A COMPARATIVE-STUDY OF THE IN-VITRO ACTIVITIES OF 3 ENZYMES NA-TRIPHOSPHATE, GAMMA-GLUTAMYL-TRANSPEPTIDASE, AND ORNITHINE DECARBOXYLASE IN SKIN SAMPLED FROM MERINO SHEEP WITH DIFFERENT CAPACITIES FOR WOOL GROWTH(, K+ ADENOSINE)

The concentration of sodium, potassium adenosine triphosphatase, and t he in vitro activities of gamma-glutamyl transpeptidase and ornithine decarboxylase, were studied in skin from Merino sheep to determine whe ther these traits differed in skin from sheep whose rate of wool produ ction was influenced by genetic and dietary factors. Sheep from 2 floc ks were compared, these being selectively bred for high (Fl+') or low (Fl-') clean fleece weight per head. The sheep were given one of 2 pel leted rations (L and H). The L ration provided metabolisable energy ap proximately equal to 0.75 times maintenance. The H ration provided app roximately twice maintenance, and this ration had a higher protein con tent due to the inclusion of formaldehyde-protected casein. Eight shee p were studied in each flock at each dietary level. The average concen tration of sodium, potassium adenosine triphosphatase, measured by H-3 ouabain binding, was 132 pmol/g air-dry skin (s.e.d. = +/-30). The ac tivity of gamma-glutamyl transpeptidase was 0.69 mu mol product/h . mg protein from skin (s.e.d. = +/-0.17). The average activity of ornithi ne decarboxylase in skin was 6.0 nmol carbon dioxide released/h . g sk in (s.e.d. = +/-1.2). Plucking of fibres from the skin 4 h before samp ling resulted in an increase (P < 0.05) in the activity of ornithine d ecarboxylase to 12.9 nmol carbon dioxide/h . g skin. For each of the e nzymes, the measured values tended to be greater in the skin of sheep from the genetically high-producing flock and in skin from sheep on th e H ration, but none of these differences was statistically significan t.