Gingival hyperplasia in rats induced by oxodipine--a calcium channel blocker

Oxodipine, a new calcium channel blocker, induced gingival hyperplasia in rats. This is the first time that a calcium channel blocker has been documented as resulting in gingival hyperplasia in rats. In contrast to diphenylhydantoin, the hyperplastic changes induced by oxodipine were not precipitated by any prior irritation. The histology consisted of purely fibroblastic proliferation without infiltrate of inflammatory cells.

Activities of newly synthesized dihydropyridines in overcoming of vincristine resistance, calcium antagonism, and inhibition of photoaffinity labeling of P-glycoprotein in rodents

Newly synthesized 1,4-dihydropyridine derivatives (NK-compounds) were screened to determine whether they could overcome vincristine (VCR) resistance in VCR-resistant (P388/VCR) leukemia-bearing mice. Among the 57 NK-compounds examined, six compounds had strong reversing ability (Grade A), 18 partially overcame the resistance (Grade B), and 33 did not reverse the resistance (Grade C). The ability to overcome resistance varied considerably with the nature of substituents at positions 3.5 of the 1,4-dihydropyridine, and the most suitable substituents were the pyridylalkyl-including esters. Calcium antagonistic activity of NK-compounds having pyridylalkyl-including esters at positions 3.5 and dithiene ring at position 4 of the 1,4-dihydropyridine was greater than in those compounds having the dioxene ring at position 4. NK-242, which was assessed at Grade A and had no calcium antagonistic activity, improved therapeutic effects in both VCR-sensitive (P388/S) leukemia- and P388/VCR leukemia-bearing mice when combined with VCR. Fourteen NK-compounds were screened to determine whether they could inhibit photoaffinity labeling of the P-glycoprotein (Mr 170,000 glycoprotein) in a multidrug-resistant cell line by [3H]azidopine. All six compounds of Grade A and two of the three compounds of Grade B almost completely inhibited the labeling of Mr 170,000 glycoprotein at 1 to 10 microM. Thus there was a good correlation between the ability to reverse VCR resistance in vivo and the inhibition of photoaffinity labeling of Mr 170,000 glycoprotein.

Iron chelators: in vitro inhibitory effect on the liver stage of rodent and human malaria

The activity of desferrioxamine (Desferal) and desferrithiocin (a newly developed oral iron chelator) was evaluated against the liver stage of Plasmodium yoelii and P. falciparum in the rodent and the human hepatocyte in vitro culture system. The two iron chelators were found to inhibit the liver schizogony of both the rodent and the human Plasmodium species at concentrations achievable in vivo. P. falciparum proved to be more sensitive (ic 95% below 20 micromol/l than P. yoelii (ic 95% 50-100 micromol/l). As assessed by electron microscopy, drug administration was associated with focal clarification of the cytoplasm thought to be reversible. As desferrioxamine and desferrithiocin are known to be equally active on the blood stage of rodent and human plasmodia, iron chelators are deserving of further investigation as potential alternative candidates to existing drugs for radical cure of malaria.

A dihydropyridine conjugate which generates high and sustained levels of the corresponding pyridinium salt in the brain does not exhibit neurotoxicity in cynomolgus monkeys

Many drugs can be selectively delivered to the brain by using a dihydropyridine in equilibrium pyridinium salt chemical delivery system (CDS). The interaction of these systems with central dopaminergic function was examined in this communication. Castrate female Sprague-Dawley rats when treated with a CDS for estradiol (i.e. 3-hydroxy-17 beta-[( (1-methyl-1,4-dihydropyridin-3-yl)carbonyl]oxy) estra-1,3,5(10)-triene or E2CDS) exhibit sustained and profound suppression of serum levels of leuteinizing hormone (LH). Treatment of rats with pargyline (80 mg/kg) prior to E2CDS (2 mg/kg) did not mitigate the biological effectiveness of this estrogen indicating at least indirectly that monoamine oxidate (MAO) was not involved in the CDS activation. In a more direct examination, cynomolgus monkeys treated with various repeated doses of E2CDS (cumulative doses of 0.2-40.0 mg/kg) demonstrated neither impaired motor function nor depleted striatal dopamine concentrations. The latter parameter was measured using liquid chromatographic-electrochemical analysis. These experiments support the contention that the CDS is not neurotoxic and further strengthens the strict structure-activity requirements for MPTP-induced neurotoxicity.

Gingival hyperplasia in dogs induced by oxodipine, a calcium channel blocking agent

Subchronic oral exposure of dogs to Oxodipine, a new calcium channel blocker of the dihydropyridine-type, resulted in dose-related gingival hyperplastic changes. The doses at which an effect was elicited were 24 and 73 times the intended therapeutic dose for man. The effects were first noted after 7 weeks of treatment, and were limited to the high and intermediate dose groups of both sexes. Macroscopically, a generalized enlargement of the maxillary and mandibular facial and lingual gingivae were noted. The histological changes were similar to those described in man for Nifedipine and hydantoin-related drugs. An increase in the activity of alkaline phosphatase and a decrease in alanine aminotransferase was demonstrated. This article is the first to describe gingival hyperplasia in dogs induced in a dose-dependent manner by a calcium channel blocker.

Synthesis and preliminary pharmacological studies on dihydropyrido-1,3,4-triazepinone derivatives

New 4,5-dihydropyrido-[2,3-e]-1,3,4-triazepin-5-one derivatives (2-9) were synthesized. The preliminary pharmacological tests revealed antinociceptive action of compounds 4-7 and 9 and antianxiety action of compound 4.