Abstract: Male Kazak sheep and Xinjiang fine wool sheep from 2 to 120-day-old were selected to investigate the developmental changes and effect on Intramuscular fat (IMF) content of lipoprotein lipase (LPL) mRNA expression in sheep muscle. Six sheep of each breed (only Xinjiang fine wool sheep at 120-day-old) were slaughtered at 2, 30, 60, 90, 120 days respectively to sample longissimus dorsi muscle to analyze the IMF content. The total RNA of the samples was extracted to determine the developmental changes of LPL mRNA expression levels by Real time PCR .The results showed that: (1) In male Kazak sheep, the IMF content increased continuously with growing and showed significant difference (P<0.05) between ages, but no difference between ages existed in Xinjiang fine wool sheep (P<0.05). Furthermore, the IMF content of male Kazak sheep was extremely higher (P<0.01) than that of Xinjiang fine wool sheep from 30 to 90 day. (2) LPL mRNA expression level was the highest at 2 day and showed extremely higher than other ages (P<0.01) in male Kazak sheep, it was the lowest at 60 day and then increased. In Xinjiang fine wool sheep, the LPL mRNA was the highest at 30 day (P<0.01), then decreased continuously and to the lowest lever at 90 day; then, the LPL mRNA increased once more. (3) In male Kazak sheep, from 2to 60 day, LPL mRNA expression level was negatively related to IMF content (γ = -0.625, P<0.05), and there was no obviously relationship between LPL and the male Xinjiang fine wool sheep.

Key words: sheep, Intamuscular fat, lipoprotein lipase, Real time PCR