EFFECTS OF LYSINE AND HORMONES ON AMINO-ACID CONCENTRATION IN THE SKIN OF ANGORA-GOATS

The effects of lysine and hormones on amino acid and glucose venous ou tflow in the skin and the whole body were determined in Angora wethers (n = 5). The goats had chronically catheterized superficial branches of the deep circumflex iliac artery and vein of each side. Four experi ments involved the intra-arterial test infusion on one side (60 min) o f lysine (0, 0.16, 0.8 and 4mgh(-1); Experiment I) alone and lysine (4 mgh(-1)) together with infusions (60min) of successively increasing do ses of insulin (0, 0.1, 1 and 10mUh(-1); Experiment 2), cortisol (0, 0 .15, 1.5 and 15 mu gh(-1); Experiment 3), and triiodothyronine (T-3), 0, 0.02, 0.2 and 2 mu gh(-1); Experiment 4). The other side served as control and was infused with saline only (10mlh(-1)). Lysine concentra tions in venous outflow from the control side (80.9 mu M) were unaffec ted by lysine infusion, whereas venous lysine concentrations in the te st side were 82.1, 85.7, 96.9 and 109 mu M during lysine infusion at 0 mgh(-1), 0.16mgh(-1), 0.8 mgh(-1) and 4mg h(-1), respectively. Althoug h venous concentrations of insulin (approximately 22 mu U ml(-1)) were similar (P > 0.05) and unchanged in both sides for all doses of insul in infused, the highest dose of insulin infusion (10 mu Uh(-1)) decrea sed (P < 0.01) lysine and glucose venous concentrations in the skin. P lasma variables were unaffected (P > 0.05) by cortisol despite six- to ten-fold increase in the plasma cortisol concentration. The highest d ose of T-3 (2 mu gh(-1)) increased (P < 0.02) T-3 from 250 to 450ngdl( -1), decreased (P < 0.01) plasma concentrations of the branched-chain amino acids (BCAA) by approximately 20-30% and phenylalanine concentra tions by 80%, and increased (P < 0.01) glucose concentrations by 36% e qually in venous plasma in both perfused regions. These results sugges t that whole body BCAA and glucose concentrations in Angora goats are highly responsive to doubling of physiological concentrations of T-3, but apparently unresponsive to acute (60min) pharmacological increment s in plasma cortisol concentrations. Knowledge of the interaction betw een nutrients and hormones in the skin will allow better ration formul ation and development of local growth promotants.