AJP - Endocrinology and Metabolism, Vol 250, Issue 3 231-E235, Copyright © 1986 by American Physiological Society
A direct growth effect of growth hormone in rat hindlimb shown by arterial infusion
N. L. Schlechter, S. M. Russell, S. Greenberg, E. M. Spencer and C. S. Nicoll
We have developed a method for infusing substances into one hindlimb of the
rat via the arterial supply. A catheter attached to an osmotic minipump is
inserted into the right superior vesical artery and advanced to the
junction of the right common iliac artery. This arrangement permits either
constant or pulsatile infusion for 7 days. We employed this method to study
the direct action of rat growth hormone (rGH) on the proximal tibial
epiphysial plate in hypophysectomized rats. Infusion of neither the solvent
nor ovine prolactin (2 micrograms X rat-1 X day -1) affected epiphysial
plate width compared with control (uninfused) legs. The rGH infused at 0.4
and 2.0 micrograms X rat-1 X day-1 produced dose-related local growth
effects that were of similar magnitude with either constant or pulsatile
(eight 1-h pulses/day) infusion. However, the higher dose of rGH also
resulted in a systemic effect (i.e., epiphysial plate growth in the
uninfused limb), and the pulsatile mode produced a greater systemic effect
than that produced by constant infusion. Our results indicate that GH can
act directly on cartilage in vivo to maintain growth and that its
effectiveness is not enhanced by pulsatile delivery. In contrast, the
indirect (i.e., systemic) growth effects of the hormone may be enhanced by
intermittent infusion. Our infusion system is well suited for studying the
direct effect of substances on hindlimb tissues in conscious, unrestrained
rats over extended periods.
