The levels of N-acetyl-β-glucosaminidase (NAGase) and acid phosphatase were analysed in tissue from the teat and lactiferous sinus epithelia of dairy cows at different stages of lactation. Enzyme levels were lower in the epithelia of the teat sinus than of the lactiferous sinus. For both enzymes, levels were highest in tissue from post-partum glands, lowest in those from dry and mid-lactation glands. In involuting glands the levels were high, but not as high as the post-partum glands.
Mattila, T., O'Boyle, D., & Frost, A. (1988). Distribution of lysosomal enzymes within the non-secretory epithelium of the bovine mammary gland. Journal of Dairy Research, 55(3), 339-344. https://doi.org/10.1017/S0022029900028594