Inhibition of d-aminolevulinate dehydratase is not closely related to the development of hyperglycemia in alloxan-induced diabetic mice Verˆ onica B. Brito a,b , Jo ~ ao Batista T. da Rocha a , Gustavo O. Puntel a,c , Sˆ onia Cristina A. da Luz d , Nilda B.V. Barbosa a , Nelson R. de Carvalho a , Vanderlei Folmer a,c,n a Departamento de Quı ´mica, Centro de Ciˆ encias Naturais e Exatas, Universidade Federal de Santa Maria, UFSM, CEP 97105-900, Santa Maria, RS, Brasil b Centro de Quı ´mica e Bioquı ´mica, Departamento de Quı ´mica e Bioquı ´mica, Faculdade de Ciˆ encias da Universidade de Lisboa, UL, P-1749-016, Lisboa, Portugal c Universidade Federal do Pampa, UNIPAMPA, Campus de Uruguaiana, BR 472-KM 592, CEP 97500-970, Uruguaiana, RS, Brasil d Departamento de Patologia, Centro de Ciˆ encias da Sau ´de, Universidade Federal de Santa Maria, UFSM, CEP 97105-900, Santa Maria, RS, Brasil article info Article history: Received 7 May 2009 Accepted 7 March 2010 Keywords: Alloxan Mice d-ALA-D Hyperglycemia Diabetes Sulfhydryl groups abstract Alloxan is a compound widely used in models of diabetes mellitus due to its ability for damage insulin- producing b-cells. The aim of this study was to investigate acute (after 24 h) and sub-acute (after seven days) effects of 200 mg/kg alloxan administration on mice. Biochemical parameters as liver, kidney, and blood d-ALA-D activity, total sulfhydryl content of hepatic and renal tissues, and hepatic and renal content of malondialdehyde (MDA) were evaluated. The histopathology of hepatic and renal tissues of alloxan-treated and control animals was carried out. Further, blood glucose levels were determined in an attempt to correlate alloxan-induced hyperglycemia with changes in thiol status. Results showed that mice exhibited a significant inhibition of hepatic and renal d-ALA-D activity in addition to a significant decrease in total sulfhydryl groups of same tissues in both acute and sub-acute alloxan administrations. Moreover, alloxan-induced inhibition of d-ALA-D activity was partly suppressed when enzymatic assay was performed in the presence of dithiothreitol, suggesting that inhibitory effect of alloxan on d-ALA-D activity is, at least partially, related to the oxidation of the enzyme’s essential thiol groups. Blood d-ALA-D activity was significantly inhibited only 24 h after alloxan administration; however, at this time, a hyperglycemic status was not observed in animals. In contrast, a significant increase in blood glucose levels was observed seven days after alloxan administration. Despite of alterations in biochemical parameters, histological tissue examination of alloxan-treated mice revealed typical renal and hepatic parenchyma. Therefore, these results showed that acute toxic effects of alloxan are related, at least partially, to depletion of sulfhydryl groups, and do not closely relate to the development of hyperglycemia in mice. & 2010 Elsevier GmbH. All rights reserved. Introduction Diabetes mellitus describes a group of metabolic disorders characterized by chronic hyperglycemia that generally results from a deficiency in insulin secretion or a decreased ability to transduce insulin signal. This metabolic disease leads to severe long-term complications as heart disease, kidney failure, and blindness (Resnikoff et al., 2004; Chaturvedi, 2007), where hyperglycemia and polyol pathway disruption have been gen- erally implicated (Brownlee, 2001). Though acute manifestations of diabetes can often be managed clinically by insulin therapy, progressive secondary complications are the major cause of chronic illness and high mortality (Bo et al., 2006). In the past decades, molecular mechanisms underlying in these complica- tions were thoroughly investigated and evidences suggested that glucose-mediated non-enzymatic reactions such as autoxidation, proteins cross-linking, and advanced glycation end-products (AGEs) formation (Fu et al., 1994; Brownlee, 1995) were involved. Moreover, studies concerning deleterious effects of hyperglyce- mia on properties of physiologically important proteins such as hemoglobin, albumin, and collagen (Schwartz, 1995; Day et al., 1997; Sajithlal et al., 1998) were made. Tetrapyrrole molecules are essential for aerobic organisms since constitute prosthetic groups of physiologically important proteins as hemoglobin and cytochromo (Sassa, 1998). Heme prosthetic group is a component of hemeproteins present in all human tissues, which play a central role in several cellular metabolic processes. Heme biosynthesis is impaired in a group of diseases named as porphyrias, mainly porphyria cutanea tarda, in which there is higher incidence of diabetes mellitus and glucose Contents lists available at ScienceDirect journal homepage: www.elsevier.de/etp Experimental and Toxicologic Pathology 0940-2993/$ - see front matter & 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.etp.2010.03.003 n Corresponding author at: Universidade Federal do Pampa, UNIPAMPA, Campus de Uruguaiana, BR 472, Km 592, CEP 97500-970, Caixa Postal 118, Uruguaiana, RS, Brasil. Tel.: + 55 3413 4321; fax: + 55 3414 1484. E-mail address: vanderfolmer@gmail.com (V. Folmer). Experimental and Toxicologic Pathology 63 (2011) 443–451