Animal Science Abstract
The effects of intradermal injections of spermidine on the growth rate of fibres and mitosis of wool follicles in Merino lambs
S. M. Liu1,A, A. Murray1, A. C. Schlink1, G. Mata1 and D. G. Masters1
AE-mail: Shimin.Liu@CSIRO.au
1CSIRO Livestock Industries, Private Bag 5, Wembley, WA 6913, AustraliaAbstract
Polyamines (putrescine, spermidine and spermine) are required for optimal growth in all cells, and are essential for cell proliferation and growth of cultured wool follicles, with an optimal concentration of spermidine required for the fibre elongation. The effects of a local supply of exogenous spermidine on the rate of cell division in the wool follicles, the length growth rate and diameter of fibres were therefore examined in Merino lambs. Three groups of eight lambs (40 kg) were given food at 1•2 × maintenance. Spermidine was injected intradermally into a small patch (3 × 3 cm) on the left flank three times per day for 7 days at one of three concentrations: 1•38, 2•75 or 4•58 mmol in 0•8 ml volume. The same volume of saline was injected into the contralateral side as a control. The concentration of spermidine in the skin patch 3 h after injection on day 7 increased by proportionately 0•18, 0•33 or 0•41 (P < 0•001) respectively. The rates of cell division in the follicle bulb 3 h after the spermidine injection were proportionately 0•104, 0•184 and 0•283 higher compared with the contralateral side (P = 0•078 overall) for the low, medium and high doses of spermidine respectively and differed between the three doses (P < 0•05). The fibre length growth rate, as measured using autoradiography, was proportionately 0•099, 0•117 and 0•156 higher than that of the contralateral side (P < 0•001 overall) for the low, medium and high doses of spermidine respectively, but differences between doses were not significant (P > 0•05). Spermidine injection did not result in a significant change in fibre diameter during the treatment period. The ratio of fibre length growth rate to fibre diameter was increased by the injection of spermidine (P < 0•001). The results suggest that injecting extra spermidine into the skin altered spermidine homeostasis in the skin, stimulated cell proliferation and resulted in increased fibre growth.
Keywords: methionine, polyamines, sheep, spermidine, wool
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