INDUCTION OF PREMATURE PARTURITION IN SHEEP: ADRENOCORTICOTROPHIN AND CORTICOSTEROID CHANGES DURING INFUSION OF SYNACTHEN INTO THE FOETUS

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Abstract
Synacthen (10 .mu.g/h) infused into fetal sheep at about day 125 of gestation caused premature delivery within 4 days. During the first 24 h of the infusion the secretion of ACTH was depressed and the assayable hormone concentration was within 500-1000 pg/ml. Subsequently, large fluctuations occurred in the ACTH concentration in the plasma of fetal sheep which were consistent with the stimulation of ACTH secretion. No transfer of Synacthen to non-infused twin fetuses was observed. The plasma corticosteroid concentration in the infused fetus also showed a small rise during the first 24 h of the infusion followed by large fluctuations in concentrations that coincided with the changes in ACTH. No consistent changes in the plasma corticosteroid concentration in the non-infused twin fetus were observed. These results are discussed in relation to the hormone changes occurring during normal delivery.