Environmental Toxicology and Pharmacology 23 (2007) 132–134 Short communication Nitrate and nitrite concentrations in rabbit saliva Comparison with rat saliva S. Djekoun-Bensoltane a , M. Kammerer b,∗ , M. Larhantec b , N. Pilet b , C. Thorin b a Laboratoire de Toxicologie Cellulaire, Facult´ e des Sciences, Universit´ e Badji-Mokhtar, 23000 Annaba, Algeria b Unit´ e de Pharmacologie et Toxicologie, Ecole Nationale V´ et´ erinaire de Nantes, BP 40706, 44307 Nantes Cedex 3, France Received 7 March 2006; received in revised form 21 July 2006; accepted 31 July 2006 Available online 4 August 2006 Abstract The purpose of this work was to investigate the interest of rabbits for studying pharmacology and toxicology of dietary nitrate. Twenty-one females were given 1, 300 and 600 mg/l nitrate in drinking water for 11 weeks. Saliva and blood were analysed for nitrate/nitrite. There is a linear relationship between the amounts of nitrate ingested and amount of nitrate in saliva, contrary to what is observed in rats. However, salivary nitrite concentrations remain low, and nitrate reductase activity in the oral cavity of the rabbit seems very weak. © 2006 Elsevier B.V. All rights reserved. Keywords: Nitrate; Nitrite; Saliva; Rabbit; Rat; Drinking water 1. Introduction Study of nitrate metabolism shows that major pathway for elimination is urinary excretion, but salivary secretion is also of significant importance with regard to a qualitative and quanti- tative viewpoint. Indeed, in humans, nitrate is actively secreted by salivary glands, and the level of nitrate in saliva is much higher than in blood (Eisenbrand et al., 1980). Nitrate is then partially reduced to nitrite by the oral microflora, which can have beneficial or detrimental consequences. It can be advan- tageous because, on account of bactericidal properties, salivary nitrite is protective against dental caries, and infections from infected food and water (Doel et al., 2004; Duncan et al., 1997). But it could be toxic too, because nitrite is responsible for infan- tile methaemoglobinemia and is implicated in the formation of carcinogenic N-nitroso compounds (Badawi et al., 1998; Krul et al., 2004; Shapiro et al., 1991). These properties and hypotheses justify carrying out studies about secretion and occurrence of nitrate and nitrite in saliva. Many kinetic studies are realized on healthy volunteers, but investigations which are harmful must be carried out on animals. Most of these experimental studies are ∗ Corresponding author. Tel.: +33 2 40 68 77 77; fax: +33 2 40 68 77 42. E-mail address: kammerer@vet-nantes.fr (M. Kammerer). conducted in rats, but it is known that the salivary secretion in this species is not similar to that in humans. Therefore, it seems necessary to explore salivary secretion of nitrate and nitrite in other species. Miniature pig could be interesting, but its use as laboratory animal is still uncommon. So we worked on rabbits, in order to investigate the interest of this experimental model in the study of pharmacology and toxicology of these ions in humans. 2. Material and methods 2.1. Animals New Zealand white rabbits, HY PLUS strain, were purchased (Grimaud 49450, Roussay, France) as 6-weeks-old females. The 21 rabbits were divided into 3 groups of 7 animals each, and were supplied with water containing 1 mg/l (control group: group C), 300 mg/l (group 300) and 600 mg/l nitrate (group 600). Drinking water was prepared from bottled spring water for human consumption by addition of NaNO 3 solution. The assay was conducted over a period of 11 weeks, because its aim was at the same time of salivary study to explore the effects of nitrate on immunitary cells. Animals were housed in individual cages, according to GLP. Drinking water was available ad libitum from individual bot- tles. Rabbits were fed on pelleted standard diet (88% dry matter, DM), containing a very low nitrate level (7.8 mg/kg DM). In order to compare results, a fuller assay was carried out in rats in the same conditions. 12 Wistar rats of both sexes (6 males and 6 females) were divided into 3 treatment groups, 2 males and 2 females each, two animals of the same 1382-6689/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.etap.2006.07.007