Blake B. Coldwell

Increased ethanol toxicity in old rats: Changes in LD50, in vivo and in vitro metabolism, and liver alcohol dehydrogenase activity

Abstract Old rats (10–12 months old) were significantly more susceptible to acute ethanol poisoning than young adult rats (3–4 months old). The LD50 in young rats was 10.6 (po) and 6.71 (ip) g/kg compared to 7.06 (po) and 5.10 (ip) g/kg in the older animals. The slopes of the dose-response lines were very steep and the LD100 dose in the old animals was always substantially less than the LD0 in the young rats. Following a single ip dose of 3 g/kg, the brain and blood ethanol levels were significantly higher in the older animals and decreased at a slower rate. The decay profiles for acetaldehyde and acetone in blood and brain were more complex. Liver slices taken from older rats metabolized ethanol at a slower rate per gram of tissue than did slices from younger animals. The alcohol dehydrogenase levels per gram of tissue were significantly higher in the 1-year-old rats, and the total liver alcohol dehydrogenase activity was 3-fold greater.

The estimation of acetylsalicylic acid and salicylate in biological fluids by gas-liquid chromatography

A gas‐liquid chromatographic method is described for the simultaneous separation and determination of acetylsalicylic acid (ASA) and salicylic acid (SA) in biological fluids. The salicylates are completely extracted from deproteinized plasma or urine at pH 2 with ether containing p‐toluic acid as the internal standard. The silylated derivatives are formed using bis(trimethylsilyl) trifluoroacetamide and separated at 150° on preconditioned 100–120 mesh Gas‐Chrom Q coated with 5% OV17 packed into a 6 ft, 1/4 inch o.d. glass column in a gas chromatograph with a flame ionization detector and integrator. Detector response is linear over the range from 0–2 mg ml−1 for SA and from 0–100 μg ml−1 for ASA. The time required for the analysis of SA alone or with ASA is about 80 min, the analysis of ASA alone requires about 20 min. The precision of the method is 1 % or better for drug concentrations above 10 μg ml−1. The limits of detectability for SA and ASA are 1 and 2 μg ml, respectively.

Interaction of cannabinoids with pentobarbital in rats

The effect of cannabidiol (CBD), cannabigerol (CBG), cannabinol (CBN), Δ8-tetrahydrocannabinol (Δ8-THC), and Δ9-tetrahydrocannabinol (Δ9-THC) on the in vivo metabolism of [14C]pentobarbital (14C-P) was investigated in rats. The cannabinoids were administered ip (20 mg/kg) 30 min prior to either oral or iv treatment with 14C-P. When 14C-P was given po, the 14C blood concentrations were initially depressed and later elevated by CBG and CBD, increased by Δ8-THC and Δ9-THC and unaffected by CBN. When 14C-P was injected iv, the blood 14C values were elevated by CBD and unchanged by CBG, Δ8-THC or Δ9-THC. Urinary excretion of total 14C and the metabolites of P was decreased by CBD, CBG and Δ8-THC during the first 6 hr following treatment. The effect of CBD on the blood concentration and urinary excretion of 14C was dose-related. In rats treated with CBD + P, the liver and serum concentrations of P metabolites were significantly lower and the liver, serum and brain concentrations of unmetabolized P were significantly higher than in P-treated rats. Pentobarbital induction and sleeping times were potentiated by CBD and Δ9-THC and antagonized by CBG. It was concluded that CBD delayed P metabolism, CBG decreased the rate of P absorption and excretion. Δ8-THC and Δ9-THC decreased elimination of P and CBN had little effect on P absorption, metabolism or excretion. The effect of CBD + P on sleeping time was correlated with brain P concentrations.

Effect of sodium salicylate on the fate of warfarin in the rat

Abstract Salicylate (88.9 mg/kg, po) decreased the blood level of radioactivity emanating from [ 14 C]warfarin (1 mg/kg, iv and po) during the 24 hr following drug administration, reduced the area under the blood radioactivity vs time curve, and shortened the half-life for elimination of radioactivity from the blood. During the first 6 hr after drug administration, salicylate increased the biliary excretion of radioactivity, which resulted in enhanced fecal excretion of warfarin and its metabolites. Salicylate administration initially increased and later decreased the amount of radioactivity in the liver, and increased the proportion of warfarin metabolites to unchanged warfarin in this organ. It did not affect the proportion of unchanged warfarin to metabolites in the blood, bile and urine, or the total amount of radioactivity excreted during 48 hr in the urine and feces. In vitro, salicylate decreased the binding of [ 14 C]warfarin to rat serum proteins in a linear manner. It is concluded that, in the rat, salicylate competes with warfarin for serum protein binding sites, thereby facilitating its uptake by the liver. Second, through a combination of its choleretic action and effect on membrane transport, salicylate enhances the biliary excretion of warfarin and its metabolites, thus accounting for the decreased concentration in the blood and lowered antiboagulant action.

Effect of aspirin on the fate of bishydroxycoumarin in the rat

Coldwell & Zawidzka (1968) showed that the oral administration of a single dose of aspirin (100 mg/kg) to male rats on a regimen of the anticoagulant drug, bishydroxycoumarin, decreased the one-stage prothrombin time of blood collected 20 h after administration of the analgesic. Subsequently, this action of aspirin was observed in female and male rats after chronic dosing and was produced even more intensely by an equivalent amount of sodium salicylate, while several other analgesics were without any effect (Zawidzka & Coldwell, 1970). Analysis of the serum samples obtained from some of these animals for bishydroxycoumarin, using the spectrophotometric method of Nagashmia, Levy & Nelson (1968), suggested that aspirin might be affecting the serum bishydroxycoumarin concentration. This lead to the possible mechanism of the observed anti-bishydroxycoumarin effect of aspirin and sodium salicylate has now been investigated further. Male albino rats of the Wistar strain, 175-200 g, acclimatized to the laboratory environment for at least one week, were dosed intraperitoneally with bishydroxycoumarin daily for 3 days at 2.0, 1.5 and 1.5 mg/100 g, respectively. The dose administered on day 3 included 171-4 pg/lOO g of [14C]bi~hydr~xyc~umarin having a specific activity of 2.58 mCi/mmol. Simultaneously with the administration of bishydroxycoumarin on day 3, aspirin (100 mg/kg )was administered orally to 6 of the 11 animals. The animals were then placed immediately in metabolism cages with free access to water ; food was made available for a short period 24 h after the final drug administration. Tail blood specimens (10 pl) were taken at 0.5, 1, 2,4,7, 12, and 24 h and urine and faeces were each collected over the periods from 0 to 24 h and 24 to 48 h after the final drug administration. The samples were analysed for radioactivity using an accepted liquid scintillation counting procedure (radioactivity is expressed as unmetabolized bishydroxycoumarin). The blood decay profiles for bishydroxycoumarin in the presence and absence

Effects of thioridazine and diazepam on the pharmacokinetics of [14C]imipramine in rat: acute study

The pharmacokinetics of [14C]imipramine (10 mg kg−1) were tested in male Wistar rats for interaction with thioridazine (16 mg kg−1) or diazepam (10 mg kg−1). All drugs were administered orally with the test substances being given 40 min before [14C]imipramine dosing. Bile and urine were collected for 90 min after the radioactive drug was given. The animals were then killed and the tissues removed. Thioridazine reduced the excretion of radioactivity into the bile and urine, and increased the weight of the contents within the gastrointestinal tract. These effects were interpreted as being mainly due to a reduction in gastrointestinal motility resulting in a slower stomach emptying of [14C]imipramine. No effect on metabolism was detected. Diazepam pretreatment reduced the concentration ratio of radioactivity in the small intestinal contents to that of plasma, but did not alter the tissue distribution, metabolism or excretion of [14C]imipramine.

Effect of acetylsalicylic acid, caffeine, and codeine on the metabolism of phenacetin in the rat

The effect of acetylsalicylic acid (ASA), caffeine, and codeine on the metabolism of [14C]phenacetin was studied in the rat. The blood concentration profiles of radioactivity were altered by ASA but not by caffeine and codeine. It was suggested that ASA reduced the rate of phenacetin absorption and elimination. Paper chromatography of urine showed that ASA reduced the excretion of N-acetyl-p-aminophenol (NAPA)-sulfate and increased the excretion of NAPA-glucuronide and a metabolite tentatively assumed to be NAPA-mercapturate. A tissue distribution study showed that the highest concentrations of radioactivity were found in the liver and kidney. Paper chromatography of tissue extracts gave evidence that conjugation of NAPA is inhibited by ASA. Thin-layer chromatography of chloroform extracts of plasma gave no indication that ASA affected the dealkylation of phenacetin to NAPA. Caffeine and codeine at the dose used had no significant effect on the tissue distribution or metabolism of phenacetin.