Chronic effects of recombinant porcine growth hormone on adrenal weight and activity in pigs.

This study was conducted to examine serum cortisol concentrations and adrenal cortisol output in pigs treated chronically with recombinant pGH (rpGH) at a maximally effective anabolic dose. Recombinant pGH (140 micrograms/kg body weight) was administered daily to eight barrows for 77 d. At slaughter, adrenal glands were removed, weighed and sliced; slices of fresh adrenal tissue were incubated for 1 h in the presence or absence of ACTH. Recombinant pGH increased adrenal weight by 39%. This change was accompanied by an inversely proportional reduction of in vitro cortisol output per gram of tissue, with the net result that total cortisol output per adrenal per kilogram of BW was unaltered, as was cortisol output in the presence of ACTH. Serum cortisol concentrations were measured in 10 barrows fitted with femoral artery catheters and treated daily with 0 or 140 micrograms rpGH/kg BW for 8 d. Basal and ACTH-stimulated cortisol concentrations were not altered by rpGH treatment. These results do not support our earlier speculation that a pGH-dependent increase in adrenal weight is associated with a chronic increase in adrenal activity, but rather demonstrate that corticosteroid output is tightly regulated and remains constant despite a marked increase in the size of the adrenal glands.