Parathyroid hormone-related protein: a regulated calcium-mobilizing product of the mammary gland.
Parathyroid hormone-related protein shares similarities in sequence and function with the endocrine hormone, parathyroid hormone. However, unlike parathyroid hormone, a product of the parathyroid glands, parathyroid hormone-related protein has a wide distribution in tissues, including the mammary gland. Although during pregnancy the expression of parathyroid hormone-related protein in the mammary gland is low, following birth, protein levels rise sharply in the gland in response to elevations in serum prolactin. Large amounts of parathyroid hormone-related protein are secreted into milk, suggesting a possible role in the neonate. Transient phosphaturia and elevations of parathyroid hormone-related protein in mammary vein plasma support a possible endocrine function for parathyroid hormone-related protein during lactation. Recent evidence suggests a local function for parathyroid hormone-related protein in the lactating mammary gland, and evidence exists that parathyroid hormone-related protein stimulates calcium secretion by the goat mammary gland. Parathyroid hormone-related protein, a putative vasodilator, is produced by the external nutrient vasculature of the mammary gland, and levels within this tissue are regulated during lactation. Infusion of parathyroid hormone-related protein into the ovine mammary artery increases gland blood flow, suggesting a role for the protein in modulation of mammary gland hemodynamics. Regulation of parathyroid hormone-related protein synthesis by the lactating gland, together with the protein's actions on regional blood flow and calcium secretion, support an important function in the mammary gland during lactogenesis.
Thiede
M A
MA
Pfizer Central Research, Groton, CT 06340.
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D007774:Lactation; D008321:Mammary Glands, Animal / Q000098:blood supply / Q000378:metabolism*; D008969:Molecular Sequence Data; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000737:chemistry / Q000502:physiology*; D017385:Sequence Homology
C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D002118:Calcium