Growth hormone action is blunted by acidosis in experimental uremia or acid load

The effects of rhGH (H) daily injection (2 IU/d) and of vehicle (V) during two weeks were studied in young (60 g) growing rats. Experiment I was performed in uremic rats (mean plasma creatinine: 65-71 mumol/l) either acidotic (mean HCO3-:11.5 mmol/l: UAH, n = 20; UAV, n = 18), or with corrected acidosis by addition of NaHCO3 in the diet (mean HCO3-:26 mmol/l: UBH, n = 25; UBV, n = 23). Experiment II used rats with normal renal function (plasma creatinine: 25 mumol/l), either non-acidotic but food restricted to the dietary intake of uremic rats (CRH: n = 18, CRV: n = 18), or rendered acidotic by NH4Cl (CAH: n = 16, CAV: n = 16). GH induced an augmentation of body weight and length gains in non-acidotic uremic rats (+33% and +41%: p < 0.01), and in non-acidotic food restricted rats (+13% and 42%: p < 0.05 and p < 0.0001). This was associated with increased protein synthesis rate in muscle and with little change of food intake as well as of plasma IGF 1. Plasma IGF 1 kept the same relationship to food intake, regardless of treatment, but length gain for each level of plasma IGF 1 was enhanced by GH in GH responding groups. In both acidotic rat groups, GH altered none of the parameters studied. Thus: 1) the presence of severe metabolic acidosis blunts the response to GH in uremic and non-uremic rats. 2) The increment of growth rate does not depend on a rise of plasma IGF 1.