Croissance osseuse au cours des périodes foetale et néonatale : Rôle du peptide apparenté à l'hormone parathyroïdienne

Parathyroid hormone-related peptide (PTHrP) plays a major role in the regulation of bone growth in the fetus and the neonate. In pregnant and/or lactating ruminant animals, the PTHrP secreted by fetal parathyroid glands and placental membranes stimulates calcium placental transfer from the dam to the fetus. PTHrP also modulates myometrial uterine activity. The expression of the PTHrP gene in pregnant uterus is under the control of mechanical stretch induced by uterine distension following fetal growth. Thus PTHrP controls the rhytmicity and/or force of myometrial contractions during pregnancy Since uterine contractions severely depress blood flow, another possibility is that PTHrP might act to dilate uterine (and placental) blood vessels and assure adequate blood flow to the uterus and feto-placental unit. Conversely, in ewes and goats, the PTHrP released by the lactating mammary gland regulates mammary blood flow and calcium and phosphorus mammary secretion. In neonates, milk PTHrP might control gut motility and calcium and phosphorus intestinal absorption. Thus, by controling calcium placental transfer, myometrial uterine activity, placental and mammary blood flow, milk calcium and phosphorus concentration, and, possibly, calcium and phosphorus intestinal absorption in the newborn, PTHrP regulates skeletal growth during fetal and postnatal periods.

Le peptide apparenté à l’hormone parathyroïdienne (PTHrP) joue un rôle important dans la régulation de la croissance osseuse foetale et néonatale. Chez la femelle gestante et/ou allaitante, l’hormone sécrétée par les parathyroïdes foetales, les membranes placentaires et/ou la glande mammaire en lactation, stimule les transferts calciques placentaires, module la tonicité utérine en fonction de la taille du (ou des) foetus, contrôle le débit artériel mammaire et la teneur du lait en calcium et en phosphore. Chez le nouveau-né, le PTHrP apporté par le lait pourrait intervenir dans la régulation de la motricité intestinale et de l’absorption intestinale du calcium et du phosphore.