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Biology of Reproduction, Vol 21, 1051-1056, Copyright © 1979 by Society for the Study of Reproduction

Perinatal Activity of the Hypothalamic-Pituitary-Gonadal Axis in the Lamb. I. Circulating Levels of LH, FSH, Prolactin and Testosterone and in vivo Response to hCG in the First Two Months of Life

S. SAVOIE 1, M. G. FOREST 2, B. BOUREL 1, J. M. SAEZ 3, R. COLLU 1, J. BERTRAND 2, , and J. R. DUCHARME 1

1 Centre de Recherche Pédiatrique, Hôpital Sainte-Justine, Montréal, Québec H3T 1C5
2 INSERM-U. 34, 69332 Lyon, Cedex 1, France
3 U. 162, 69322 Lyon, Cedex 1, France


Episodic fluctuations of FSH, LH, prolactin (PRL) and testosterone (T) were determined in male and female lambs from birth to 2 months of age. Plasma LH and FSH peaks were observed from the first week of life but plasma LH was not consistently followed by an increase in T at 8 weeks. Although plasma FSH and PRL fluctuated with no specific trend observable, plasma FSH was higher in female than in male lambs. During a 6 h observation period, fewer spontaneous peaks of LH or T were observed at 4 weeks than at 2 or 8 weeks of age. A significant in vivo T response to hCG administration at 2, 4 and 8 weeks was observed but the mean T area was greater at 8 weeks. These studies indicate an active hypothalamic-pituitary axis in the newborn lamb of both sexes and early testicular activity. However, the steroidogenic testicular responsiveness to endogenous LH appears to be lower at 8 than at 2 weeks of life. The existence of an early activation of the pituitary gonadal axis in the immature male lamb would suggest its usefulness as an experimental model for the study of early postnatal gonadal activity in man.

Note:
ACKNOWLEDGMENTS This work was carried out within the framework of an INSERM-CRSQ thematic research program and was supported by grants from the Ministère de la Santé et du Bien-Etre, Canada, La Fondation Justine Lacoste-Beaudien, The North Atlantic Treaty Organization (NATO), the Inter-Service Club Foundation (Telethon 78) and l’Institut National de la Sante et de la Recherche Medicale, France (CCP 71-78-103). The authors wish to thank Drs. C. Faiman, G. D. Niswender and H. Guyda who have kindly provided some of the antisera used in this study and Mr. G. Ducharme who has provided the statistical analysis. The expert technical assistance of Ms. G. Alberti, A. Lecoq and D. Ivelja and the secretarial help of Ms. Gisèle Jacob are gratefully acknowledged.

Submitted on April 10, 1979
Accepted on August 10, 1979






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Copyright © 1979 by the Society for the Study of Reproduction.