Transplacental 45Ca and 32P flux in the guinea pig: effect of maternal hypercalcaemia and hypocalcaemia

1985 ◽  
Vol 63 (12) ◽  
pp. 1577-1580 ◽  
Author(s):  
L. O. Derewlany ◽  
I. C. Radde
Keyword(s):  
Guinea Pig ◽  
Calcium Gluconate ◽  
Calcium Concentration ◽  
Maternal Plasma ◽  
Ionized Calcium ◽  
Guinea Pig Placenta ◽  
Plasma Calcium Concentration ◽  
P Flux ◽  
Pig Placenta ◽  
Acute Changes

Transplacental 45Ca and 32P flux was measured across the in situ perfused guinea-pig placenta under conditions of acute maternal hypocalcaemia and hypercalcaemia. Maternal hypercalcaemia induced acutely by calcium gluconate infusion caused an increase in maternal-to-fetal 45Ca flux which was proportional to the increase in maternal plasma ionized calcium concentration. Acute maternal hypocalcaemia was induced by EGTA infusion and resulted in a decrease in maternal plasma ionized calcium concentration proportional to a corresponding decrease in transplacental 45Ca transfer. A bolus of calcium gluconate caused a transient decrease in 32P flux, whereas EGTA administration was without significant effect on transplacental 32P transfer. Calcium transport across the placenta is not saturated under conditions of maternal normocalcaemia and may be altered according to acute changes in maternal plasma calcium concentration. Thus, control of maternal-to-fetal calcium transfer does not appear to be at the placental level. This suggests that fetal calcium homeostasis may be regulated by the fetus itself.

The effect of zinc levels in fetal circulation on zinc clearance across the in situ perfused guinea pig placenta

1990 ◽  
Vol 68 (11) ◽  
pp. 1401-1406 ◽  
Author(s):  
P. G. Paterson ◽  
B. Sarkar ◽  
S. H. Zlotkin
Keyword(s):  
Guinea Pig ◽  
Zinc Concentration ◽  
Maternal Plasma ◽  
Fetal Circulation ◽  
Guinea Pig Placenta ◽  
Placental Blood ◽  
Indirect Indicator ◽  
Pig Placenta ◽  
Zinc Levels

Although zinc is essential for normal fetal growth and development, little is known about factors that influence its transfer across the placenta. The in situ perfused guinea pig placenta model was used to study the influence of the zinc concentration of fetal circulation on maternofetal placental zinc transfer. A placenta of the anaesthetized sow was perfused (on the fetal side) with a physiological perfusate via the umbilical vessels, with the fetus excluded. The sow was infused intravenously with 65zinc as a tracer of placental Zn clearance, and with antipyrine as an indirect indicator of maternal placental blood flow. Maternal plasma and placental effluent samples collected at intervals were counted for 65zinc by gamma counter, and the absorbance of nitrosated antipyrine was measured at 350 nm. Varying the mean zinc concentration in the perfusate from 0.176 to 1.87 mg/L had no effect on relative zinc clearance calculated as zinc clearance/antipyrine clearance (mean ± SEM; 0.085 ± 0.010 vs. 0.114 ± 0.018; n = 6; p > 0.05). The results suggest that short-term changes in fetal zinc status do not influence placental zinc transfer.Key words: placenta, zinc, transport, trophoblast.

A mathematical model of parathyroid hormone response to acute changes in plasma ionized calcium concentration in humans

2010 ◽  
Vol 226 (1) ◽  
pp. 46-57 ◽  
Author(s):  
Rajiv P. Shrestha ◽  
Christopher V. Hollot ◽  
Stuart R. Chipkin ◽  
Claus P. Schmitt ◽  
Yossi Chait
Keyword(s):  
Mathematical Model ◽  
Parathyroid Hormone ◽  
Calcium Concentration ◽  
Ionized Calcium ◽  
Hormone Response ◽  
Acute Changes

Transfer of lipids across the guinea pig placenta

1969 ◽  
Vol 104 (4) ◽  
pp. 564-572 ◽  
Author(s):  
Herbert J. Kayden ◽  
Joseph Dancis ◽  
William L. Money
Keyword(s):  
Guinea Pig ◽  
Guinea Pig Placenta ◽  
Pig Placenta

A Mathematical Model of Parathyroid Hormone Response to Acute Changes in Plasma Ionized Calcium Concentration in Humans

2008 ◽  
Author(s):  
Rajiv P. Shrestha ◽  
Yossi Chait ◽  
Christopher V. Hollot ◽  
Stuart Chipkin ◽  
Claus P. Schmitt
Keyword(s):  
Calcium Concentration ◽  
Linear Time ◽  
Ionized Calcium ◽  
Time Varying ◽  
Qualitative Model ◽  
Hormone Response ◽  
Clinical Tests ◽  
Parametrization Scheme ◽  
Normal Humans ◽  
Acute Changes

A complex bio-mechanism, referred to as calcium homeostasis, regulates plasma ionized calcium (Ca++) concentration in the human body to within a narrow physiologic range which is crucial for maintaining normal physiology and metabolism. In this paper we present a qualitative model of the calcium homeostatic system and then focus on a particular sub-system, termed Ca-PTH axis. We consider the dynamics of the axis involving the response of the parathyroid glands to acute changes in plasma Ca++ concentration. We use a two-pool, linear time-varying model to describe the Ca-PTH axis. We show that this model, parameterized using a guided iterative parametrization scheme and induced hypocalcemic clamp test data, successfully predicts dynamics observed in clinical tests of induced hypercalcemia in normal humans.

Molecular charge effects on the protein permeability of the guinea-pig placenta

Placenta ◽  
1987 ◽  
Vol 8 (4) ◽  
pp. 365-380 ◽  
Author(s):  
A. Berhe ◽  
W.G. Bardsley ◽  
A. Harkes ◽  
C.P. Sibley
Keyword(s):  
Guinea Pig ◽  
Charge Effects ◽  
Guinea Pig Placenta ◽  
Molecular Charge ◽  
Pig Placenta ◽  
Protein Permeability
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