ABSTRACT
Calcium is known to be involved in a multiplicity of cellular functions. Some of these include its role as a cofactor for enzyme activities, the regulation of secretory processes, the control of muscle cell activity, and the regulation of membrane transport phenomena. In the mammary gland, massive quantities of calcium are taken up from the plasma into the alveolar cells during lactation. Most of this calcium is then secreted into the milk, primarily associated with casein micelles. Calcium is also essential for prolactin to express its actions on a number of metabolic processes in mammary tissues. Removing calcium from the culture medium has been shown to abolish the effects of prolactin in mammary tissues on several metabolic processes, including RNA synthesis, casein synthesis, and triglyceride synthesis. Calmodulin is a cellular protein which combines with calcium and reduces the calcium ion concentration required to activate certain calcium-dependent enzymes.
