1. Short and long-term effect of growth hormone on basal and catecholamine induced lipolysis in pigs The Message Short-term treatment with growth hormone results in a decrease in catecholamine induced lipolysis. Conversely, long-term treatment results in an increase, suggestive of differential regulation Introduction Long-term growth hormone (GH) administration results in an increase in lean and a decrease in fat mass. GH increases lean mass indirectly via the insulin-like growth factor-1 (IGF-1) axis. Fat mass is thought to be decreased by GH acting directly on adipose tissue resulting in: -inhibition of lipogenesis -facilitation of lipolysis (particularly catecholamine induced) Short-term effects of GH on lipolysis are not as well documented. This study aims to compare the short and long-term effects of GH administration in vivo on ex vivo basal and catecholamine (isoproterenol) induced lipolysis. Methods 32 Large White male pigs Fed ad libitum diet of 18% crude protein (14MJ/kg) Control (n=10) 28 daily i.m. injections of vehicle Short-term GH (n=11) 21 daily i.m. injections of vehicle, 7 daily i.m. injections of GH (5mg Reporcine) Long-term GH (n=11) 28 daily i.m. injections of GH (5mg Reporcine) Day 28 all pigs slaughtered Plasma collected for IGF-1 analysis Perirenal adipose tissue removed from 4 pigs/group (n=12) Transported in supplemented M199 media (37°C) Chopped in supplemented Krebs-Ringer Bicarbonate buffer (KRB, 37°C) Cultured in KRB ± Isoproterenol (100mM) for 3hrs, 37°C Media removed for glycerol quantification (Sigma kit 337-B) Fat collected for lipid content determination (Folch extraction) GH x Isoproterenol (IP) interaction p<0.001, Dunnetts test compares 7 and 28 day GH treatments to the appropriate control (± IP) * p<0.05, **p<0.01 Results Conclusions Body composition was unaffected by GH treatment with the exception of liver weight, which increased after short- term GH treatment Plasma IGF-1 increased with both short and long-term GH treatment Short and long-term GH administration had no effect on basal lipolysis Short-term (7 day) GH treatment decreased IP stimulated lipolysis Long-term (28 day) GH treatment increased IP stimulated lipolysis This study demonstrates the opposite effects of short and long-term GH treatment on IP stimulated lipolysis. Similar work in sheep (Doris et al. 1996) has shown an increase in IP stimulated lipolysis after 7 day GH administration, the opposite of our 7 day findings. However, this is more consistent with our 28 day data. Thus it appears that the direction of the GH effect is dependent on both species and duration of treatment. Katie R. Headland 1, Paul L. Sensky 1, Peter J. Buttery 1, Keith Dickinson 2 and John M. Brameld 1 1 Division of Nutritional Biochemistry, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD 2 RenaSci, Biocity, Nottingham, NG1 1GF Doris RA, Thompson GE, Finley E, Kilgour E, Houslay MD, Vernon RG (1996) Journal of Animal Science 74: 562-568 Katie R Headland is funded by a BBSRC CASE studentship with RenaSci RenaSci