Ll. Burger et Od. Sherwood, EVIDENCE THAT CELLULAR PROLIFERATION CONTRIBUTES TO RELAXIN-INDUCED GROWTH OF BOTH THE VAGINA AND THE CERVIX IN THE PREGNANT RAT, Endocrinology, 136(11), 1995, pp. 4820-4826
It is well established that cervical growth during rat pregnancy is re
laxin dependent. The first objective of this study was to determine if
relaxin also promotes vaginal growth in the pregnant rat. Finding tha
t this is the case, the second objective of this study was to determin
e if cell proliferation accompanies relaxin-dependent vaginal and cerv
ical growth during rat pregnancy. Primiparous pregnant rats were ovari
ectomized (O) or sham ovariectomized (group C) on day 9 (D9) of pregna
ncy, before relaxin (R) is detectable in the peripheral circulation. A
fter ovariectomy, rats were treated continuously with progesterone (P)
and estrogen (E, group OPE), or P, E, and porcine R (group OPER) in d
oses that restored normal pregnancy and parturition parameters. P and
E were administered via silicon tubing implants. R was administered fr
om miniature osmotic pumps. Vaginas and cervices were collected on D9
and D22 from group C, and on D22 from groups OPE and OPER (n = 6/group
). Vaginas and cervices were weighed, frozen, and lyophilized until dr
y. Dried tissues were weighed, homogenized, and their DNA contents wer
e determined. In sham-operated controls (group C), the wet weight, dry
weight, and DNA contents of both the vagina and cervix increased 50-3
00% from D9-D22. On D22, vaginal and cervical wet and dry weights were
significantly lower than controls in R-deficient group OPE; whereas,
they were greater than controls in group OPER. Similarly, on D22, vagi
nal and cervical DNA content did not differ from D9 controls in group
OPE; whereas they exceeded D22 controls in group OPER. In conclusion,
this study demonstrates that vaginal growth during the second half of
rat pregnancy is R dependent. Additionally, this study provides eviden
ce that R may contribute to both vaginal and cervical growth by promot
ing cellular proliferation.