Plasma calcium homeostasis in the guinea pig during the perinatal period.

In pregnant guinea pigs on day 60 of gestation, maternal hypercalcemia induced by calcium infusion (10 mg Ca/kg body weight/h, during 2 h) had no significant effect on the fetal plasma calcium level. By contrast, on day 66 of gestation the same infusion of calcium into the pregnant female induced a significant rise both in maternal and fetal plasma calcium levels. This difference might be related to the variations in the efficiency of placental calcium transfer occurring during the last days of gestation in the guinea pig. Plasma calcium, phosphate and magnesium levels decrease during the 12 h following birth in suckling guinea pigs. Plasma calcium and magnesium concentrations returned to normal values at 24 h while plasma phosphate levels increased during the first week of postnatal life.