We studied cellular resistance to copper of plant cells Polygonum cuspidatum. When callus of P. cuspidatum was incubated on medium containing 100 μM cupric sulfate, the callus grew as well as the control callus did. The copper content of the callus, however, was elevated to a similar level of the medium. When cell extracts of callus exposed to 100 μM cupric sulfate were fractionated by gel filtration chromatography, a specific copper peak was eluted at the region of molecular weights between 4000 and 10000. Since an appearance of the copper-containing materials was inhibited by buthionine sulfoximine and the partially purified copper-containing materials contained only three amino acids : glutamic acid, glycine and cystine, the materials were supposed to be γ-glutamyl peptides phytochelatins. Callus of P. cuspidatum synthesized phytochelatins from 50 μM cupric sulfate and maximally at 100-150 μM cupric sulfate. When induction of phytochelatins by another heavy metal, zinc, was analyzed, the callus, however, did not synthesize phytochelatins on exposure to zinc sulfate up to 1 mM. These findings suggested that phytochelatins were required for resistance to copper but probably not to zinc in the plant cells.
Effects of a tiaramide derivative, 5 chloro-3-(4-hydroxypiperadinocarbonylmethyl) benzothiazoline-2-one (HPR-611), on anaphylactic chemical mediator release from rat peritoneal exudate cells (RPEC), guinea pig lung fragments (GPLF) and human lung fragments (HLF) were investigated in comparison with those of tiaramide and disodium cromoglycate (DSCG). HPR-611 at 10-6-10-4 g/ml showed a concentration-dependent inhibition of the histamine release from RPEC regardless of its pretreatment time. Tiaramide also inhibited the release with slightly less potency than HPR-611. The treatment of DSCG 1 min before antigen challenge markedly prevented the release but the inhibitory potency was clearly deteriorated by prolongation of the pretreatment time. Tiaramide tended to influence the anaphylactic release of histamine from GPLF with only 20% inhibition of the release at either 10-5 or 10-4 g/ml, whereas HPR-611 at 10-5 and 10-4 g/ml significantly suppressed the release in a concentration-dependent fashion. DSCG was not effective on that even at higher concentrations. Anaphylactic release of not only histamine but also immunoreactive leukotriene B4 (i-LTB4) and i-LTC4 from HLF was markedly inhibited by 10-8-10-4 g/ml of HPR-611. Tiaramide inhibited the release to a somewhat less extent than HPR-611, while nominal or no inhibitions by DSCG were found. From these results, it is clearly apparent that anti-allergic actions of HPR-611 are quite different from those of DSCG.
The absorption and excretion of 1, 3-bis-(2-ethoxycarbonylchromon-5-yloxy)-2-((S)-lysyloxy) propane dihydrochloride (N-556), which is a prodrug for the oral delivery of disodium cromoglycate (DSCG), were studied in rats and rabbits. In both animal species, the plasma concentration of DSCG after oral administration of N-556 peaked within 1.0 h, and thereafter declined with a half-life of about 1.2 h in rats and rabbits. The area under the plasma DSCG level versus time curve (AUC) increased in proportion to the dose of N-556 in both animals. The bioavailability of N-556 as calculated from AUC was about 6% in rats and 40% in rabbits, whereas that of DSCG was only 0.1% in rats and 2.5% in rabbits. About 2% and 15% of the dose were respectively excreted as DSCG in the urine and bile after the oral administration of N-556 in rats. The ratio of biliary excretion to urinary excretion (B/U) after the oral administration of N-556 was about twice that after the intravenous injection of DSCG. In rabbits, the urinary and biliary excretions of DSCG after oral administration of N-556 were about 25% and 5%, respectively. The B/U ratio after the oral administration of N-556 in rabbits was similar to that after intravenous administration of DSCG. The difference in the systemic bioavailability of N-556 between rats and rabbits thus appears to be due to a first-pass effect, in addition to a difference in the absorption rate.
Effects of nanomolar to submillimolar carteolol, a non-selective β-antagonist, on the evoked release at 1 Hz and the spontaneous release in the absence and presence of uptake1 and uptake2 blockers were studied in pulmonary arteries, isolated from guinea pigs, and then preloaded with [3H] noradrenaline. dl-Carteolol at 10-8, 10-7 and 10-6 M applied at the increasing concentrations inhibited the evoked [3H]-release in untreated arteries and in desipramine and corticosterone-treated arteries. The spontaneous [3H]-release slightly but significantly increased or tended to increase in untreated arteries. dl-Carteolol at 10-5 and 10-4 M clearly and concentration-dependently increased the spontaneous [3H]-release in untreated and cocaine-treated arteries. This increase was markedly inhibited by further pretreatment with normetanephrine. The evoked [3H]-release was not altered by dl-carteolol at 10-5 M, but increased at 10-4 M. This increase was not modified by cocaine and by cocaine and normetanephrine. d-Carteolol at 10-5 and 10-4 M produced effects similar to those of dl-carteolol. Nanomolar to micromolar dl-carteolol inhibits the evoked [3H]-release, which supports our previous conclusion that this inhibition is due to blockade of tonically functioning presynaptic β2-adrenoceptors. Carteolol at the higher concentrations seems to become a substrate for an uptake2 mechanism and to produce an unknown sympathomimetic activity in guinea pig pulmonary arteries.
Male Sprague-Dawley rats were given either 6.5 or 8.5 mg/kg of iv cisplatin combined with three injections of sc methylprednisolone in doses of either 50, 100 or 250 mg/kg at -4, 0 and 4 h after the cisplatin injection. Blood urea nitrogen and serum creatinine levels were determined on day 5 following the cisplatin injection. The protective effects of methylprednisolone on cisplatininduced nephrotoxicity were clearly demonstrated. Our preliminary results suggest that a much higher dose of cisplatin could be injected in cancer chemotherapy, if it was combined with methylprednisolone.