Measurement of blood flow and metabolite uptake by the skin of fleeceweight-selected and control Romney rams

Abstract

Ten, 2 to 3 year old Romney rams (50-60 kg), five from the Massey University Fleeceweight Selection line (FW) and five from the Control line (C) had catheters implanted into the arterial supply and venous drainage of a patch of abdominal flank skin. A further catheter was implanted into the saphenous artery. Infusions of radio-labelled cysteine or glucose were given into the skin artery together with infusions of paraamino hippuric acid for measurement of blood flow by dye dilution. Five sheep (2FW and 3C) also had infusions of radio-labelled glutathione. During arterio/venous difference procedures, measurements were made of oxygen, cysteine, glucose and glutathione uptake, together with lactate production, by the skin. Wool production from the catheterised patch of skin was also measured. There were no significant differences found between the FW and C sheep in any parameter measured except glutathione concentration (FW = 911¦39 8M; C = 789¦28 8M) and, because of the low numbers of animals, only a trend for wool production (P = 0.06) to be greater in the FW sheep. When results from the two flocks were combined, cysteine flux per weight of skin (P = 0.04), the percentage uptake of 35SS-cysteine (P = 0.004) and the rate of cysteine utilization for protein synthesis per weight (P = 0.013) or area P 0.009) of skin were significantly related to wool production. The percentage uptake of 35S-glutathione was also significantly related to wool production (P = 0.013). However, blood flow, cysteine concentration in the blood and cysteine flux per area of skin were not significantly related to wool production. The results suggest that although nutrient supply, especially of cysteine to the skin is obviously important in wool production, it is not only the flux of nutrient itself which is critical but the rate of uptake (transport) of that nutrient by the cells of the skin which is enhanced in high wool producing sheep.