Response of trace element concentrations in plasma of sheep to chronic
infusion of a recombinant variant of IGF-1
J. Lee, J.R. Rounce, J.E. Hocking Edwards, P.M. Harris
AgResearch, Private Bag 11008, Palmerston North, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1995,
55: 179-182
As part of a study measuring the effect of a variant of insulin-like
growth factor-1 (long-arg3-IGF-1; LR3IGF) on tissue amino acid utilisation
in sheep, changes in plasma Cu, Fe and Zn concentrations were observed.
LR3IGF-1 was infused continuously over 21 days into the skin of 6 sheep
using a bilateral arterio-venous preparation. Another 6 sheep were infused in
the same way with saline only (controls). Feed intakes were the same for
both groups. Arterial blood samples were obtained prior to the start of
treatment and at 1, 7, 14 and 21 days. Plasma samples were prepared and
analysed for concentrations of endogenous IGF-1, insulin, cerulophasmin,
macro-elements (Ca, Mg, Na, P and S) and the trace elements, Cu, Fe, Mn
and Zn. Plasma concentrations of the macro-elements were unchanged over
the treatment period and were not significantly different between the two
groups. However there was a significant effect of treatment (P<0.001) and
treatment x time interaction (P=0.024) on the Cu concentration in plasma.
After 7 days the Cu concentration in plasma of the LR3IGF-1 group
increased from 1.06±0.04 to 1.84±0.11 ug/mL compared with 0.94±0.07 and
1.27±0.08 ug/mL for the control group at 0 and 7 days respectively. This
difference continued for the remainder of the treatment period. Zinc
concentrations in plasma significantly (P<0.001) decreased in response to
LR3IGF-1 treatment (overall means: 0.83 and 0.69 mg/mL for the treatment
and control groups respectively; LSD, 0.06). Plasma Fe concentrations
declined with time, but there was no significant treatment effect. Within the
treatment group plasma Cu concentration was significantly (P<0.05)
correlated with concentration of endogenous IGF-1 and strongly negatively
correlated (P<0.001). These results suggest that chronic endocrine
imbalances, such as those imposed from the LR3IGF-1 treatment, may result
in changes to tissue distribution of trace elements. Such effects may result in
secondary complications. However, an increase in Cu availability for
nonhepatic tissue use may be beneficial, particularly in situations of mild,
chronic, Cu deficiency.
Keywords: NZSAPAB;
plasma; insulin-like growth factor-1; copper; zinc; ceruloplasmin;
sheep
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