In vivo crevicular leukocyte response to a chemotactic challenge: inhibition by experimental diabetes

Diabetes in rats inhibits the migration of neutrophils into the healing gingival crevice, an effect associated with impaired in vitro neutrophil chemotactic activity. We recently described the in vivo response of human and rat crevicular neutrophils to a chemotactic challenge and used this assay in the present study on streptozotocin-induced diabetic rats. Optimal concentrations of two chemotactic agents, casein (0.2 mul, 2 mg/ml) or N-formylmethionylleucylphenylalanine (0.2 mul, 10(-4) M), were placed into the gingival crevices of control and diabetic rats (time zero) after the resting neutrophil count was measured. After a 15-min delay, the neutrophil counts and gingival crevicular fluid flow were assessed every 5 min for another 0.5 h. The control rats (n = 14) showed an increase in neutrophil counts which reached maximum levels 30 min after the N-formylmethionylleucylphenylalanine challenge ("peak" neutrophil response) and decreased dramatically 5 min later. Diabetes of 4 days (n = 4), 14 days (n = 8), and 20 days (n = 5) duration reduced the peak neutrophil response 45, 66, and 71%, respectively. Casein produced the same response as N-formylmethionylleucylphenylalanine in control rats. Uncontrolled diabetes of 20 days duration reduced the peak neutrophil response to casein by 83%; diabetics administered insulin on a daily basis showed a reduction of only 34%. The pattern of change in gingival crevicular fluid flow in response to chemoattractants paralleled the neutrophil response. The chemotactic activity of peritoneal neutrophils was assessed in vitro with the agarose gel technique and was found to be correlated (r = 0.84; P < 0.01) with the in vivo chemotactic response in the same rats. If the same in vivo defect is observed in humans with diabetes (or with other systemic diseases associated with leukocyte dysfunction), this test could be useful diagnostically to rapidly assess neutrophil chemotaxis in lieu of in vitro assays and to identify patients who are unusually susceptible to aggressive periodontal disease.