Calcium lysosomes in rachitic and vitamin D3 replete chick duodenal absorptive cells

Calcium-containing lysomes were described in a previous communication in this series (Davis et al., 1979). Their potential role in intestinal calcium uptake and transcellular transports was hypothesized. To further this notion, the effects of a rachitogenic diet and vitamin D3 repletion were investigated. Intestinal absorptive cells from chicks maintained on a vitamin D deficient diet were characterized by decreased numbers of supranuclear calcium lysosomes. In contrast, intestinal cells from chicks given vitamin D3 (cholecalciferol) subsequent to the rachitogenic diet showed numerous large compound supranuclear calcium lysosomes. Since other steroid hormones are known to effect lysosomes, it is tempting to speculate that vitamin D, itself a steroid hormone, may activate lysosomes which themselves might be involved in calcium homeostatic mechanisms.