IMPACT OF UREMIA ON FOOD EFFICIENCY AND THE PULSATILE MODE OF GROWTH-HORMONE SECRETION IN RATS

In view of the profound growth failure resulting from renal insufficie ncy and uraemia, the present studies were designed to specifically inv estigate food efficiency and the pattern of GH secretion under these c onditions. Animals were made uraemic by 5/6 nephrectomy (Nx) and feedi ng a high-protein diet. Three groups of animals were studied: uraemic (Ur); sham-operated, fed ad libitum (Sh); and sham-operated pair-fed w ith the uraemics (PF). Food intake per 100 g body weight and food effi ciency (g weight gained per g food consumed) were calculated. Fourteen days after 5/6 Nx, blood samples were taken via intra-atrial catheter s at 10-min intervals over a period of 6 h. GH was measured in plasma by radioimmunoassay. GH pulsatility was analysed by multiple parameter deconvolution. The growth rate of Ur animals was significantly lower than that of Sh. The body weights of the Ur animals were also lower th an PF due to an initial period of weight loss. Both Sh and PF animals showed the typical negative slope of food intake as body weight increa sed. In contrast, the Ur animals showed a positive slope of food intak e. The lower rate of growth and the elevated food intake corresponded to a decreased food efficiency for the Ur group. Deconvolution analysi s of pulsatile GH release demonstrated a significant increase in GH ha lf-life in the Ur animals. The amplitude and mass of GH secretory puls es were decreased, whereas the number of detectable secretory bursts w as increased. These changes were specific to uraemia with respect to h alf-life and number of pulses. We conclude that uraemia results in a d ecrease in the conversion of food to body mass, which is accompanied b y significant changes in the neuroregulation of pulsatile GH secretion .