Biological and thrombolytic properties of fibrolase--a new fibrinolytic protease from snake venom.

Fibrolase, a direct-acting fibrinolytic enzyme has been shown to cleave primarily the A alpha and B beta chains of human fibrin. We have previously reported that fibrolase also exhibits fibrinogenolytic activity and acts mainly as an alpha-chain fibrinogenase. In contrast to the action of streptokinase (plasminogen activator), fibrolase does not activate plasminogen. In vitro thrombolytic efficacy of fibrolase was determined by monitoring the release of radiolabel from iodinated fibrin and human blood clots. Fibrolase effectively digested the clots in a dose-dependent manner. The in vivo efficacy of fibrolase was evaluated in an animal model of arterial thrombosis. Fibrolase was found to be efficacious at dissolving femoral arterial clots following a single intravenous bolus administration. Time to reperfusion was dose dependent and similar to that observed with streptokinase. No adverse effects on blood pressure and heart rate were observed.

Biochemical characteristics of fibrolase, a fibrinolytic protease from snake venom.

Fibrolase, a fibrinolytic enzyme isolated from Agkistrodon c. contortrix (southern copperhead) venom, solubilizes fibrin primarily by rapid hydrolysis of the alpha and beta chains. Fibrolase is also an A alpha, B beta fibrinogenase. The breakdown products of fibrin and fibrinogen following incubation with fibrolase were different from those observed with plasmin. This enzyme is a metalloprotease that was inhibited by ethylenediaminetetraacetic acid. Fibrolase was inhibited by dithiothreitol, suggesting that disulfide bonds are important for catalytic activity. It was also inhibited by alpha 2-macroglobulin, but not by the soybean or lima bean trypsin inhibitors, diisopropylfluorophosphate, or p-hydroxymercuribenzoate. Unlike thrombolytic agents such as streptokinase, fibrolase does not activate plasminogen as evidenced by the use of plasmin-specific chromogenic substrate S-2251 and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Effects of sucralfate or mild irritants on experimental gastritis and prostaglandin production.

Rats pretreated with dilute ethanol, dilute hydrochloric acid, or dilute sodium hydroxide had significantly less gastric mucosal damage when they were exposed 15 or 30 minutes later to strong irritants. The dilute agents, known as mild irritants, also caused an increase in the production of gastric mucosal prostaglandin E2 at the 15- and 30-minute dosing intervals. This suggests that the mild irritants are only effective in providing gastric mucosal protection when they increase gastric production of prostaglandin E2. Sucralfate treatment also caused an increase in gastric mucosal production of prostaglandin E2 at only the 15- and 30-minute dosing intervals. In contrast, pretreatment with sucralfate protected against the damaging effects of the strong irritants for at least 480 minutes. Therefore, prostaglandin E2 may play a role in sucralfate's protective effect at short dosing intervals, but at longer intervals, when prostaglandin E2 changes were not observed, sucralfate was still found to be very effective in reducing the severity of gastritis. This suggests that sucralfate acts, at least in part, through some other mechanism(s) besides increasing gastric mucosal prostaglandin E2 production.

Quantitation of diltiazem and desacetyldiltiazem in dog plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic procedure was developed for the determination of diltiazem and desacetyldiltiazem in dog plasma. Two milliliters of plasma is extracted with a hexane-2-propanol mixture. The assay uses a reverse-phase column maintained at 55 degrees C with a silica saturation column and a pellicular precolumn. The mobile phase is acetonitrile-water (50:50) at pH 6.6 with 1.5-g/L heptanesulfonic acid added as the ion-pair reagent. The procedure is sensitive to 5 ng/mL for both compounds in dog plasma and is linear up to 2000 ng/mL for diltiazem and 1000 ng/mL for desacetyldiltiazem . Preliminary dog mean plasma profiles of diltiazem and desacetyldiltiazem are presented.

Pharmacokinetics of diltiazem in selected animal species and human beings.

The absorption, distribution and elimination of diltiazem hydrochloride in rodent and canine species are reviewed. The drug is well absorbed but undergoes first pass metabolism after oral administration. Diltiazem is extensively distributed, and 52 to 81 percent is bound to serum protein, depending on the species studied. Diltiazem is metabolized in the liver by several pathways; deacetylation, N-demethylation, and O-demethylation are the primary degradative steps. The metabolites are excreted in urine and feces, indicating that biliary excretion occurs. There is some evidence for enterohepatic cycling. Diltiazem is rapidly eliminated (t 1/2 = 2.24 hours) in beagle dogs, and the relatively short half-life appears to be a result of the high level of plasma clearance (46.1 +/- 4.8 ml/min/per kg body weight). A comparison of the plasma diltiazem clearance with hepatic blood flow in the dog indicates that the drug is eliminated at a rate dependent on hepatic blood flow.

Color analysis of dextrose solutions using a color difference meter.

A method for quantitating color measurements in dextrose solutions by using a color difference meter is described. This method was shown to correlate well with standard American Public Health Association (APHA) color measurements. A mathematical relationship was developed relating yellowness index values to APHA numbers as described in the USP for dextrose solutions. This relationship was tested by comparing the results from standard APHA color tests on laboratory samples of autoclaved dextrose solutions to APHA numbers calculated from yellowness index values for the same samples.