Evaluation of the mutagenicity of formaldehyde in mammalian cytogenetic assay in vivo and vitro. Mutat Res ; Mutagenic characteristics of formaldehyde on bacterial systems. Aldehydes: occurrence, carcinogenic potential, mechanism of action and risk assessment.
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The oxidation of glutaraldehyde by rat tissues W. Korb, BS D. Pashley, DDS, PhD Abstract Glutaraldehydeis used in pediatric dentistry as an alternative to formocresolin the treatment of primaryteeth with diseased pulpal tissue. A 10, g "mitochondrial" subfraction was prepared from kidney and incubated with glutaraldehyde , DPM. It is concludedthat glutaraldehydecan be metabolizedin living systems.
Concern over the clinical use of formocresol as a pulpal fixative stems from doubts about its clinical effectiveness Magnusson , local irritating effects Block et al. Glutaraldehyde has been suggested as the potential pulpotomy agent of choice to replace formocresol Davis et al. Although glutaraldehyde, a bifunctional reagent, is an effective protein cross-linking agent and, therefore, a powerful fixative Dawes ; Ranly and Lazzari , little information is available concerning the metabolism of this compoundin the body Horton This paper presents data on the metabolism of glutaraldehyde in rat tissue.
Boston, Massachusetts. DL-isocitrate, trisodium salt, alpha-ketoglutarate, disodium salt, glutaric acid, and humanserum albumin free fatty acid free-Fraction V were purchased from Sigma Chemical Co. Louis, Missouri. All other chemicals were reagent grade. Tissue Preparation Adult, ad libitum-fed Fisher inbred rats were sacrificed by decapitation and kidney, liver, muscle, and hearts collected and immediately cooled on ice.
For the slice experiments, four rats were sacrificed simultaneously and slices made from the liver, gastrocnemius muscle, kidney, and the heart of each animal. Slices from each specific tissue from all animals were pooled and randomized by stirring gently. For preparation of a "mitochondrial" fraction, kidneys were removed, weighed, and homogenized in 10 volumes 0. The whole homogenate was centrifuged at g for 10 min and the supernatant recentrifuged at 10, g for another 10 min.
The resulting 10,g pellet was labeled the mitochondrial fraction and resuspended in ml 0. Incubations The pooled slices approximately mg, total wet weight were incubated in 2 ml of Krebs-Ringer bicarbonate buffer containing about , DPM14C-glutaraldehyde.
The center wells filled with hyamine hydroxide were dropped into scintillation vials containing ReadySolv HP. Incubations were performed in triplicate and CO2 collected and measured as described above. The authors routinely ran no-enzymecontrols and subtracted the results from the experimental incubations. Protein was measured using the Lowry assay Lowry et al. Humanserum albumin was used a standard. Control experiments in which est activity.
Furthermore, oxidation of glutaraldehyde the slices were first boiled and then incubated, routinely occurs in the mitochondria fraction, not the 10, g produced about DPMCO supernatant fraction. The data are consistent with the 2. In order to provide additional evidence that 14CO2is produced from glutaraldehyde enzymatically, the oxidation of glutaraldehyde in rat kidney mitochondria was studied as a function of incubation time and protein concentration. Figure I shows the results obtained when incubation time was varied over 2 hr.
Figure 2 shows the results of varying the amount of protein in the incubation. Glutaraldehyde oxidation by bation. Whenthe 10, g supernatant 4. The basic tion of protein concentration. Points on the curve represent the meanof triplicate determinameanof triplicate determinations. Comparing the metabolism of glutaraldehyde with formaldehyde, previous work has shown that formocresol is absorbed and distributed rapidly throughout the body within minutes of being placed on a pulpotomy site. In addition, only a very small fraction of formaldehyde is metabolized to 14CO2; most formaldehyde is tissue bound Pashley et al.
In contrast, glutaraldehyde has a very low tissue binding Myers et al. These observations support the replacement of formaldehyde with glutaraldehyde as a pulpotomy agent for primary teeth. It is possible that glutaraldehyde may be metabolized similarly to other aldehydes, such as acetaldehyde. Much research has centered on acetaldehyde metabolism Thurman , because of interest in this aldehyde as an intermediate in alcohol metabolism.
Whether glutaraldehyde is acted upon by the same enzymes that metabolize acetaldehyde, or more specific enzymes, possibly glutaraldehyde dehydrogenases and semialdehyde dehydrogenases, needs to be investigated. This may indicate that both alpha-ketoglutarate and dlisocitrate stimulated 14CO2by stimulating the tricarboxylic acid cycle. The decrease in 14CO2 produced in the presence of glutaric acid may be due to an isotopedilution effect or the inhibition of glutaraldehyde oxidation by glutaric acid.
Further study is needed to clarify the role of alpha-ketoglutarate, dl-isocitrate, and glutaric acid in glutaraldehyde oxidation. These data are considered important because they illustrate that a tissue fixative presently being used in dentistry, glutaraldehyde, can be metabolized in rat. The level at which glutaraldehyde ceases to be a dental tissue fixative and instead becomes a metabolite needs to be investigated.
The authors thank Ms. Lois Phillips for her expert technical assistance with part of this project. Karp is an associate professor, oral biology, oral medicine and pediatrics, and Dr. Korb was an NIDRsummer research trainee at the time of the study. Reprint requests should be sent to: Dr. Karp, Depts. Block RMet al: Antibodyformation to dog pulp tissue altered by formocresolwithin the root canal. Oral Surg, Davis MJet al: Glutaraldehyde: Analternative to formocresol for vital pulp therapy. J DentChild , Burlington; LaddResearchIndustries, Inc, Horton AA: Mitochondrial metabolism of aldehydes.
Biochem J PP, J AmDent Assoc, LowryOHet al: Protein measurement with the folin phenol reagent. J Biol Chem, MagnussonBO: Therapeutic pulpotomies in primary molars with the formocresoltechnique. Acta OdontolScand, MunksgaardEC et ah Dentin-polymer bond promoted by Gluma and various resins. J DentRes , Pediatr Dent , J Dent Res , RobertsonA et al: Oxidationof palmitate by humanplacental tissue slices.
Physiol Chem Physics , NewYork and London; PlenumPress, These data are considered important because they illustrate that a tissue fixative presently being used in dentistry, glutaraldehyde, can be metabolized in rat tissue. Vicky Caldas Cueva. Published on Apr 8, Go explore.
2005, Número 4
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