Effects of extracellular Ca2+ on phagocytosis and intracellular Ca2+ concentrations in polymorphonuclear leukocytes of postpartum dairy cows

The aim of this study was to determine the effects of extracellular Ca2+ concentration ([Ca2+](e)) on phagocytosis and intracellular Ca2+. concentration ([Ca2+](i)) in bovine polymorphonuclear leukocytes (PMNs). The experiments were performed by using blood samples from parturient paretic and clinically normal parturient cows and manipulating the [Ca2+](e) in vitro. Phagocytosis by PMNs (with and without stimulation with phorbol myristate acetate and inhibition with cytochalasin B) and resting [Ca2+](i) were significantly lower in parturient paretic cows. Repletion of Ca2+ in the extracellular media for the samples from these animals increased phagocytosis and resting [Ca2+](i). In the blood of clinically normal parturient cows, decreasing the [Ca2+](e) decreased phagocytosis and resting [Ca2+](i) in PMNs, but increasing the [Ca2+](e) did not affect phagocytosis. These results suggest that the hypocalcemic condition of parturient paretic cows in vivo causes decreased phagocytosis and resting [Ca2+](i) in PMNs, which may partly contribute to greater susceptibility to infection. (C) 2003 Elsevier Science Ltd. All rights reserved.