AJP - Regulatory, Integrative and Comparative Physiology, Vol 269, Issue 4 848-R855, Copyright © 1995 by American Physiological Society

ARTICLES

EGTA-induced disruption of epithelial cell tight junctions in the lactating caprine mammary gland

K. Stelwagen, V. C. Farr, S. R. Davis and C. G. Prosser
AgResearch, Ruakura Research Centre, Hamilton, New Zealand.

The suitability of the Ca2+ chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) to induce disruption of mammary tight junctions (TJ) and its effect on milk secretion were investigated in six goats. EGTA was administered via the teat of one gland as an isosmotic (300 mosmol/l) K-EGTA solution (68 mM EGTA), whereas the control gland received an isosmotic sucrose solution. Lactose, Na, K, and Cl in milk, blood lactose, and the presence of Evans blue (EB) in mammary lymph were used as indicators of TJ disruption. EGTA caused transient (approximately 60 h) changes (P < 0.05) in the concentration of lactose, K, Na, and Cl in milk, consistent with loss of TJ integrity. This was confirmed by a rapid (< 1 h) increase (P < 0.05) in blood lactose levels. Moreover, EB appeared in lymph < 1 h after EGTA+EB treatment. Milk secretion declined unilaterally by 15% (P < 0.05) after EGTA and did not return to baseline until approximately 60 h after EGTA. EGTA caused a unilateral, temporary (first 7 h) increase in mammary blood flow. This study shows that a rapid temporary disruption of mammary TJ can be successfully induced in vivo and that such disruption compromises milk secretion.

This article has been cited by other articles:

				D. B. Shennan and M. Peaker Transport of Milk Constituents by the Mammary Gland Physiol Rev, July 1, 2000; 80(3): 925 - 951. [Abstract] [Full Text] [PDF]