GROWTH-HORMONE THERAPY INITIATED BEFORE STARVATION AMELIORATES THE CATABOLIC STATE AND ENHANCES THE PROTEIN-SPARING EFFECT OF TOTAL PARENTERAL-NUTRITION

The effect of 7 days of subcutaneously administered bovine growth horm one (bGH) (0.2 mg kg-1 day-1; n = 4) or an equivalent volume of 0.15 m ol l-1 saline (n = 3) on protein metabolism was assessed in lambs. The catabolic response to 48 h of starvation and subsequent hypocaloric t otal parenteral nutrition (TPN) was measured using primed constant int ravenous infusions of [N-15]urea and [C-14]leucine. Following 48 h of starvation and 7 h of TPN, bGH-treated animals had a significantly dec reased rate of net protein catabolism compared with controls (mean(s.e .m.) 2.4(0.2) versus 3.2(0.3) g kg-1 day-1, P < 0.01). The mean(s.e.m. ) rate of whole-body protein catabolism was also significantly decreas ed in bGH-treated animals at 10.9(0.3) g kg-1 day-1 compared with 12.9 (0.7) g kg-1 day-1 in saline-treated controls (P < 0.05). In addition, the rates of net and whole-body protein catabolism decreased signific antly (P < 0.05) during the period of hypocaloric parenteral feeding t o mean(s.e.m.) values of 2.3(0.2) and 8.6(0.6) g kg-1 day-1 respective ly in bGH-treated animals. By contrast, in saline-treated controls net and whole-body protein catabolism continued to increase during hypoca loric parenteral feeding. There was a significant decrease (P < 0.05) in the rate of [C-14]leucine uptake in tissues of the gastrointestinal tract, heart and diaphragm in bGH-treated animals compared with contr ols. These results demonstrate that daily administration of growth hor mone decreases the catabolic response to a metabolic stress, resulting in the conservation of protein in the heart, diaphragm, gastrointesti nal tract and musculoskeletal system by a primary anticatabolic action . In addition, growth hormone therapy initiated before induction of th e catabolic state enhances the protein-sparing effects of TPN. Further study is justified to determine whether growth hormone therapy initia ted before elective or urgent surgery in the nutritionally depleted pa tient may have a role in reducing the severity of the postoperative ca tabolic state, particularly in the patient in whom a complicated cours e is anticipated.