In vitro study of the function of adrenocortical cells from pigs of differing in vivo response to adrenocorticotropin

Shu-Hua Zhang From the Department of Agriculture and Rural Affairs, Victoria, Veterinary Research Institute, Attwood, 475-485 Mickleham Rd, Attwood, Victoria 3049, Australia (Hennessy), and the School of Agriculture, La Trobe University, Bundoora, Victoria 3083, Australia (Zhang, Cranwell).

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 B Agr Sci
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David P. Hennessy From the Department of Agriculture and Rural Affairs, Victoria, Veterinary Research Institute, Attwood, 475-485 Mickleham Rd, Attwood, Victoria 3049, Australia (Hennessy), and the School of Agriculture, La Trobe University, Bundoora, Victoria 3083, Australia (Zhang, Cranwell).

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Peter D. Cranwell From the Department of Agriculture and Rural Affairs, Victoria, Veterinary Research Institute, Attwood, 475-485 Mickleham Rd, Attwood, Victoria 3049, Australia (Hennessy), and the School of Agriculture, La Trobe University, Bundoora, Victoria 3083, Australia (Zhang, Cranwell).

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SUMMARY

A study was conducted to determine whether within-breed differences in adrenocortical response to exogenous adrenocorticotropin (acth) might be accounted for by differences in responsiveness of the adrenocortical cells per se. Large White × Landrace male pigs (n = 20) were used; 10 had high adrenocortical response to acth administration and 10 had low response. Five high and 5 low responders were euthanatized at 15 weeks of age, and the remaining 5 high and 5 low responders were euthanatized at 21 weeks of age. Adrenal glands were removed and weighed, and adrenocortical cells were dispersed by tryptic digestion and incubated for 2 hours with synthetic acth at concentrations ranging from 0.5 to 10,000 pg/ml. Samples were taken at 30-minute intervals, and cortisol concentration was determined by use of a radioimmunoassay. Results indicate that for pigs of both age groups, high responders had heavier adrenal glands, with higher adrenocortical cell density and higher cell yield than did low responders. Synthetic acth had a stimulatory effect on dispersed porcine adrenocortical cells, as indicated by changes in cortisol concentration in vitro. Adrenocortical cells from high responders produced less cortisol, on a per-cell basis, than did those from low responders. However, when corrected for total cell yield, the potential cortisol production by each pair of adrenal glands was significantly (P < 0.05) higher in the high responders than in the low responders. Thus, high-responding pigs have larger adrenal glands and higher adrenocortical cell density, which may result in higher output of cortisol after acth administration or exposure to stressors.

For high- and low-responding groups, 15-week-old pigs had higher adrenal gland weight to body weight ratio, higher adrenocortical cell density, and higher steroidogenic function per adrenocortical cell than did 21-week-old pigs.

SUMMARY

A study was conducted to determine whether within-breed differences in adrenocortical response to exogenous adrenocorticotropin (acth) might be accounted for by differences in responsiveness of the adrenocortical cells per se. Large White × Landrace male pigs (n = 20) were used; 10 had high adrenocortical response to acth administration and 10 had low response. Five high and 5 low responders were euthanatized at 15 weeks of age, and the remaining 5 high and 5 low responders were euthanatized at 21 weeks of age. Adrenal glands were removed and weighed, and adrenocortical cells were dispersed by tryptic digestion and incubated for 2 hours with synthetic acth at concentrations ranging from 0.5 to 10,000 pg/ml. Samples were taken at 30-minute intervals, and cortisol concentration was determined by use of a radioimmunoassay. Results indicate that for pigs of both age groups, high responders had heavier adrenal glands, with higher adrenocortical cell density and higher cell yield than did low responders. Synthetic acth had a stimulatory effect on dispersed porcine adrenocortical cells, as indicated by changes in cortisol concentration in vitro. Adrenocortical cells from high responders produced less cortisol, on a per-cell basis, than did those from low responders. However, when corrected for total cell yield, the potential cortisol production by each pair of adrenal glands was significantly (P < 0.05) higher in the high responders than in the low responders. Thus, high-responding pigs have larger adrenal glands and higher adrenocortical cell density, which may result in higher output of cortisol after acth administration or exposure to stressors.

For high- and low-responding groups, 15-week-old pigs had higher adrenal gland weight to body weight ratio, higher adrenocortical cell density, and higher steroidogenic function per adrenocortical cell than did 21-week-old pigs.

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