Effects of insulin-like growth factor I on steroidogenic enzyme expression levels in mouse leydig cells.
The role of IGF-I in Leydig cell maturation was studied by evaluation of: 1) steady state levels for nine mRNA species expressed specifically in Leydig cells of 35- and 50-d-old IGF-I-null mice and wild-type controls; 2) protein levels for 17 alpha-hydroxylase/C17-20 lyase, cholesterol side-chain cleavage, and type I 5 alpha-reductase (5 alpha R-1) in Leydig cells by immunocytochemistry; and 3) serum testosterone (T) and testicular interstitial fluid IGF-I levels. Expression levels of all mRNA species associated with T biosynthesis were lower in the absence of IGF-I stimulation. In contrast, androgen-metabolizing enzyme mRNA species had either normal (3 alpha-hydroxysteroid dehydrogenase) or higher expression (5 alpha R-1) levels in IGF-I-null mice (P < 0.05) relative to wild-type controls. None of the mRNA species studied changed developmentally in the mutant, whereas there were increases or decreases between d 35 and 50 in normal controls. Parallel trends were observed for average Leydig cell 5 alpha R-1 immunostaining intensity. T levels in mutants were initially higher during d 14-21, equivalent to normal on d 28, and then failed to increase pubertally, remaining at 30% of control levels (P < 0.01) in 90-d-old adult animals. In normal wild-type mice, interstitial fluid and plasma IGF-I levels were highest (P < 0.05) on d 24, indicating that the action of this growth factor on the testis peaks during pubertal development. These results show that in the absence of IGF-I, there is a failure of adult Leydig cells to mature, and that the reduced capacity for T production is caused by disproportionate expression of T biosynthetic and metabolizing enzymes.
Wang
Gui-Min
GM
Center for Biomedical Research, The Population Council, and Rockefeller University, New York, New York 10021, USA.
O'Shaughnessy
Peter J
PJ
Chubb
Curtis
C
Robaire
Bernard
B
Hardy
Matthew P
MP
D000375:Aging / Q000097:blood / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000097:blood / Q000254:growth & development / Q000378:metabolism; D042944:Cholestenone 5 alpha-Reductase / Q000378:metabolism*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism*; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis* / Q000097:blood / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D007334:Insulin-Like Growth Factor I; D007985:Leydig Cells / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000378:metabolism; D013194:Staining and Labeling; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism*; D013737:Testis / Q000378:metabolism
D012739:Gonadal Steroid Hormones; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013254:Steroid 17-alpha-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D042944:Cholestenone 5 alpha-Reductase