Calcium Homeostasis in the Foetal Guinea Pig

Graham, R. W.; Scothorne, R. J.

doi:10.1113/expphysiol.1970.sp002049

Cited by 12 publications

(8 citation statements)

References 13 publications

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“…Other possibilities are high calcium binding by fetal proteins or large quantities of citrate. The observed fall in fetal plasma calcium concentration between 16 and 18 days is coincident with the initial phase of skeletal calcification and resembles the findings in the guinea pig [Graham and Scothorne, 1970] [Graham andScothorne, 1970 and1971].…”

Section: Discussionsupporting

confidence: 52%

Fetal‐maternal Plasma Calcium Relationships in the Rabbit

Graham

Porter

1971

Exp Physiol

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Plasma total calcium levels have been studied in pregnant rabbits and their fetuses from 16 days gestation to term. Between 16 and 21 days gestation the observed fetal plasma calcium level falls from the maternal level or above to 1-6 mg/100 ml. below the maternal level. Thereafter, the fetal plasma calcium rises and at 30 days gestation exceeds the maternal level by 1*9 mg/100 ml. There is a high correlation between fetal and maternal levels at 21 days which is lost by 30 days. Fetal skeletal calcification was studied using an alizarin stain technique. The earliest centres of calcification were present in the clavicle and mandible at 16 days. It is concluded that the observed fall in fetal plasma calcium near mid-gestation may be due to the onset of skeletal calcification and the increase after 21 days to one or more of a variety of factors. Five 21 days pregnant animals were infused with 1 per cent calcium chloride solution (1 g anhydrous calcium chloride in 100 g aqueous solution) for up to 2j hr. The maternal plasma calcium concentration was elevated by 7.7 mg/100 ml. during the infusion but the fetal level was only raised by 2-0 mg/100 ml. The correlation between fetal and maternal levels was lost during the infusion. These findings are compatible with either slow calcium transfer across the placenta or fetal calcium homeostasis. It is well established in many mammalian species that during late gestation there is a greater concentration of calcium in fetal than in maternal plasma. In the guinea pig, on the contrary the fetal plasma calcium concentration at mid-gestation falls from about the maternal level (9.6 mg/100 ml.) to 5-5 mg/100 ml. and then slowly rises, reaching the maternal level again only near the end of gestation [Graham and Scothorne, 1970]. This paper presents a study of maternal and fetal levels, from a relatively early stage in gestation, in another species. The rabbit was chosen since there is already some evidence that fetal levels are lower than maternal at 21-23 days of gestation [McIsaac, 1927; Economou-Mavrou and McCance, 1958]. The stage in gestation when the homeostatic mechanism for calcium becomes mature in the fetus has not yet been identified, although there is experimental evidence that the parathyroid can elaborate hormone early in embryonic development [Scothorne, 1964: Graham and Scothorne, 1971]. In late gestation, when fetal calcium levels are higher than maternal, the fetal level remains constant when the level in the mother is elevated by infusion of calcium chloride [Bawden and Wolkoff, 1967: Greeson et al., 1968]. In this work, when low fetal levels earlier in gestation were substantiated, it was decided to study these levels after induction of maternal hypercalcaemia. METHODS The accuracy of the calcium estimation was assessed by preparing nine separate 5 ml. plasma solutions [Fawcett and Wynn, 1961] each containing 0 05 ml. of the same human plasma. The calcium content of each small sample of plasma was determined 160

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Section: Discussionsupporting

confidence: 52%

Fetal‐maternal Plasma Calcium Relationships in the Rabbit

Graham

Porter

1971

Exp Physiol

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“…At term the mammalian fetus has been reported to be hypercalcemic (1-4) and hyperphosphatemic (5-7), conditions which developed over a period of time in the final stages of gestation (10)(11)(12)(13). The present report confirms the gradual buildup of calcium and phosphorus in fetal blood and demonstrates, in addition, that as circulating levels of these elements rise, blood pH falls.…”

Section: Administration Of Ammonium Chloride or Sodium Bicarbonate Tosupporting

confidence: 90%

“…The difference in serum calcium between mother and fetus may, in part, be explained by the observation that the circulating level of this element in the dam falls in the final stages of gestation (5, 8,9). In addition, in the many mammals investigated, the level of calcium in the blood of the fetus has been shown to increase as termination of pregnancy is approached (10)(11)(12). Finally, in the rat, fetal phosphatemia has been shown to parallel the rise in blood calcium in the last days before birth (13).…”

mentioning

confidence: 97%

Acidosis, Hypercalcemia, and Hyperphosphatemia in Rat Fetuses near Term and Effects of Maternal Acid/Base Loading

Krukowski

Smith

1979

Experimental Biology and Medicine

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In most mammalian species examined, the levels of calcium (1-4) and of phosphorus (5-7) in the blood of the fetus at term exceed those of the dam. The difference in serum calcium between mother and fetus may, in part, be explained by the observation that the circulating level of this element in the dam falls in the final stages of gestation (5,8,9). In addition, in the many mammals investigated, the level of calcium in the blood of the fetus has been shown to increase as termination of pregnancy is approached (10-12). Finally, in the rat, fetal phosphatemia has been shown to parallel the rise in blood calcium in the last days before birth (13).We have previously demonstrated that rat fetuses are acidotic near term, and that in utero hypercalcemia and early neonatal hypocalcemia are associated with low blood pH and normalization of blood pH, respectively (14). In view of this apparent association at term and immediately after birth, the present studies were undertaken: (i) to investigate whether in the final stages of gestation fetal blood pH shifts concurrently with reported alterations in the levels of calcium and phosphorus; and (ii) to test the hypothesis that changes in the circulating levels of calcium and phosphorus are causally related to blood pH in the developing mammal in utero, by either aggravating or alleviating the acidotic state of the conceptus by the maternal administration of ammonium chloride or sodium bicarbonate, respectively.Materials and methods. Four-to eightmonth-old pregnant albino rats and their offspring were used. The adult animals were maintained on Purina laboratory chow and tap water ad libitum and housed in a temperature-controlled room illuminated on a 14hr-light/ 10-hr-dark cycle.In order to obtain females at a known time Work supported by National Institutes of Health Grant HD 07419-3.of gestation, the animals were caged with males for a single overnight period. The day of mating was counted as Day 0, and experiments were terminated at preselected times during the last week of pregnancy. Studies on fetuses in the final week of gestation.Beginning on Day 17 and then daily through the 22nd day of pregnancy, groups of animals were handled as follows:The gravid female was lightly anesthetized with ether, a laparotomy was performed, and the pregnant uterus was exposed. Fetuses were sequentially bled and excised until the entire litter was sampled. Fetal blood was taken from the axilla while the placental and umbilical circulations were intact. Tail blood was drawn from the mother at the beginning and end of each experiment.Studies on offspring of pregnant animals receiving either ammoniunt chloride or sodium bicarbonate orally. Pregnant animals were divided into three groups. Beginning on the 17th day of gestation, tap water was removed and the following substitutions were made. One group of animals was given a solution of 1.5% NH4Cl, the second group received a 1.5% solution of NaHC03, and the remaining rats were given distilled water. Animals were allowed to drink freely and fluid...

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“…In human studies it has been demonstrated that plasma Cae' and Ca levels decrease (27) while the serum iPTH increases (28) during the last trimester of pregnancy. In the guinea pig and rabbit the fetal plasma Ca level decreases significantly below the maternal level at approximately mid-gestation, corresponding in the time with the onset of fetal skeletal calcification; subsequently, the fetal plasma Ca concentration increases and exceeds the maternal level at the end of gestation (29,30). In this regard, the findings of Smith et al are important and pertinent to the discussion (26).…”

Section: Discussionmentioning

confidence: 79%

Calcium Metabolism in Newborn Infants THE INTERRELATIONSHIP OF PARATHYROID FUNCTION AND CALCIUM, MAGNESIUM, AND PHOSPHORUS METABOLISM IN NORMAL, “SICK,” AND HYPOCALCEMIC NEWBORNS

David¹,

Anast²

1974

J. Clin. Invest.

189

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A B S T R A C T Serum immunoreactive parathyroid hormone (iPTH) and plasma total calcium, ionized calcium, magnesium, and phosphorus levels were determined during the first 9 days of life in 137 normal term infants, 55 "sick" infants, and 43 hypocalcemic (Ca < 7.5 mg/100 ml; Ca"+ < 4.0 mg/100 ml) infants.In the cord blood, elevated levels of plasma Ca"+ and Ca were observed, while levels of serum iPTH were either undetectable or low. In normal newborns during the first 48 h of life there was a decrease in plasma Ca and Ca", while the serum iPTH level in most samples remained undetectable or low; after 48 h there were parallel increases in plasma Ca and Ca"+ and serum iPTH levels. Plasma Mg and P levels increased progressively after birth in normal infants. In the sick infants, plasma Ca, Ca"+ and P levels were significantly lower than in the normal newborns, while no significant differences were found in the plasma Mg levels. The general pattern of serum iPTH levels in the sick infants was similar to that observed in the normal group, though there was a tendency for the increase in serum iPTH to occur earlier and for the iPTH levels to be higher in the sick infants.In the hypocalcemic infants, plasma Mg levels were consistently lower than in the normal infants after 24 h of age, while no significant differences were found in Dr.

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Calcium Homeostasis in the Foetal Guinea Pig

Cited by 12 publications

References 13 publications

Fetal‐maternal Plasma Calcium Relationships in the Rabbit

Fetal‐maternal Plasma Calcium Relationships in the Rabbit

Acidosis, Hypercalcemia, and Hyperphosphatemia in Rat Fetuses near Term and Effects of Maternal Acid/Base Loading

Calcium Metabolism in Newborn Infants THE INTERRELATIONSHIP OF PARATHYROID FUNCTION AND CALCIUM, MAGNESIUM, AND PHOSPHORUS METABOLISM IN NORMAL, “SICK,” AND HYPOCALCEMIC NEWBORNS

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