L. Shandley et al., COLLAGEN IN THE FETAL MEMBRANES OF SHEEP - CHANGES THROUGHOUT GESTATION AND EFFECTS OF DEXAMETHASONE AT 60 DAYS, Reproduction, fertility and development, 9(4), 1997, pp. 455-464
The tensile strength of fetal membranes is largely due to their collag
en content. In this Study we have examined the changes in collagen in
the amniotic and allantoic membranes of the sheep over a wide gestatio
nal range (27-142 days of gestation; term, 145-150 days). The results
have been correlated with volume changes in normal development, and in
particular, the changes in allantois have been studied after a rapid
and extensive increase in allantoic volume, as a result of maternal de
xamethasone treatment (0.76 mg h(-1) for 48 h) from Day 60 of gestatio
n. Electron microscopy and immunohistochemistry were used to delineate
collagen distribution, and gel electrophoresis was used to assess the
relative proportions of each type. In the amnion, collagen content in
creased from 37 +/- 4% to 50 +/- 1% dry weight of the tissue from 41-1
02 days and declined slightly thereafter. In the allantois, collagen c
ontent increased from 20 +/- 1% at Day 27 to 50 +/- 6% at Day 142, sig
nificantly correlated with a volume increase from 25 +/- 3 mt to 813 /- 274 mL. Collagen types I (>85%), III (10%) and small amounts of typ
es IV and V (<5%) were identified in both membranes at all ages. When
allantoic fluid volume was increased rapidly by maternal dexamethasone
infusion, there was a significant decrease in collagen content from 3
8 +/- 6% to 25 +/- 2% (P < 0.05). By immunohistochemistry it was obser
ved that both epithelial cells and fibroblasts were synthesizing colla
gen.