Effects of extracellular Ca2+ on phagocytosis and intracellular Ca2+ concentrations in polymorphonuclear leukocytes of postpartum dairy cows
2003
Ducusin, R.J.T. | Uzuka, Y. | Satoh, E. | Otani, M. | Nishimura, M. | Tanabe, S. | Sarashina, T.
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.
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