Mechanism of zinc homeostasis.

Homeostatic equilibrium of a nutrient is characteristic of a healthy body. For zinc, phytate has been shown to alter that equilibrium in several monogastric species including man. The pancreas is an important organ in the maintenance of zinc homeostasis. Elevated calcium has been shown to be a synergistic agent in affecting the rate of onset and rate of homeostatic change. In the studies described, rats were depleted of zinc to differing extents, zinc was injected intraperitoneally to label the endogenous zinc pool. Phytate- and nonphytate-containing protein diets were fed and feces were collected. Feces were counted for radioactivity. The ratios of radioactivity (phytate:nonphytate) indicated that the major effect of phytate was on the endogenous secreted pool. Evidence is included to indicate that two, pancreatic labile pools of zinc are secreted, one is stable complexes not affected by phytate and two, a labile pool of zinc readily available for complexation. A mathematical model is included that fits all nutritional models for zinc homeostasis.