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Tissue specific differences in insulin receptor characteristics in the mature bovine animal

Published online by Cambridge University Press:  05 November 2021

P.D. McGrattan
Affiliation:
The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland
A.R.G. Wylie
Affiliation:
The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, Northern Ireland
R.W.J. Steen
Affiliation:
Agricultural Research Institute of Northern Ireland, Hillsborough, Co. Down BT26 6DR, Northern Ireland
J. Nelson
Affiliation:
The Queen's University of Belfast, Medical Biology Centre, Belfast BT9 7BL, Northern Ireland
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Extract

Insulin is believed to play a key role in the partitioning of nutrients towards fat and protein deposition. The biological effects of insulin are a function of plasma insulin concentration, insulin-receptor concentration and the affinity of the receptor. The number and affinity of insulin receptors on adipocytes differs between genetically lean and obese pigs (Camara and Mourot, 1996) while receptor number, but not affinity, was shown to differ in a variety of bovine muscles (Boge et al., 1995). The objective of the current work was to determine if insulin receptor affinity and number vary between the principal target tissues (i.e. liver, muscle and adipose tissue) in the bovine animal.

Five Charolais-cross steers were offered grass silage ad libitum from 18 months of age until slaughter, at 701± 22.9 kg, at a commercial abattoir. Samples of liver [L], of two skeletal muscles [Ml, M3] and of subcutaneous [S], omental [0]and renal [R] fats were taken as soon as possible after slaughter (typically <30min for L, M3, S and O and <45min for Mland R), wrapped and snap frozen in liquid nitrogen prior to storage at -70 °. Insulin receptors were partially purified by solubilising tissues in 1% Triton X-100 for 24 hours at 4 °C followed by centrifugation (100000 x g, lh, 4°) and affinity chromatography of the supernatants on 0.5 ml wheatgerm agglutinin Sepharose 6MB columns. Bound receptors were eluted from the column with 0.3M N-acetyl-D-glucosamine. Receptor binding was assessed using a tracer amount of A-14 125I-insulin (∼35 pM) and increasing concentrations of unlabelled insulin (0-10 μM) in a total volume of 150 μl of pH 7.4 buffer as described by Magri et al (1990).

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Copyright
Copyright © British Society of Animal Science 1997

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References

Boge, A., Sauerwein, H. and Meyer, H.H.D. 1995. Experimental and Clinical Endocrinology and Diabetes 104: 101106.Google Scholar
Camara, M. and Mourot, J. 1996. Proceedings of the Nutrition Society 55: 66A.Google Scholar
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