Flow and composition of afferent mammary gland lymph.

Afferent mammary lymphatic flow was characterized in conscious lactating cows during milking and prior to, during, and after intramammary infusion of endotoxins. Lymph flow (13 to 45 ml/h) was pulsatile with monophasic and multiphasic episodes. Flow resulted from 62 to 67 episodes per h. Episodes varied from 1 to 53 s in duration. Maximum instantaneous flow ranged from 163 to 245 microliters/s. Flow did not increase consistently during milking. Lymph flow increased (5.5- to 8-fold) during endotoxin-induced mastitis. Flow rates were elevated for up to 48 h after infusion of endotoxin. Compositional comparisons between afferent mammary lymph and blood plasma showed distinct differences. Lymph contained 7, 6, and 10 times less protein, albumin, and globulin, respectively, than did plasma. Glucose concentrations were equivalent. Lymph had 17 times less cholesterol and about one-half as much triglyceride and calcium as did plasma. gamma-Glutamyl-transaminase and aspartate transaminase were substantially higher in plasma than in lymph. Afferent mammary lymph has unique compositional characteristics. The lymph ducts contained an intrinsic mechanism for lymph movement. Moreover, this mechanism was altered by inflammation. The techniques herein provide a better understanding of the mammary lymphatic system.