Physiological Control of Mammary Growth, Lactogenesis, and Lactation

Abstract

Research since 1955 that contributed to understanding mammary function was reviewed. Technical breakthroughs included methods: 1) to quantify mammary growth; 2) to visualize organelles in cells; 3) to grow and maintain mammary tissue in vitro; 4) to quantify hormones in blood; and 5) to determine binding affinities and numbers of binding sites for hormones. Physiological discoveries included 1) mammary cells accumulate throughout pregnancy and early lactation; 2) high doses of estradiol-17β and progesterone induce substantial milk production in a majority of cattle; 3) estradiol-17β, progesterone, prolactin, growth hormone, and placental lactogen synergize to stimulate mammary growth; 4) prolactin and glucocorticoids induce and progesterone blocks lactogenesis; 5) milking induces release of prolactin, glucocorticoids, and oxytocin into blood; 6) growth hormone is galactopoietic in ruminants; 7) progesterone concentrations in milk may be used to diagnose pregnancy; and 8) receptors for estrogens, progesterone, glucocorticoids, prolactin, placental lactogen, insulin, and oxytocin are in mammary tissue. Areas that seem likely to provide new methods for regulation of milk production efficiency are molecular biology, hormone receptors, harvesting milk, endocrine-nutrient metabolism, genetic and environmental basis of hormonal control of lactation. With continued support of research, generation of information on physiological control of the mammary gland and commercial application of this knowledge should proceed rapidly in an exciting future!