Kinetics, mechanism and toxicity of intermediates of solar light induced photocatalytic degradation of pindolol: Experimental and computational modeling approach.

In this work, we have investigated the stability of pindolol (PIN), a non-selective ß1-blocker detected in the river and wastewater of hospitals, in water solution under solar irradiation. Further, detailed insights into the stability of PIN were obtained by the density functional theory (DFT) calculations and molecular dynamics simulations. The kinetics of PIN photocatalytic degradation and mineralization has been studied using four commercial photocatalysts ZnO and TiO2 (P25, Hombikat, and Wackherr). It was found that the major role in degradation of PIN play the reactive hydroxyl radicals. The structures of degradation intermediates were suggested by LC-ESI-MS/MS and DFT calculations. Also, DFT calculations were used to refine molecular structures of intermediates and obtain their geometries. Toxicity of PIN and its mixtures formed during photocatalytic degradation were investigated using mammalian cell lines (H-4-II-E, HT-29, and MRC-5). The H-4-II-E cell line was the most sensitive to PIN and its photodegradation mixtures. The computational results were combined with the experimental data on the amounts of degradation intermediates for determination of the intermediates that were principally responsible for the toxicity. Intermediate with two hydroxyl groups, positioned on indole ring in meta and para positions, was proposed as the one with the highest contribution to toxicity.

Toxicity of beta-blockers in a rat whole embryo culture: concentration-response relationships and tissue concentrations.

Beta-adrenoceptor blockers are widely used drugs for the treatment of cardiovascular diseases. Since beta-blockers cross the placenta, it is essential to consider possible adverse effects on the embryo. Six beta-adrenoceptor blockers were tested at various concentrations (10-5000 microM) in a rat whole embryo culture. Although inducing a very similar pattern of dysmorphogenetic effects (incomplete flexure, disturbed development of the neural tube, the head, the heart and the tail bud), the compounds exhibited a wide range of embryotoxic potency. Estimation of the EC50 (median-concentration producing dysmorphogenesis in 50% of the embryos) for the six compounds revealed differences of more than two orders of magnitude: propranolol 25 microM, alprenolol 30 microM, metoprolol 100 microM, pindolol 150 microM, acebutolol 500 microM, atenolol 4000 microM. Measurements of the concentrations of the various drugs in the cultured embryos at corresponding EC50 levels showed differing values: metoprolol 4.5 microM, propranolol 5.2 microM, alprenolol 8.4 microM, pindolol 9.0 microM, acebutolol 12.5 microM and atenolol 77.0 microM. With regard to the EC50 and the degree of substance transfer to the embryo it can be stated that propranolol and metoprolol show a much higher intrinsic potency to interfere with normal in vitro embryonic development than, e.g. atenolol.

Chronotoxicity of beta-adrenoceptor blocking agent in spontaneously hypertensive rats.

1. Chronotoxicity of a single LD50 dosage of beta-adrenoceptor blocking agent, pindolol, was determined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto control rats (WKY). 2. The 24 h mortality was greater when pindolol was administered at 00.00 h than when it was administered at 12.00 h in both SHR and WKY. 3. The chronogram of the mortality in SHR was similar to that in WKY. 4. These results indicate that the mode of circadian variation in the acute toxicity of pindolol in SHR is not different from that in WKY.

A toxicological review of beta-adrenergic blockers.

The use of various beta-adrenergic blockers has become extensive as they have been found to be efficacious in the treatment of a number of cardiovascular problems including cardiac arrhythmias, angina pectoris, and hypertension. The widespread and chronic use of these drugs has generated a concern for their potential chronic toxicity. Eighteen beta-adrenergic blockers have been reviewed and the available literature pertaining to their potential carcinogenicity, mutagenicity, and teratogenicity has been summarized and compared.

The effect of fasting on oral acute toxicity of drugs in rats and mice.

The oral acute toxicity of 3 beta-adrenoceptor stimulants, 2 beta-adrenoceptor blockers, and 2 anti-gastric ulcer drugs was studied in 8-week old, SD-JCL rats and ICR-JCL mice, fasted overnight for 17-20 hours. The results were compared with those from rats and mice allowed to feed normally. The order of the fed:fasted ratio of LD50 values in rats was pirenzepin less than propantheline less than pindolol less than salbutamol less than orciprenaline less than fenoterol less than bunitrolol, and was in the range 1.3-4.7. The increased toxicity in fasted animals was considered to be related to acceleration in gastric emptying and intestinal absorption, but not to a general change in the condition of the test system or a decrease in the detoxification ability of the liver because after intraperitoneal administration acute toxicity was similar in fed and fasted rats.