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K. BOER
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J. DOGTEROM
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H. F. PRONKER
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The pituitary contents of oxytocin, vasopressin and α-MSH were measured in fetal and newborn rats to assess possible changes in their release during the process of labour. In the 24 h period during which delivery is likely to occur in the Wistar rat, both the oxytocin and vasopressin content of the fetal pituitary gland increased, whereas α-MSH content remained the same. During and/or just before labour, the oxytocin content was found to decrease by 30%, indicating an enhanced fetal release of the hormone at this stage. It was concluded that the expulsion of each fetus did not provide an extra stimulus for release of oxytocin by the fetus.

In addition, if the fetus remained in the uterus after decapitation of the mother, the oxytocin content of the fetal pituitary gland decreased a further 30%. Neither vasopressin nor 30%. content was altered by the process of labour or by the fetus remaining in the uterus after decapitation of the mother. The levels of vasopressin and α-MSH were, however, 20 times higher than the oxytocin content in the fetus and the newborn, which might have obscured the demonstration of a relatively small change in levels of these two hormones.

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J. DOGTEROM
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F. G. M. SNIJDEWINT
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P. PÉVET
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D. F. SWAAB
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The demonstration of vasotocin in the mammalian pineal gland, subcommissural organ and fetal pituitary gland by bioassay has led to hypotheses regarding the function of this hormone in various reproductive processes.

Preliminary examinations of the pineal gland and subcommissural organ with a specific radioimmunoassay failed to show vasotocin immunoreactivity. The presence of vasotocin, vasopressin and oxytocin in the pineal gland, subcommissural organ and fetal neurohypophysis was therefore investigated, using three specific radioimmunoassays. Frog and chicken pituitary glands were used to validate the vasotocin radioimmunoassay.

Direct measurements in diluted homogenates of pituitary glands from frogs, chickens, mid-term fetal sheep and near-term fetal seals revealed the presence of vasotocin only in the frog and chicken pituitary glands, while vasopressin and oxytocin were found in the two fetal pituitary homogenates.

Vasopressin and oxytocin were measured in homogenates of rat and bovine pineal glands and in preparations of the subcommissural organ of rats and rabbits after extraction with Vycor glass powder, but no specific vasotocin immunoreactivity was observed. These results indicate a discrepancy between the reported biological activity of vasotocin in the pineal gland, subcommissural organ and fetal pituitary gland and the immunoreactivity of this material, which can at present only be explained by the presence of a peptide which is structurally closely related to, but not identical with, vasotocin.

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