121 ESTIMATION OF THE EFFECT OF TESTOSTERONE (T) ON PROTEIN METABOLISM USING 15N

In 7 boys with short stature aged 11 years 9 month to 14 years 10 month growth hormone secretion was estimated by provocative stimuli after T-priming. By that occasion the influence of T on protein metabolism using 15N-tracer technique was investigated. 10 mg T/m2 body surface area was administered daily for 5 days. On the 3rd day 13.5 mg [15N] glycine per kg body weight were given orally and urine was collected for the following 3 days. The results of the excretion of 15N and total N in urine were calculated using a 3 pool model and compared with a basal period of 3 days after application of [15N] glycine but without T.T-adminlstration resulted in an increase of the rate of protein synthesis from 0.677 ± 0.37 mmol N/kg·h (M±SD) to 1.47 ± 0.37 nmol N/kg·h (p < 0.001) and of the N-fluz from 1.28 ± 0.54 to 1.64 ± 0.42 mnol/kg·h (p<0.05). The protein utilization increased from 51 ± 9.3% to 67 -7.6 % (p < 0.01), while the conventional whole N-retention, estimated without using 15N, did not change significantly. The results clearly demonstrate the advantage of 15N-tracer studies for investigating the metabolic effects of T.