pH and the Level of Calcium in the Blood of Fetal and Neonatal Albino Rats

Abstract

Near-term rat fetuses in utero are acidotic and hypoxic, and have high levels of total serum calcium. In the first hour of postnatal life, pO₂ and pH increase and pCO₂ and calcium fall. Between 1 and 4 h following birth, respiratory gases vary little, whereas pH continues to rise and calcium further declines. By 4 h, newborns reach normal pH levels but are markedly hypocalcemic. It is suggested that the Ê»hypercalcemia’ of intrauterine life is related to acidosis in utero, and that following birth, the initial fall in serum calcium is associated with the blowing off of CO₂ and a concomitant rise in pH. The later decline in circulating calcium is independent of alterations in respiratory gases and relates directly to the final correction of neonatal acidosis.

Age and Organ Dependent Spontaneous Generation of Nuclear 8-Hydroxydeoxyguanosine in Male Fischer 344 Rats

“…However, we could immunohistochemically detect 8-OHdG in the brain stem and kidney, but not in the liver, immediately after birth. The data thus indicate that rats are indeed confronted with early-postnatal oxidative stress (Gunther et al, 1993;Krukowski and Smith, 1976;Yoshimura et al, 1988). The discrepancy between our findings and those of Randerath et al (1997) may be, at least partly, due to the differences in detection methods (they apply 32 P-postlabeling) and the possible presence of mitochondrial DNA contamination.…”

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

“…Typically the fetal serum calcium is 0.30 -0.50 mM or higher than the maternal level in rhesus monkeys (189,524), lambs (148,201,435,505), calves (201,715), rodents (201,338,340,342,346,347,623), pigs (98,101,353), and foals (201). The ionized calcium is also increased 0.25-0.50 mM above the maternal value in fetal rodents (148,340,422), confirming that true hypercalcemia is present relative to maternal and normal adult values.…”

“…It is unknown how early in gestation the serum calcium becomes increased compared with the maternal value, but it has been demonstrated at all time points for which it has been technically possible to measure it. This includes the 35th day of gestation in lambs (93,397), day 14 in rats (346,347,675), and day 15 in mice (330). Within rat fetuses, a small but progressive increase in total and ionized calcium occurs over the final 7 days, which may indicate that at an earlier time point there is no difference between embryonic/fetal and maternal calcium concentrations (346,675).…”

“…During the next 24 h, the serum calcium increases to the adult value. In rodents, the serum calcium drops more markedly by 40% after birth (201,347). If the fetal blood calcium is lower than normal, conceivably the neonatal blood calcium will fall to an even lower value, thereby conferring an increased risk of hypocalcemic tetany and death.…”

“…The serum calcium and ionized calcium fall 40% during the first 6 -12 h after birth in rodents (201,347). Total calcium then rises steadily to reach adult levels by 7-14 days after birth (201,422).…”