Testosterone levels in plasma and testes of neonatal mice.
Newborn female and male C57BL6 mice were decapitated at birth or at different times during the first 24 h after birth and testosterone was determined by radioimmunoassay in plasma and testes. In newborn females, plasma testosterone is low and does not significantly change over the first 24 h after birth. In contrast, in newborn males, plasma testosterone more than doubles during the first 2 h after birth and then falls rapidly to remain relatively low for the remainder of the 24 h period after birth. The increase in plasma testosterone is of almost certain testicular origin since it follows a decrease in testicular testosterone content. It seems likely that the increase in plasma testosterone in male mice which reaches its peak at 2 h after birth is involved in an essential way in the development of well-documented sex differences in gonadotropin secretion and behavior.
Motelica-Heino
I
I
Laboratoire d'Endocrinologie, Université Paris XI, Orsay, France.
Castanier
M
M
Corbier
P
P
Edwards
D A
DA
Roffi
J
J
D000375:Aging; D000735:Androstenedione / Q000032:analysis; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011863:Radioimmunoassay; D012016:Reference Values; D012737:Sex Factors; D013737:Testis / Q000032:analysis / Q000254:growth & development*; D013739:Testosterone / Q000032:analysis* / Q000097:blood
D013739:Testosterone; D000735:Androstenedione