Abstract
ABSTRACT: To investigate further the role of the hypothalamic luteinizing hormone releasing factor (LRF) pulse generator and the pituitary LRF receptor in the regulation of gonadotropin secretion and gonadal steroidogenesis in the ovine (O) fetus and neonatal lamb, we measured the increment (the difference between the concentration of plasma LH at time 0 and peak LH) in oLH (AoLH) and oFSH (AoFSH) responses to a potent LRF agonist, D-Trp6Pro9NEt-LRF (LRF-A), after consecutive daily doses in 17 ovine fetuses (six females, 11 males) and in 15 neonatal lambs (six females, nine males). Seven of the lambs had been studied as fetuses. In addition, plasma concentrations of testosterone (T) and androstenedione (A4A) were measured in nine male fetuses. After a stimulatory response to the first dose of LRF-A, the mean AoLH and AoFSH responses in the 106- to 118-d gestation fetuses of both sexes were significantly suppressed by the fourth dose and in the neonatal lamb by the second dose. Suppression was sustained throughout the duration of LRF-A therapy which included the gestational interval when the fetal pituitary exhibits its greatest responsiveness to an acute dose of synthetic LRF. The duration of oLH and oFSH suppression after cessation of LRF-A therapy was studied by measuring the AoLH and AoFSH responses to LRF before and at intervals after LRF-A therapy. In the fetus, the AoLH and AoFSH responses remained significantly decreased 7-8 d after the agonist was discontinued. No statistical differences were detected in the AoLH and AoFSH responses to LRF in the neonatal lamb at least by the 4th d after discontinuation of LRF-A. Increasing the duration of LRF-A therapy did not prolong the length of recovery of LH and FSH responsiveness to LRF in either fetus or neonate. Mean fetal plasma T levels rose significantly in response to a single dose of LRF or LRFA. Peak T responses to single dose LRF or LRF-A were lower on d 2-4 and d 7 than on the 1st d of LRF-A
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Clark, S., Hauffa, B., Rodens, K. et al. Hormone Ontogeny in the Ovine Fetus: XIX: The Effect of a Potent Luteinizing Hormone-Releasing Factor Agonist on Gonadotropin and Testosterone Release in the Fetus and Neonate'. Pediatr Res 25, 347–352 (1989). https://doi.org/10.1203/00006450-198904000-00007
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DOI: https://doi.org/10.1203/00006450-198904000-00007
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