AJP - Endocrinology and Metabolism, Vol 252, Issue 2 E268-E272, Copyright © 1987 by American Physiological Society
Secretory pattern of canine growth hormone
M. B. French, P. Vaitkus, E. Cukerman, A. Sirek and O. V. Sirek
Our aim was to define the secretory pattern of growth hormone (GH) under
basal conditions in fasted, conscious, male dogs accustomed to handling.
Blood samples were withdrawn from a cephalic vein at 15-min intervals. In
this way, any ultradian rhythms, if present, could be detected within the
frequency range of 0.042-2 cycles/h. In addition, samples were drawn at
either 1- or 2.5-min intervals for 2.5 or 5 h to determine whether
frequency components greater than 2 cycles/h were present. GH was measured
by radioimmunoassay and the raw data were submitted to time series analysis
employing power spectral estimation by means of fast Fourier transformation
techniques. Peak plasma levels were up to 12 times higher than the baseline
concentration of approximately 1 ng/ml. Spectral analysis revealed an
endogenous frequency of 0.22 cycles/h, i.e., a periodicity of 4.5 h/cycle.
The results indicate that under basal conditions the secretory bursts of
canine GH are limited to one peak every 4.5 h.
