Uterine collagen during pregnancy in cattle.

Uteri were collected at the slaughter of non-pregnant dairy cattle and cattle at various stages of gestation. The weight of the whole uterus increased about 12-fold during the 9 month gestation period. The greatest increase was in the weight of the pregnant horn. The increase in weight of the uterine horns was accompanied by an increase in collagen content. The collagen concentration did not change. The collagen crosslink pyridinoline was identified in pregnant uterine tissues at a level of about 0.13 residues per mole of collagen; this level was the same at the beginning and end of pregnancy.