Weaning and the developmental changes in follicle-stimulating hormone, pituitary adenylate cyclase-activating polypeptide, and inhibin B in the male rat.
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.
Moore
Joseph P
JP
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA. jpmoor03@louisville.edu
Winters
Stephen J
SJ
D000375:Aging; D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood* / Q000235:genetics; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics; D038681:Follistatin / Q000235:genetics; D007265:Inhibins / Q000097:blood* / Q000235:genetics; D020738:Leptin / Q000097:blood; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics; D008297:Male; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000097:blood* / Q000235:genetics; D010902:Pituitary Gland / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011966:Receptors, LHRH / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012727:Sex Characteristics; D013737:Testis / Q000737:chemistry; D014886:Weaning; D015430:Weight Gain
D037201:Follicle Stimulating Hormone, beta Subunit; D038681:Follistatin; D020738:Leptin; D037101:Luteinizing Hormone, beta Subunit; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D011966:Receptors, LHRH; C422364:inhibin B; D007265:Inhibins; D005640:Follicle Stimulating Hormone