Prolactin in the circulation of chronically catheterised piglet foetuses and pregnant sows, and the effect of thyrotrophin-releasing hormone.
We chronically catheterised 12 piglet foetuses and 11 sows to determine the changes in circulating concentrations of prolactin during the last 2 weeks of gestation. Prolactin levels were measured by homologous radioimmunoassay and were found to average 2.12 +/- 0.23 ng . ml-1 in the foetuses and 4.19 +/- 0.84 ng . ml-1 in the sows. Foetal concentrations of prolactin increased significantly during the time period of the study. There was no change in maternal concentrations over the corresponding time. Injection of 5 micrograms TRH into 7 foetuses increased the plasma concentrations of prolactin in 6 animals, produced no apparent change in the seventh foetus and did not affect maternal concentrations of prolactin. The magnitude of the maximum response of TRH of the younger foetuses (less than 107 days delta = 0.7, 1.3, 4.2 ng . ml-1) was substantially less than that of the foetuses prior to term (greater than 107 days delta = 6.4, 21.7, 27.5 ng . ml-1). Injection of saline and the haemorrhage of blood sampling produced no significant change in the initial concentration of prolactin. We conclude that prolactin is present in the circulation of the pig foetus, that it is produced endogenously in lower concentrations than in the pregnant sow and that the foetal responsiveness to TRH stimulation increases towards the end of gestation.
D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002404:Catheterization; D005260:Female; D005312:Fetal Blood / Q000032:analysis; D005333:Fetus / Q000378:metabolism*; D005865:Gestational Age; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011247:Pregnancy; D011270:Pregnancy, Animal; D011388:Prolactin / Q000097:blood*; D011863:Radioimmunoassay; D013552:Swine / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D002245:Carbon Dioxide; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D010100:Oxygen