Dynamics of insulin-like factor 3 and its receptor expression in boar testes.
Relaxin-like factor (RLF), now mainly known as insulin-like factor 3 (INSL3), is essential for testis descent during fetal development; however, its function in the adult testis is still being elucidated. As a major step toward understanding the as-yet-unknown function of INSL3 in boars, this study aimed to develop a time-resolved fluoroimmunoassay for boar INSL3, characterize the dynamics of INSL3 expression during development, and demonstrate the expression of the INSL3 hormone-receptor system in the testis. All samples were collected from Duroc boars. The sensitivity of the assay system established was 8.2 pg/well (164 pg/ml), and no cross-reactivity with other hormones, such as porcine relaxin, was observed. Circulating INSL3 was shown to increase progressively during development. INSL3 secreted from the Leydig cells was released not only into the blood circulation but also into the interstitial and seminiferous compartments in sufficient concentrations. A testicular fractionation study revealed that its receptor RXFP2 transcripts were expressed mainly in testicular germ cells. In addition, INSL3 bound to the germ cell membranes in a hormone-specific and saturable manner. These results reveal that INSL3 secreted into the interstitial compartment from the Leydig cells is transported into the seminiferous compartments, where its receptor RXFP2 is expressed mainly in the germ cells to which INSL3 binds, suggesting that INSL3 functions as a paracrine factor on seminiferous germ cells.
Laboratory of Animal Reproduction and Physiology, Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan Division of Animal Resource Production, The United Graduate School of Agricultural Science, Gifu University, Gifu, Japan Shizuoka Swine and Poultry Experimental Station, Kikugawa, Shizuoka, Japan Laboratory of Animal Reproduction, School of Veterinary Medicine, Kitasato University, Towada, Japan School of Veterinary Medicine, Animal Sciences High-Tech Research Center, Kitasato University, Towada, Japan.
Itaru
I
Minagawa
Dai
D
Sagata
Ali Mohammed
AM
Pitia
Hiroshi
H
Kohriki
Masatoshi
M
Shibata
Hiroshi
H
Sasada
Yoshihisa
Y
Hasegawa
Tetsuya
T
Kohsaka
D000818:Animals; D005854:Germ Cells / Q000378:metabolism; D007328:Insulin / Q000235:genetics* / Q000378:metabolism; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D011972:Receptor, Insulin / Q000235:genetics* / Q000378:metabolism; D034421:Sus scrofa / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D013737:Testis / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*
D007328:Insulin; C084797:Leydig insulin-like protein; D011506:Proteins; D011972:Receptor, Insulin
RLF/INSL3; RXFP2; boar; testis