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- Author: R. M. BUCKLE x
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SUMMARY
The quantity of free fatty acids (FFA) released from rat epididymal fat pads in vitro and their concentration within the tissue were determined. The addition of adrenaline, adrenocorticotrophic hormone (ACTH), thyroid stimulating hormone (TSH) and growth hormone (GH) each increased the release of FFA, and their respective minimum effective concentrations were 0·125, 0·004, 0·5 and 1·25 μg./ml. of medium. In every case, the increased release of FFA was associated with a rise in the quantity present within the pads, and the amount released closely paralleled their concentration within the tissue.
It is suggested that the stimulatory effect of all four hormones on the release of FFA from adipose tissue is largely a manifestation of their activity of increasing the concentration of FFA within the cells, and this they do by facilitating the net conversion of storage triglyceride to fatty acid. The significance of the relative activities of the hormones in vitro is discussed and compared with their fatty acid mobilizing effects in vivo.
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SUMMARY
The influence of plasma magnesium concentration on parathyroid gland function has been evaluated by perfusion at a constant rate of an isolated parathyroid gland in five goats and one sheep with whole blood of varying magnesium content. The concentration of magnesium in fresh whole blood was adjusted either by dialysis or by the addition of magnesium chloride before the perfusion. In each experiment, the concentration of calcium was maintained constant or was slightly altered to oppose the possible influence of magnesium on the rate of release of parathyroid hormone. Parathyroid hormone concentration in parathyroid venous plasma was estimated by a specific radioimmunoassay.
In each experimental animal we observed that the concentration of parathyroid hormone in the effluent plasma diminished when the concentration of magnesium was raised or increased when the concentration of magnesium was lowered. These observations demonstrate a specific influence of magnesium on the rate of release of parathyroid hormone.
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SUMMARY
Measurable levels of immunoassayable parathyroid hormone (PTH) were present in the plasma of two out of five sheep foetuses of 80–142 days gestational age, and in three of the mothers at Caesarian section. There was no correlation between foetal and maternal concentrations although the range of values was similar.
In response to foetal hypocalcaemia induced by EDTA infusion the plasma PTH concentration rose in all of the foetuses and there was a highly significant inverse correlation between the foetal plasma calcium and PTH levels. During the period of foetal hypocalcaemia the maternal plasma PTH levels did not change significantly. EDTA was also infused into three adult ewes. There was a similar rise in the concentration of PTH in the plasma of these ewes and it was concluded that the level of responsiveness of the foetal parathyroid gland to plasma calcium concentration was similar to that of the adult.
The parathyroid glands would appear to be active from an early stage in foetal life and responsive to changes in serum calcium level.
