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 insufficiency and uraemia, the present studies were designed to specifically investigate food efficiency and the pattern of GH secretion under these conditions. Animals were made uraemic by 5/6 nephrectomy (Nx) and feeding a high-protein diet. Three groups of animals were studied: uraemic (Ur); sham-operated, fed ad libitum (Sh); and sham-operated pair-fed with the uraemics (PF). Food intake per 100 g body weight and food efficiency (g weight gained per g food consumed) were calculated. Fourteen days after 5/6 Nx, blood samples were taken via intra-atrial catheters 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 than 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 increased. In contrast, the Ur animals showed a positive slope of food intake. The lower rate of growth and the elevated food intake corresponded to a decreased food efficiency for the Ur group. Deconvolution analysis of pulsatile GH release demonstrated a significant increase in GH half-life in the Ur animals. The amplitude and mass of GH secretory pulses were decreased, whereas the number of detectable secretory bursts was increased. These changes were specific to uraemia with respect to half-life and number of pulses. We conclude that uraemia results in a decrease in the conversion of food to body mass, which is accompanied by significant changes in the neuroregulation of pulsatile GH secretion.