Tissue components of the domestic fowl. 4. Plasma-alkaline-phosphatase activity

Abstract

A simple and flexible method is described for assessing plasma-alkaline-phosphatase activity against 4-nitrophenyl phosphate. It has been compared with the Bodansky and the King-Armstrong procedures. Both adult non-laying hens and cocks show enzymic activity of the same order. The plasmas of immature birds (5-6 weeks old) of both sexes have alkaline-phosphatase levels up to 10 times those found in non-laying adults. At 8 1/2-10 weeks of age great irregularities may be found in that the plasma-alkaline-phosphatase activity of an individual may have dropped to a level near that of the adults, although these birds continue to grow at the same rate as those of 5-6 weeks. In the hen, the average level of plasma enzymic acitivity is increased by about 50% upon the bird coming into lay, when wide fluctuations become apparent. The lowest levels in the laying hen are, however, of the same order as those found in the non-laying bird and in the cock. In some hens a fairly steady level of activity with small fluctuations is attained after the first 2 months of intensive egg production. Other birds, however, continue to show very large fluctuations in alkaline-phosphatase activity with no apparent tendency to the establishment of homeostasis with respect to this enzyme. The massive temporary increases in plasma phosphatase shown by the laying hen are believed to reflect a stimulation of the osteoblastic recalcification process called into action by the drain on skeletal calcium required for egg shells.