Calcitonin Secretion by Human Placental Tissue

Abstract

We have investigated the synthesis in vitro of calcitonin (CT) by human placenta at term. Separate placental tissue samples were incubated in culture medium with various Ca concentrations for 6 h. The CT concentrations in the medium were determined by radio-immunoassay. In addition the effect of DB-cAMP on the synthesis was also studied. We could demonstrate CT secretion in all experiments. The CT concentrations were determined by two different antibodies. Both antibodies registered the CT secretion. Addition of DB-cAMP to the culture medium stimulates the synthesis.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery

“…The thyroid C-cells are often assumed to be the only site of calcitonin synthesis, but the breast and placenta become significant production sites during pregnancy (52,131). This has been most clearly demonstrated in women who have previously undergone a total thyroidectomy.…”

“…In one report a thyroidectomized woman nursing twins experienced multiple vertebral compression fractures and had marked bone loss confirmed by DXA; the authors speculated that calcitonin deficiency was to blame (811). But thyroidectomized women are not expected to be calcitonin deficient while breastfeeding because calcitonin produced by breast tissue leads to normal circulating calcitonin levels (52,131,755).…”

Fetal Control of Calcium Transport across the Rat Placenta

“…There have been few direct studies in other species (4) although fetal calcium homeostasis also appears to be autonomous in the rat. Thus PTH (5) and calcitonin (6) do not appear to cross the rat placenta and are presumably of fetal or placental (7,8) origin, and the fetal parathyroids (9) and thyroid "C" cells (10) are active in utero. Fetal 1,25(OH)2D3 may be derived from the mother across the placenta (1 l), be produced by the placenta itself (l2), or by the fetal kidney (1 3), although the fall in plasma 1 ,25(OH)2D3 concentration after bilateral nephrectomy of the sheep fetus (14) suggests thatjn this species the fetal kidney is the major source.…”

Bone Development and Mineral Homeostasis in the Fetus and Neonate: Roles of the Calciotropic and Phosphotropic Hormones

“…Rodent placentas also contain the intraplacental yolk sac, a bilayered membrane formed when part of the yolk sac becomes enfolded within the placenta; it is positioned directly between fetal and maternal blood vessels (FIGURE 6) (166,167,289). This structure shows more intense expression of many calciotropic genes compared with the surrounding trophoblasts, including calbindin-D 9k , Ca 2ϩ -ATPase, PTHrP, PTH1R, TRPV6, vitamin D receptor, calcitonin, calcitonin receptor, and CaSR (35,63,81,83,84,95,150,151,293,337,338,356,423,471,608,656,659). Its location between the maternal and fetal vessels is optimal for it to be a site of maternal-fetal calcium and other nutrient transport, independent of the trophoblast labyrinth (330,337,659).…”

“…The trophoblasts express numerous calciotropic and phosphotropic genes including calbindin-D 9k , Ca 2ϩ -ATPase (isoforms 1 and 4), and TRPV6 (63,95,273), PTHrP (82,162,184), PTH1R (82,183), CaSR (69), VDR (664), 1␣-hydroxylase (156,728,758), calcitonin (35), calcitonin receptor (356,471), and Klotho (483). C) SUMMARY OF KEY POINTS.…”