Role of serum nonsuppressible insulin-like activity (NSILA) in wound healing. I. Influence of thyroparathyroidectomy on serum NSILA and wound healing in the rat.

Serum contains a 90,000 molecular weight glycoprotein that exhibits insulin-like activity on adipocytes, skeletal muscle, and fibroblasts in tissue culture; however, this protein is physicochemically and immunochemically distinct from insulin and presently is termed "nonsuppressible insulin-like activity ("nsilA)." This study was designed to assess the response of serum NSILA to thyroparathyroidectomy (TPTHX) and to associate this response with tissue repair processes in the injured rat. It was postulated that NSILA modulates the fibroblastic response in wound healing. TPTHX decreased NSILA to 40 percent of control levels (p less than 0.001); 90 male animals subsequently were wounded by either a 10 percent third-degree burn or skin excision. Following injury, NSILA significantly increased in both control and TPTHX groups, but this acute-phase response was attenuated in TPTHX animals. Light microscopy of granulation tissue demonstrated a diminution in the fibroblastic response in TPTHX animals. Hydroxyproline analysis of granulation tissue revealed a significant decrease (p less than 0.025) in collagen content in TPTHX animals with low NSILA levels. The results suggest that serum NSILA levels are controlled, in part, by thyroid hormone and that NSILA may modulate the fibroblastic response of connective tissue repair processes.