July 2012

Background: Nifedipine, a calcium channel-blocking agent, has been associated with gingival enlargement in humans. This enlargement has also been successfully established in animal models. Previous investigators have administered nifedipine through a systemic route, most commonly by oral intake. The aim of the present study was to measure the effects of nifedipine administered directly into rat gingival interproximal papillae. Methods: Twenty-four adult female rats were assigned to three groups. Each animal received a series of three injections, one week apart; each injection was placed directly into the interdental papilla of the maxillary and mandibular central incisors. Group 1 (control) received only saline. Group 2 received a low (10 μg/ml) concentration of nifedipine, while Group 3 received a higher concentration (500 μg/ml). One week after the last series of injections, gingival specimens were harvested from the injection site and prepared for histological and immunocytochemical analyses. Results: Specimens from Group 3 displayed a significantly greater number of ED2-positive cells compared to the other two groups. Specimens from Group 2 showed a significantly higher mean count of positive cells compared to Group 1. Collectively, our data suggest that repeated local injections of 10 μg/ml and 500 μg/ml nifedipine each elicit an inflammatory response in the gingival connective tissue. Conclusions: Immunocytochemical analysis revealed dose-dependent increases of resident tissue macrophages in rats receiving nifedipine (p < 0.005). An increased inflammatory infiltrate also was observed via routine histology. Gross macroscopic changes consistent with gingival enlargement were not observed.