Wound healing and thymotropic effects of arginine: a pituitary mechanism of action.

Supplemental dietary arginine HCl (ARG-HCl) minimizes immediate post-wounding weight loss, accelerates wound healing, and is thymotropic for uninjured and wounded rats. The present experiments were to determine if arginine-pituitary interactions underlie these effects because arginine is a growth hormone secretagogue. Effects of 1% dietary ARG-HCl supplements (0.5% added to a regular commercial rat diet containing 1.8% ARG, 0.5% in drinking water) were studied in (a) hypophysectomized (hypox) rats supplemented with ACTH, L-thyroxine, testosterone propionate, (b) such hypox rats additionally supplemented with bovine growth (hypox + bGH) hormone, (c) intact rats (Int), and (d) intact rats supplemented with growth hormone (Int. bGH). Group (a) hypox rats healed their wounds as rapidly as intact rats (dorsal skin incision breaking strength, accumulation of reparative collagen in sc polyvinyl alcohol sponges). Group (b) hypox, bGH rats showed increased wound breaking strength and accumulation of reparative collagen in the sc sponges to levels significantly greater than those of intact controls; bGH given to intact controls did not affect these indices of wound healing. Supplemental ARG-HCl given intact rats significantly minimized immediate postoperative weight loss, increased wound breaking strength and sponge reparative collagen accumulation, and increased thymic weight. None of these effects of supplemental ARG-HCl were observed in group (a) hypox rats or group (b) hypox + bGH rats. We conclude that an intact hypothalamic-pituitary axis is necessary for these beneficial effects of supplemental ARG-HCl given wounded rats.