Calcitonin effects in primate pregnancy

The acute effects of calcitonin (CT), a hypocalcemic hormone to act by inhibiting bone resorption, were studied in rhesus monkeys in late pregnancy. Salmon CT was injected intravenously into either mother or fetus and the concentration of total calcium and inorganic phosphorus in maternal plasma, fetal plasma, and amniotic fluid measured. Maternal CT administration produced a gradual fall in maternal plasma calcium levels and, to a lesser extent, in maternal plasma phosphorus levels. Both depth and duration of maternal hypocalcemia were related to dose. In addition, the dbree of hypocalcemic response was greater in pregnant than in nonpregnant animals at equivalent dosage levels. Hypocalcemia induced in the mother by CT injection was not reflected in fetal hypocalcemia. Fetal CT administration produced a triphasic response in fetal plasma calcium, consisting of a prompt initial drop followed by a return to or above the baselineand then a more gradual decline. Bth the initial and the secondary hypocalcemic responses in the fetus were dose-related in terms of depth and duration. These observations suggest that CT MAY BE AN IMPORTANT HORMONE IN BOTH MATERNAL AND FETAL PHYSIOLOGY.