Effect of growth hormone on the inflammatory activity of experimental colitis in rats

The effect of daily treatment with 2.0 mg biosynthetic human growth hormone per kilogram body weight or isotonic NaCl (controls) on experimental colitis was investigated in rats. Colonic inflammation was induced by instillation of trinitrobenzene sulfonic acid (TNB) intraluminally into the left colon. Untreated NaCl-instilled rats were used for comparison with intact colon. Four days after TNB instillation the growth hormone-treated rats had lower macroscopic and microscopic damage scores and less infiltration of neutrophils, measured as myeloperoxidase activity (MPO), than controls. The biomechanical properties of the colon showed that the breaking strength and energy absorption were reduced in the control rats with colitis compared with intact colon, whereas the rats treated with growth hormone had unchanged strength and energy absorption. The differences in MPO activity, damage scores, and biomechanical properties were associated with a higher concentration of insulin-like growth factor I in serum from growth hormone-treated rats after 4 days than controls. Finally, the growth hormone-treated rats regained their initial body weight after 7 days, in contrast to the body weight of control rats, which remained 11% lower than their initial body weight.