IL-8 mRNA expression in the mouse mammary glands during pregnancy and lactation

Interkeukin-8 (IL-8) is an important inflammatory mediator. It is an angiogenic factor associated with inflammation and carcinogenesis. To date, research on IL-8 has been limited to its role as an indicator of inflammation. There has been no systematic research concerning IL-8 expression levels in the mouse mammary gland during pregnancy and lactation. Mouse mammary gland samples were collected on days 1, 6, 12, 18 of pregnancy and of lactation (6 mice per group). The expression levels of IL-8 mRNA were measured by semi-quantitative RT-PCR, with GAPDH as an internal control. IL-8 mRNA was highly expressed on day 1 of pregnancy in the mouse mammary glands (IL-8(IOD)/GAPDH(IOD) = 1.68), and then suddenly declined; it reached 0.74 and 0.71 on days 6 and 12 of pregnancy. On day 18 of pregnancy, it started to increase (IL-8(IOD)/GAPDH(IOD) = 1.02). However, the expression levels of IL-8 mRNA were not significant during pregnancy. During lactation, IL-8 expression level was lower than during pregnancy, but it stabilized at 0.32-0.41 (IL-8(IOD)/GAPDH(IOD)) from day 1 to day 18 of lactation, although the difference was not significant. We suggest that the changes in IL-8 expression level during development is related to its regulatory role in mouse mammary gland immunity.