SYSTEMICALLY AND LOCALLY ADMINISTERED GROWTH-HORMONE STIMULATES BONE HEALING IN COMBINATION WITH OSTEOPROMOTIVE MEMBRANES - AN EXPERIMENTAL-STUDY IN RATS

Growth hormone (GH) is known to be of a major importance for longitudi nal bone growth, but its local effects on osteogenesis and, thus, rege neration of bone defects are less known. The aim of this investigation was to study whether GH, systemically or locally administered, has an y stimulatory effects on local osteogenesis, utilizing standardized, m embrane-covered, transosseous defects (5 mm diameter) in mandibles of adult albino rats. The study also addressed the question of whether GH might be a feasible option to further promote bone regeneration and n eogenesis in conjunction with expanded polytetrafluoroethylene (e-PTFE ) ''osteopromotive'' membranes (GORE-TEX(R)). Human GH (hGH; 0.2, 2, 2 0, 200 mu g/day), bovine GH (bGH; 200 mu g/day), prolactin (200 mu g/d ay) or saline was administered systemically by means of mini-osmotic p umps, implanted subcutaneously at the back of the animal. Healing was analyzed after 2, 3, and 4 weeks. Healing was also studied after local administration, just outside the defects, of hGH (0.2, 2, 20 mu g/day ) via catheters connected to mini-osmotic pumps during 4 weeks. Human GK and bGH stimulated local bone formation compared to saline and prol actin. Bone formation was significantly promoted by systemically admin istrated hGH, after 3 weeks and at 2 mu g/day or higher concentrations . Enhanced bone formation was also found after 4 weeks in animals give n 0.2, 2 and 20 mu g/day of hGH locally, compared to local administrat ion of saline. The results show that GH exerts a direct, nonliver medi ated effect on bone tissue. Moreover, the study suggests that hGH may be used to stimulate bone healing and formation in conjunction with os teopromotive membranes.