Lactation And Gestation Controls On Calcium Isotopic Compositions In A Mammalian Model

Lactation and gestation are among the physiological events that trigger the most intense changes in body calcium (Ca) fluxes. Along with the composition of the animal 2021 diet, these events are suspected to impact the Ca isotopic composition of Ca body reservoirs but their dynamics are poorly understood. In this study, we monitored a group of domestic sows across a full reproduction cycle. We collected tissues and fluids (blood, urine, milk, colostrum, umbilical blood, adult and piglet bones) at different steps of gestation and lactation, and analyzed their Ca isotopic compositions (i.e. delta Ca-44/42) by means of multi-collector inductively coupled plasma mass spectrometry. Among other results, we report the first observations of Ca isotopic fractionation between maternal and umbilical blood (Delta Ca-44/42(umbilical blood-sow blood) = -0.18 +/- 0.11 parts per thousand, n = 3). Our data also highlight that gestation and lactation periods are characterized by small diet-bone Ca isotopic offsets (Delta Ca-44/42(bone-diet) = -0.28 +/- 0.11 parts per thousand, n = 3), with Ca-44-enriched blood compositions during nursing (Delta Ca-44/42(nursing blood-gestation blood) = +0.42(-0.12)(+011)parts per thousand, n = 3). Under the light of an up-to-date mammalian box model, we explored different scenarios of gestation and lactation Ca fluxes experienced by a sow-like animal. These simulations suggest that gestation changes on body delta Ca-44/42 values may result from the intensification of Ca absorption by the animal, whereas the production of Ca-44-depleted milk is the main driver for the Ca-44 enrichment in blood during lactation. In addition, our results also support that bone mineralization could be associated with a more restricted Ca isotopic fractionation than previously envisioned. Together, these results refine the framework of Ca isotope applications, notably regarding the monitoring of human bone balance and the study of species and ecosystems from the present and the past.[GRAPHICS].