Substance P levels in the rectal mucosa of diabetic patients with normal bowel function and constipation.

Substance-P content in rectal mucosa was determined by radioimmunoassay in 28 diabetic patients (17 with severe chronic constipation and 11 with normal bowel function), 24 non-diabetic patients with severe functional constipation, and 27 normal controls. Substance-P content (pg/mg) in the rectal mucosa of diabetics with normal bowel function was significantly higher than that of non-diabetic controls (p < 0.001). Substance-P content in the rectal mucosa of diabetics with constipation was more than double that of patients with non-diabetic functional constipation (p < 0.01) and lower than that of diabetics with normal bowel function (p < 0.0375). Diabetic patients (constipated and non-constipated) have higher substance-P content in the rectal mucosa than non-diabetics. Lower substance-P rectal mucosa content in constipated diabetic patients than in non-constipated diabetics supports a possible role of substance P in the pathogenesis of diabetic constipation.