Modulation of neutrophil activity by submandibular gland peptide-T (SGP-T).

The heptapeptide submandibular gland peptide-T (SGP-T; sequence = Thr-Asp-Ile-Phe-Glu-Gly-Gly) was isolated from rat submandibular glands based on its ability to reduce endotoxic hypotension. Since these glands also modulate neutrophil function, the effects of SGP-T on neutrophil function were investigated. I.v. SGP-T (35 and 100 micrograms/kg), when administered prior to and after the s.c. implantation of a carrageenan soaked sponge into rats, significantly reduced the accumulation of neutrophils in the sponge. Neutrophils retrieved from saline soaked sponges generated substantial amounts of superoxide anion in response to both phorbol myristate acetate (PMA) and N-fornyl-methionyl-leucyl-phenylalanine (fMLP), whereas those obtained from carrageenan impregnated sponges were refractory to these oxidative stimuli. Treatment with SGP-T promoted a dose-dependent recovery in the ability of neutrophils obtained from carrageenan soaked sponges to generate superoxide anion. This study, by identifying SGP-T as a regulator of neutrophil function, supports the concept that salivary glands are involved in the regulation of inflammatory responses.