ACID-BASE HOMEOSTASIS PARALLELS ANABOLISM IN SURGICALLY STRESSED RATSTREATED WITH GH AND IGF-I

The effect of a standard surgical stress and subsequent total parenter al nutrition (TPN) treatment on systemic acid-base balance was assesse d in four groups of rats: TPN controls, TPN coinfused with recombinant human insulin-like growth factor I (rhIGF-I, 800 mu g/day), TPN with recombinant human growth hormone (rhGH, 800 mu g in two divided daily sc doses), and combined rhGH plus rhIGF-I (800 + 800 mu g/day). After the 6-day time course, TPN controls exhibited a systemic metabolic aci dosis (HCO3- = 20.4 +/- 0.4 mM) and lost 7 g body wt/6 days. Either gr owth actor ameliorated the acidosis (rhGH = 22.6 +/- 0.6 and IGF-I = 2 2.0 +/- 0.5 mM) and promoted weight gain (11 +/- 2 and 10 +/- 3 g/6 da ys, respectively). Combined growth factor treatment, rhGH + rhIGF-I, r estored acid-base balance (HCO3- = 24.7 +/- 0.6 mM) and exhibited an a dditive effect on weight gain (25 +/- 3 g/6 days). Ammonium and sulfat e excretion as indexes of renal acid excretion and systemic sulfuric a cid production, respectively, were highest in the TPN control. Growth factors alone reduced sulfuric acid production, whereas combined growt h factor treatment reduced acid production and eliminated acid excreti on despite elevated renal glutaminase activity. However, renal cortica l glutamate content was elevated in the combined growth factor treatme nt (10.6 +/- 0.7 vs. 7.3 +/- 0.5 rhGH + rhIGF-1 vs. TPN, P < 0.05), co nsistent with repression of the elevated glutaminase activity These fi ndings point to an important role for acid-base homeostasis in the ana bolic response and are consonant with an additive effect of growth fac tors, rhGH + rhIGF-I,in correcting the metabolic acidosis associated w ith surgical stress.