Expression of parathyroid hormone-related protein (PTHrP) mRNA in mammary gland of periparturient cows

New concepts of breast cell communication to bone

Lactation is the most extreme case of normal physiological bone loss during a lifetime, and breast cancers have a strong tendency to metastasize to bone. In both the physiological and pathological circumstances, parathyroid hormone-related peptide (PTHrP) plays a central role. Until recently there were no regulatory mechanisms to explain the induction of endocrine PTHrP secretion from breast cells during lactation. The mammary epithelium possesses a local serotonin signaling system which drives PTHrP expression during lactation and in breast cancer cells. The mammary gland serotonin system is highly induced in response to alveolar dilation due to milk secretion. Discovery of serotonergic control of PTHrP suggests that it may be possible to manipulate the breast-to-bone axis by targeting serotonin signaling.

Immunolocalization of PTHrP in the parotid glands of three rodents species: Clethrionomys glareoulus, Microtus arvalis and white Swiss mice

The current study was inspired by the fact that since 2004 no report had appeared on the occurrence of this peptide in healthy parotid glands of humans and animals. The objective of the current study was to investigate the immunolocalization of PTHrP in the parotid gland of three male rodents: 6 common voles (Microtus arvalis, Pallas, 1779), 6 bank voles (Clethrionomys glareoulus, Schreber, 1780) and 6 white Swiss mice, as well as to find out any species differences in the distribution of this peptide in various types of cells of the parotid gland. Immunocytochemical reactions were performed using the ABC technique with specific rabbit antibodies against human PTHrP (34-53) (CALBIOCHEM), diluted 1:70 and 1:50. We observed positive PTHrP expression in the epithelial cells of the striated duct in all the three animal species. The expression was strong in white mouse and very strong in common vole and bank vole. In all the rodent species studied, the reaction for PTHrP was granular in nature and irregularly distributed in the cytoplasm, being definitely stronger at the base and weaker at the apex of the cells. The PTHrP expression was negative in the epithelium of the intercalated duct, interlobular duct, main excretory duct, as well as in the myoepithelial cells surrounding the excretory ducts or serous acini.

Expression of bovine parathyroid hormone/parathyroid hormone- related protein (PTH/PTHrP) receptor mRNA in the mammary gland of cows

To examine the PTH/PTHrP receptor in the mammary gland, molecular cloning of bovine PTH/PTHrP receptor and measurement of its mRNA expression were carried out in cows during the periparturient period. The PTH/PTHrP receptor gene was partially cloned, and expression of bovine PTH/PTHrP receptor mRNA was detected in various tissues of the cow. In the mammary gland, PTH/PTHrP receptor mRNA expression was constantly low during the periparturient period, whereas PTHrP mRNA expression dramatically increased after parturition. This suggested that expression of PTH/PTHrP receptor mRNA in the mammary gland is not affected by lactation in cows.

Parathyroid Hormone-Related Protein (PTHrP) and Ca Levels in the Milk of Lactating Cows

To investigate the roles of mammary PTHrP in calcium uptake and/or release in the mammary gland of cows, plasma PTHrP and Ca levels, and their arterial-venous differences were examined in a Jersey cow during the periparturient period. Levels of Ca in both abdominal aorta and abdominal subcutaneous vein blood slightly decreased around the parturition and at 24 days after the parturition, however, no remarkable arterial-venous differences were observed. Plasma PTHrP levels in both arterial and venous samples were below the detection limit (0.57 pmol/l) during the experimental period. Milk PTHrP and Ca levels were measured in 9 Holstein dairy cows. Although plasma PTHrP levels in all arterial and venous samples were also below the detection limit, milk PTHrP and Ca levels were remarkably high, ranging from 14,900 pmol/l to 41,200 pmol/l and from 772 mg/l to 1,200 mg/l, respectively. In addition, a significant positive correlation (P<0.01) was observed between milk PTHrP and Ca levels. These results suggested that mammary PTHrP is closely related to Ca concentration in the milk.