical examiners' cases from 1977 through 1986

A survey of 104 deaths involving phencyclidine (PCP) occurring from 1981 through 1986 in metropolitan St. Louis, Missouri, is presented. Four black males (22-33 yr) died from fatal PCP intoxication. PCP was detected in an additional 100 deaths: 81 homicides, 13 suicides, and 6 accidental deaths. Seventy-five of these deaths were homicides of Black males (mean age 27 years) typically dying from gunshot wounds, 64 cases. In 50% of deaths where PCP was detected, other drugs were co-administered: ethanol (35%) and cocaine (20%) being the most common mixtures. A dramatic continuous increase in PCP abuse from 1984 through 1986 was demonstrated by drug abuse indicator data: treatment admissions, emergency room episodes, police exhibits, and driving under the influence of PCP arrests. Increased abuse of PCP in St. Louis has been associated with increased medical emergencies and violence against persons.

Dichotomous cardiac and systemic vascular responses to cocaine in conscious rats

This study examined the effects of cocaine on cardiac output in conscious freely-moving rats. Although pressor responses were similar at all doses, 14 of 32 rats had consistent declines in cardiac output (> 15%) and greater increases in systemic vascular resistance after administration of cocaine (5 mg/Kg, i.v.). Procaine (10 mg/Kg i.v.) did not mimic this effect in either subgroup. We propose that a subpopulation of rats exists with an enhanced susceptibility to cocaine-induced cardiac and systemic vascular alterations at higher doses.

Coronary arterial lesions in dogs treated with an endothelin receptor antagonist.

Structurally and pharmacologically diverse vasodilators are known to lower blood pressure, increase heart rate, and produce acute injury to right coronary arteries in the dog. Administration of low concentrations of endothelin-1 (ET-1) to anesthetized dogs causes coronary vasoconstriction and reductions in coronary blood flow. Therefore, pharmacologic blockade of endothelin receptors (ETA and ETB) with the mixed ET receptor antagonist SB 209670 could lead to coronary vasodilatation. In toxicology studies, continuous administration of SB 209670 to dogs for 5 days at 50 micrograms/kg/min was associated with minor but sustained increases in heart rate (10-30 beats/min), slight decreases in mean arterial pressure (10-15 mm Hg), and medial hemorrhage and necrosis of extramural coronary arteries in the right atria. Doses of 10 micrograms/kg/min had no effect. The lesions in the right atrium were associated with the highest density of ET receptors, approximately 470 fmol/mg compared to 170-200 fmol/mg in the ventricles and septum. Because changes in systemic cardiovascular parameters are minimal, the coronary arterial lesion is most likely due to a local vasodilatory effect in the coronary bed.

Calcium channel antagonists reduce the cocaine-induced decrease in cardiac output in a subset of rats.

Intravenous (i.v.) cocaine administration elicits a decrease in cardiac output (CO) in some but not all rats. In the present study, we examined the effects of L-type calcium channel antagonists on cardiovascular responses in conscious freely moving rats with a cocaine-induced decrease in CO. Arterial blood pressure (ABP), heart rate (HR), and CO (pulsed Doppler flowmetry) were measured, and estimates of changes in systemic vascular resistance (SVR), stroke volume (SV), and rate-pressure product (RPP) were calculated from these values. After recovery, rats were treated with cocaine (5 mg/kg, i.v.) to ascertain their myocardial responses. Some rats demonstrated a decrease in CO, usually during the peak pressor response after cocaine administration, whereas others experienced only slight increases in CO. Rats demonstrating a minimum 15% decrement in CO were pretreated with either verapamil or nifedipine before cocaine was read-ministered. Verapamil (150 μg/kg) or nifedipine (100 μg/ kg) selectively reduced the peak fall in CO and the increase in SVR after cocaine administration, whereas nifedipine (25 μg/kg) had little effect on these parameters. Neither drug affected the pressor response to cocaine. These data suggest that calcium channel antagonists can selectively reduce cocaine-induced decreases in CO and increases in SVR without reducing afterload in a subset of rats sensitive to the cardiodepressive effects of cocaine.