Preliminary 'in vivo' measurements of protein and energy metabolism in the skin of sheep

Abstract

An arterio-venous preparation was developed which allowed infusion into, and/or sampling from, branches of the deep circumflex iliac artery and vein supplying and draining a discrete area of skin on the abdominal flank of Romney sheep.Measurements of blood flow (using dye dilution techniques), utilization or output of energy metabolites (oxygen, glucose, lactate and acetate) and amino acid metabolism were made in relation to whole body protein and energy metabolism.Measurements on the patch suggested that blood flow to the total skin was about 6% of cardiac output but that only 1-2% of whole body oxygen utilization occurred in the skin. This was partly accounted for by a significant proportion of glucose uptake (1.15 g day-1) being anaerobically oxidized to lactate (0.41 g day-1). Measurements of protein synthesis in the patch showed that between 10 and 16% of whole body protein synthesis occurs in the skin.Results from the preparation demonstrate that it is a useful procedure to study metabolism in a defined patch of skin in the intact animal.

A comparison of changes in whole body and skin amino acid metabolism of sheep in response to 24 h continuous infusions of variants of insulin-like growth factor 1

“…Polyvinylchloride catheters were then implanted under fluothane anaesthesia into the descending lateral branches of the deep circumflex iliac artery (A1) and vein (V) on one side of each sheep as described previously (Harris et al 1989). This surgical preparation allows both local infusion and sampling from a discrete patch of skin on the lateral abdominal flank of the sheep.…”

Metabolic response of sheep skin to a chronic infusion of a variant of insulin-like growth factor I

“…Glucose and lactate concentrations were measured enzymically as described previously [16]. Cysteine concentration was determined by a modified automated method using acid ninhydrin [17].…”

“…The sample was frozen at -85°C before analysis. Blood (1 ml) for glucose and lactate analysis was precipitated with 1 ml of perchloroacetic acid (0.6 M), and the supernatant neutralized with 3 M KOH (about 60 ,l) before freezing at -85°C [16]. Blood for measurement of amino acid concentration and phenylalanine specific radioactivity (1 ml) was mixed with 0.5 ml of 30 % trichloroacetic acid containing 200,uM norleucine as an internal standard, vortexed and centrifuged at 4 'C.…”

“…MATERIALS AND METHODS Animals and surgical preparation Twelve 1-year-old castrated Romney sheep (30-35 kg) had finebore poly(vinyl chloride) catheters implanted, under fluothane anaesthesia, into the descending lateral branches of the deep circumflex iliac artery (Al) and vein (V) of the left side (LAI and LV) and right side (RA1 and RV) of each sheep as described previously [16]. This surgical preparation allows infusion into, and sampling of the venous drainage from, a discrete patch of skin on the lateral abdominal flank of the sheep.…”

“…At 4 days after surgery the surgical patches were assessed for patency [16], and sheep with two patent sides were allocated to LR31GF-I infusion and those with only one patent side were allocated to be independent controls. In the six sheep allocated to LR3IGF-I treatment, one venous catheter failed to sample past the preinfusion period and so no metabolic measurements were made.…”