G. Min et Od. Sherwood, LOCALIZATION OF SPECIFIC RELAXIN-BINDING CELLS IN THE OVARY AND TESTIS OF PIGS, Biology of reproduction, 59(2), 1998, pp. 401-408
It is not known whether relaxin has physiological roles in the gonads
in mammalian species. Limited evidence indicates that relaxin may act
locally to regulate ovarian function in pigs. The possibility of a rol
e for relaxin in testicular function in pigs has not been investigated
. A major initial step toward the establishment of direct effects of r
elaxin on the ovary and/or testis is to demonstrate that relaxin binds
with specificity to the gonads. Accordingly, the first objective of t
his study was to employ an immunohistochemical localization technique
to determine whether relaxin-binding cells are present in the ovaries
and/or testis of pigs. Once they were found to be present, the second
objective was to determine whether relaxin-binding sites noticeably ch
ange either within the ovary at different stages of the estrous cycle
and pregnancy, or within the testis at sexual maturity. Ovaries were c
ollected from four stages of the estrous cycle (midfollicular, late fo
llicular, early luteal, and midluteal) and three stages of the pregnan
cy (Day 40, Day 80, and Day 110). Two gilts were used for each of the
stages of the estrous cycle and pregnancy. Testes were collected from
a 5-mo-old immature boar and a 36-mo-old mature boar. Tissues were cut
into cubes (3-4 cm(3)), frozen in liquid nitrogen, and cryosectioned
(8 mu m). Specific cell types that bind relaxin were identified by seq
uential application of a biotinylated relaxin probe, antibiotin immuno
globulin G conjugated to 1 nm colloidal gold, and silver for signal am
plification. In the ovary, specific relaxin-binding sites were localiz
ed in both the theca and granulosa cells of developing follicles, lute
al cells, and blood vessels. In the testis, specific relaxin-binding s
ites were localized in the Leydig cells. There were no apparent differ
ences in relaxin-binding distribution within the ovary at different st
ages of the estrous cycle and pregnancy in gilts, or within the testis
at sexual maturity in boars. We conclude that the specific relaxin-bi
nding cells within the ovary and testis of the pig may contain relaxin
receptors. Therefore, relaxin may have effects in the ovary and testi
s of pigs.