The effects of cyclosporine on varying segments of small-bowel grafts in the rat.

The relationship between the cyclosporine A (CSA) dose and rejection of varying lengths of small-bowel grafts was studied in a rat heterotopic microsurgical small-bowel transplantation model involving a haploidentical strain combination. When Lewis X Brown Norway F1 hybrid (LBN) small-bowel grafts were transplanted into Lewis (LEW) rats without CSA, all grafts in the proximal 10 cm, the proximal 40 cm, and the entire (approximately 80 cm) small bowel were rejected on days (mean +/- SEM) 6.6 +/- 0.2 (n = 11), 7.0 +/- 0.4 (n = 6), and 7.8 +/- 0.7 (n = 6), respectively. A 10-day course (days 0-9) of CSA 2 mg/kg significantly (p less than 0.05) prolonged the survival of the proximal 10 cm, the proximal 40 cm, and the entire small bowel allografts to days 18.8 +/- 1.7 (n = 5), 16.5 +2- 1.3 (n = 6), and 13.5 +/- 1.0 (n = 4), respectively. Similarly, the CSA 5 mg/kg regimen significantly (p less than 0.05) delayed the rejection of the 10 cm, the 40 cm, and the 80 cm small-bowel grafts to days 50.2 +/- 7.2 (n = 6), 47.7 +/- 2.6 (n = 3), and 40.3 +/- 5.8 (n = 3), respectively. However, 6 of 12 rats treated with CSA 5 mg/kg died of pneumonia, and these animals were all in groups with the 40 cm and 80 cm grafts. When these animals were included in calculations of rejection-free survival, the averages for the 40 and 80 cm groups treated with CSA 5 mg/kg were 34.2 +/- 6.4 and 28.7 +/- 6.1 days, respectively. CSA suppressed rejection of small-bowel allografts in a dose-related fashion. More important, significantly (p less than 0.05) lower doses of CSA were necessary for rats that received shorter intestinal grafts. In fact, the relationship between rejection and CSA dose in the 10 cm grafts was characterized by the formula: day of rejection = 9.3 [CSA dose]1.03. We conclude that the ideal small intestinal graft should be the smallest possible segment that maintains adequate nutrition and CSA doses should be matched for segment lengths.