Effect of the GH secretagogue L-163,255 and restricted feeding time on GH pulsatility in the rat.

Objective: To determine the effect of repeated treatments with the growth hormone secretagogue (GHS) L-163,255 on the pulsatile release of GH when administered in meal-fed rats before and after feeding. Design: The first group of rats (AL, na 6) had food available ad libitum. The second (restricted, R, na 6), third (GHSB, na 6), and fourth (GHSA, na 6) groups were fed from 1100 to 1400 h. Groups GHSB and GHSA were given GHS by gavage, 3.0 mg/kg L-163,255, at 1000 h (before feeding, B) and at 1500 h (after feeding, A) respectively. Three weeks after the initiation of the treatment, blood samples were collected at 10-min intervals over 6 h, and GH levels were determined. Results: In group R, the concentrations of GH were higher before feeding O17:6^2: 4n g=mlU than during feeding O11:2^1: 2n g=mlU; P , 0:05: The average concentrations of the peak in response to GHS were higher when GHS was administered beforeO121:70^33:68 ng=mlU than afterO49:67^ 17:87 ng=mlU feeding. The mass of GH, as calculated by deconvolution analysis was also higher in the GHSB group than in the GHSA group O251:6^64: 1n g=ml per min vs 85:3^22: 9n g=ml per min respectively, P , 0:05). Conclusion: L-163,255 is effective in inducing GH release after repeated oral administration in rats. The effectiveness is greater when GHS is administered before rather than after feeding in meal-fed animals.