Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 51, Issue 6 B439-B447, Copyright © 1996 by The Gerontological Society of America
Sixteen weeks of hexarelin therapy in aged dogs: effects on the somatotropic axis, muscle morphology, and bone metabolism
SG Cella, CG Cerri, S Daniel, V Sibilia, A Rigamonti, L Cattaneo, R Deghenghi and EE Muller
Department of Pharmacology, University of Milan, Italy.
Hexarelin (HEXA; 500 micrograms/kg/die, s.c.) was administered for 16 weeks
to six old beagle dogs. The treatment consisted of three on-drug periods
spaced by two off-drug periods. During each on period, the growth hormone
(GH) peak response to HEXA initially increased and then dropped to
pretreatment values. Each time, a wash-out interval restored the same
pattern of GH responsiveness. HEXA significantly augmented the indices of
spontaneous pulsatility of GH, but plasma insulin-like growth factor I
levels did not change during treatment. HEXA apparently reduced bone
resorption since it significantly decreased the urinary concentration of
lysylpyridinoline, a bone matrix component. Bone formation apparently was
not affected since unchanged levels of alkaline phosphatase were recorded.
In three of six old dogs, HEXA induced an improvement of some morphological
and biochemical muscular indices, evaluated in muscle specimens that,
instead, remained unchanged in a group of young untreated controls. These
findings indicate that HEXA effectively releases GH and primes the
pituitary of old dogs, and strengthen the view that in aging, GH secretion
may be restored by pharmacological means. It would also appear that HEXA-
induced GH release improves some indices of body composition in old dogs.
