Abstract
Summary
After an intra-arterial injection of 10 μg GnRH into four bovine male fetuses, serum LH increased (P < 0.01) 2-fold by 15 min and plateaued at approximately 11 ng/ml from 60 to 180 min. After GnRH in six female fetuses, LH increased (P < 0.01) 7-fold by 15 min and plateaued at approximately 17 ng/ml from 60 to 180 min. Maternal serum LH was not significantly influenced (P > 0.05) by sex of fetus or administration of GnRH to the fetus. After GnRH in male fetuses, serum testosterone increased (P < 0.05) and remained 2-fold greater than basal levels through 180 min. In contrast, serum testosterone from female fetuses averaged 370 ± 60 pg/ml at injection and was unchanged after GnRH.
Androgen synthesis was significantly increased during in vitro incubation of fetal testicular explants by the addition of LH. We conclude that GnRH causes release of LH from the bovine fetal pituitary as early as 120 days of age and that the testes respond with testosterone secretion after LH stimulation.
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