Endotoxin Induced Migration of Leukocytes from Blood to Milk

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Abstract
Guinea pigs were separated from young on days 5-7 of lactation. They were anesthetized with ether and were infused via the teat canal with sterile saline (0.5 ml) or Escherichia coli endotoxin (O26:B6:500 .mu.g/0.5 ml). Each animal served as its own control by having sterile saline in 1 gland and endotoxin in the other. Animals were sacrified 4, 6, 8, and 12 h later to determine the time of maximum migration of polymorphonuclear leukocytes (PMN) from blood to milk. A control group of animals having had no intramammary infusion was sacrificed. Tissues were prepared for observation by light microscopy and EM. Five fields/slide, 5 slides/animal, and 3 animals/period were examined by light microscopy, and numbers of PMN/field were categorized for presence in the capillary, in interstitial space, touching the basal lamina, between epithelial cells of an alveolus and in the lumen of an alveolus. PMN were in small numbers in the lumen by 4 h and peaked at .apprx. 8 h after intramammary infusion of endotoxin. By 12 h numbers had decreased. PMN were observed by EM in the intercellular spaces of the alveolar epithelium. A time sequence model using the guinea pig to study mechanisms of leukocyre migration into milk based upon tissue studies may be used in research aimed at controlling mastitis.

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