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This Article Full Text Full Text (PDF) All Versions of this Article: 78/4/752    most recent biolreprod.107.065466v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Moore, J. P. Articles by Winters, S. J. PubMed PubMed Citation Articles by Moore, J. P., ,Jr. Articles by Winters, S. J. Agricola Articles by Moore, J. P. Articles by Winters, S. J.

Weaning and the Developmental Changes in Follicle-Stimulating Hormone, Pituitary Adenylate Cyclase-Activating Polypeptide, and Inhibin B in the Male Rat¹

Department of Anatomical Sciences and Neurobiology³ and Division of Endocrinology and Metabolism, Department of Medicine,⁴ University of Louisville School of Medicine, Louisville, Kentucky 40202

ABSTRACT

Pituitary Fshb concentrations increase markedly and selectively beginning on Postnatal Day 20 in the male rat. To evaluate the factors potentially responsible for this rise in FSH, we adjusted the time of weaning, which is generally also on Day 20. Male rat pups were provided nutrients by suckling only and were weaned to laboratory chow earlier (Day 17) or later (Day 23) than normally performed in animal facilities (Day 20). Between ages 17 and 29 days, significant increases were seen in serum LH (1.4-fold) and FSH (2.4-fold) levels; pituitary expression of Lhb (5.4-fold), Fshb (21.3-fold), and inhibin beta B (Inhbb, 2.26-fold) mRNAs; and testicular expression of Inhbb (10-fold) mRNA. Concurrently, significant decreases occurred in serum inhibin B levels (1.8-fold); pituitary adenylate cyclase-activating polypeptide (Adcyap1, 4.2-fold), total follistatin (Fst, 3.5-fold), and Fst isoform 288 (5.6-fold) mRNAs; and testicular expression of inhibin beta A (8.2-fold) mRNA. Early weaning significantly increased serum FSH but not LH and increased pituitary expression of Fshb and GnRH receptor (Gnrhr) mRNAs but not Lhb. Early weaning also significantly decreased serum inhibin B but increased testicular expression of the Inhbb subunit. Early weaning also caused pituitary expression of Fst and Adcyap1 to decline earlier than in the control group. Immediately after weaning, growth accelerated substantially, and the time of weaning produced significant and differential effects on circulating leptin levels that were not related to indices of FSH production. From these observations, we propose the novel hypothesis that the increase in growth rate subsequent to weaning signals circulating inhibin B levels to fall and pituitary Adcyap1 and consequently Fst expression to decrease, and that these events together facilitate the rise in Fshb and Gnrhr expression by increasing pituitary activin signaling.

follicle-stimulating hormone, gonadotropins, inhibin, luteinizing hormone, male reproduction, male sexual function, pituitary

¹Supported in part by NIH grants RR-P20 RR17702-SPID 0005 from the Institutional Development Award (IdeA) Program of the NCRR (J.P.M.) and R01-HD-036034 (S.J.W.), by the Walter F. and Avis Jacobs Foundation, and by the Commonwealth of Kentucky Research Challenge Fund.

Correspondence: ²Joseph P. Moore, Jr., Department of Anatomical Sciences and Neurobiology, School of Medicine, University of Louisville, Louisville, KY 40202. FAX: 502 852 2492; e-mail: jpmoor03{at}louisville.edu