Measurement of parathyroid hormone-related protein in extracts of fetal parathyroid glands and placental membranes

Abbas, S. K.; Pickard, D. W.; Illingworth, Doreen V.; Storer, John B.; Purdie, David W; Moniz, Caje; Dixit, Mehul; Caple, I. W.; Ebeling, PR; Rodda, Christine; Martin, T. J.; Care, A. D.

doi:10.1677/joe.0.1240319

Cited by 70 publications

(23 citation statements)

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“…PTHrP-like activity has been localized in early placen ta in sheep and also in fetal sheep parathyroids [6,8]. More recently, PTHrP immunoreactivity has been identi fied in the parathyroid of a 7-week-old human fetus [20], Immunoreactive C-PTHrP was higher in cord blood than in maternal blood.…”

Section: Discussionmentioning

confidence: 99%

Parathyroid Hormone-Related Protein during Pregnancy and the Perinatal Period

Seki

Wada

Nagata

et al. 1994

Gynecol Obstet Invest

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To evaluate whether parathyroid hormone-related protein (PTHrP) plays any role in calcium metabolism during pregnancy and the perinatal period, we measured parathyroid hormone (PTH), immunoreactive PTHrP and calcium in maternal serum of women during pregnancy and puerperium, and in maternal and cord serum at delivery. Serum PTH levels in pregnant women were lower than those in nonpregnant women (p < 0.01). However, serum PTHrP levels were similar in the two groups of women. Cord serum total and ionic calcium levels were higher, and cord serum PTH levels were lower compared to maternal values (p < 0.01). Cord serum PTHrP levels were higher than maternal values, and umbilical arterial levels were higher than umbilical venous levels (p < 0.01). Higher levels of PTHrP in umbilical arterial blood than in umbilical venous blood suggest that the main source of cord blood PTHrP may be the fetus. PTHrP is reported to stimulate placental calcium transfer from mother to fetus in animals. The elevated cord blood PTHrP level in association with the decreased PTH level suggests that stimulation of placental calcium transfer by PTHrP may also be operative in humans.

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Section: Discussionmentioning

confidence: 99%

Parathyroid Hormone-Related Protein during Pregnancy and the Perinatal Period

Seki

Wada

Nagata

et al. 1994

Gynecol Obstet Invest

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“…Several fetal tissues in different species can synthesize PTHrP, including parathyroid, placental membranes (45,46), and liver (47). Suggestively, human fetuses and patients with humoral hypercalcemia of malignancy do share certain biochemical features, viz.…”

Section: Discussionmentioning

confidence: 99%

Circulating Levels of Biologically Active and Immunoreactive Intact Parathyroid Hormone in Human Newborns

et al. 1991

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ABSTRACT. We evaluated circulating levels of biologically active and immunoreactive intact parathyroid hormone in 47 newborns at birth and eight hypocalcemic preterm infants during the first 10 d of life. Use of two sensitive detection systems, the cytochemical bioassay and an immunoradiometric assay specific for intact parathyroid hormone, enabled us to compare plasma concentrations of PTH-like bioactivity (bioPTH) and iPTH-(1-84). Mean umbilical venous plasma bioPTH was elevated in nondiabetic term and preterm newborns [22.5 + 3.1 (fSEM) and 15.8 f 2.5 ng-equiv/L, respectively] compared with normal adult subjects (9.8 2 2.6 ng-equiv/ L; p < 0.01). Umbilical bioPTH was suppressed in five term infants of diabetic mothers (2.6 f 0.4 ng-equiv/L). In contrast, iPTH-(1-84) was low in term and preterm nondiabetic infants' and term infants of diabetic mothers' umbilical samples (5.4 f 1.5, 4.3 ' . 1.5, and 2.4 + 1.0 ng/ L, respectively). Umbilical venous bioPTH was highly correlated with the magnitude of the transplacental calcium gradient (r = 0.90; p < 0.05). In eight preterm infants studied longitudinally, by 24-36 h of life, declining plasma total and ionized calcium (1.71 f 0.04 and 0.78 f 0.03 mmol/L, respectively) were accompanied by a significant rise in both bioPTH (41.2 f 6.3 ng-equiv/L) and iPTH-(1-84) (56.3 f 11.6 ng/L). These data indicate that the 3rd trimester fetoplacental circulation contains levels of bioPTH several-fold higher than those of immunoreactive intact hormone. We also conclude that even hypocalcemic preterm newborn infants can significantly elevate circulating levels of FTH. (Pediatr Res 29: 201-207,1991) Abbreviations PTH, parathyroid hormone iPTH-(1-84), immunoreactive intact parathyroid hormone bioPTH, parathyroid hormone-like biologic activity IDM, infant of a diabetic mother Can total calcium concentration Ca,, ionized calcium concentration CBA, cytochemical bioassay G6PD, glucose 6-phosphate dehydrogenase DCT, distal convoluted tubule PTHrP, parathyroid hormone-related peptide Received June 14, 1990; accepted October 2, 1990. In humans and other mammals, the extracellular total and ionized calcium concentrations change dynamically during the transition from fetal to extrauterine life. The fetal circulation of mammals in the 3rd trimester is hypercalcemic relative to that of the mother. In humans, cessation of transplacental flow of calcium at birth is associated with decrements in CaT and Ca, concentrations. Blood calcium stabilizes I to 2 d after birth, then rises progressively to levels observed in older children and adults. An exaggeration of this sequence of events, early neonatal hypocalcemia (CaT < 1.75 mmol/L; <7.0 mg/dL), occurs in at least 35 to 50% of preterm newborn infants ( l , 2 ) and more than 90% of extremely preterm infants (3).Inference from other hypercalcemic states has suggested that the chronic hypercalcemia of late fetal existence might suppress fetal PTH secretion (4) and that neonatal parathyroid suppression might persist for several days postpartum, ...

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“…Numerous tissue sources may contribute to the circulating concentration of PTHrP, because in the embryo and fetus the gene is expressed by skeletal growth plates (299,365), cardiac and vascular smooth muscle (89), trophoblasts (5,336,602), intraplacental yolk sac (336), amnion (68,184), chorion (68), umbilical cord (185), and numerous other tissues and cell types. Venous umbilical PTHrP levels are higher than umbilical arterial levels in pigs, which suggests that the placenta may be an important source of circulating PTHrP in the fetus (7).…”

Section: Pthrpmentioning

confidence: 99%

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

Kovacs

2014

Physiological Reviews

207

188

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Mineral and bone metabolism are regulated differently in utero compared with the adult. The fetal kidneys, intestines, and skeleton are not dominant sources of mineral supply for the fetus. Instead, the placenta meets the fetal need for mineral by actively transporting calcium, phosphorus, and magnesium from the maternal circulation. These minerals are maintained in the fetal circulation at higher concentrations than in the mother and normal adult, and such high levels appear necessary for the developing skeleton to accrete a normal amount of mineral by term. Parathyroid hormone (PTH) and calcitriol circulate at low concentrations in the fetal circulation. Fetal bone development and the regulation of serum minerals are critically dependent on PTH and PTH-related protein, but not vitamin D/calcitriol, fibroblast growth factor-23, calcitonin, or the sex steroids. After birth, the serum calcium falls and phosphorus rises before gradually reaching adult values over the subsequent 24 -48 h. The intestines are the main source of mineral for the neonate, while the kidneys reabsorb mineral, and bone turnover contributes mineral to the circulation. This switch in the regulation of mineral homeostasis is triggered by loss of the placenta and a postnatal fall in serum calcium, and is followed in sequence by a rise in PTH and then an increase in calcitriol. Intestinal calcium absorption is initially a passive process facilitated by lactose, but later becomes active and calcitriol-dependent. However, calcitriol's role can be bypassed by increasing the calcium content of the diet, or by parenteral administration of calcium.

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Measurement of parathyroid hormone-related protein in extracts of fetal parathyroid glands and placental membranes

Cited by 70 publications

References 10 publications

Parathyroid Hormone-Related Protein during Pregnancy and the Perinatal Period

Parathyroid Hormone-Related Protein during Pregnancy and the Perinatal Period

Circulating Levels of Biologically Active and Immunoreactive Intact Parathyroid Hormone in Human Newborns

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

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