The distribution of the growth of collagen in the uterus of the pregnant rat

Abstract

In a previous paper it was reported that rapid formation of collagen took place in the rat's uterus during pregnancy, and that the quantity formed depended upon the number of foetuses present. It was thought probable that mechanical distension by the growing contents played an important part in determining this relationship. No direct evidence was, however, obtained to support this view and it was possible, though perhaps unlikely, that the relation could be entirely explained by local growth of collagen at the placental sites, rather than in the remainder of the uterus which is stretched by the growth of the contents. We have now investigated these two parts separately, and found that the growth of collagen is mainly in the distended part. We have also investigated the change in area of the expanding uterine wall in order to define more exactly the quantitative relation between mechanical stretching and collagen formation. METHODSThe rats used were albinos from the local stock. They weighed approximately 180-200 g at the start of pregnancy, which was timed by the same method as we have used before (Harkness & Harkness, 1954). They were killed by a blow on the head and breaking the neck. The placental sites were removed by cutting round the edge of the placenta, seen through the wall of the uterus before it was opened. The foetuses and associated structures were removed. The placental sites and rest of the wall of the uterine horn were analysed separately, each horn being cut off at the cervical end from the cervix. Collagen was extracted with hot trichloroacetic acid (Fitch, Harkness & Harkness, 1955). The specimens were placed in centrifuge tubes in about ten times their weight of 5% (w/v) trichloroacetic acid and heated for I hr at about 900 C. (temperature of gentle decomposition of the acid). They were then centrifuged and the supernatant removed. The solid was homogenized in 5% trichloroacetic acid in a Potter-Elvehjem homogenizer and heated for a further i hr as before. After centrifuging the supernatant was removed and the solid extracted three times with cold trichloroacetic acid. The bulked trichloroacetic acid extracts were made up to a suitable volume with distilled water and an aliquot, usually one-tenth, taken to dryness in a small beaker on a boiling water-bath, washed with 6N-HCI into a test-tube, sealed and hydrolysed in an autoclave at 40 Lb./sq.in. (2-8 kg/cm2) for 4 hr. Hydroxyproline in the hydrolysate was estimated by the method of Neuman & Logan (1950), and the resultant figure converted to weight

Proceedings of the Physiological Society

“…These results show that: (1) an acute preparation may be satisfactorily used for investigation of factors influencing thyroid function, thus confirming Soderberg (1958); (2) the thyroid responds rapidly to an increased concentration of TSH in the blood; and (3) electrical stimulation of the region of the supraoptico-hypophysial tract in the hypothalamus causes an increase in thyroid activity, as observed by Harris & Woods (1958) (Harkness & Harkness, 1956) suggested that distension is a major factor in stimulating growth of the collagen in the uterus during pregnancy. It is impossible, however, to exclude other local influences, and the present work was designed to test directly the effect of distension.…”

The time‐course and route of loss of collagen from the rat's uterus during post‐partum involution

“…It is known that this factor plays an important part in determining the growth of collagen in the uterus in pregnancy , 1956 R. D. HARKNESS AND BRENDA E. MORALEE in the group, the sole criterion for exclusion being the number of foetuses. This procedure is defective in the early stages after parturition as it only gives useful information about the mean values and none about the variability which is largely due to variation in the number of foetal sites.…”

The effect of the oestrous cycle and of hormones on the collagen content of the uterus of the rat

“…Thus it appears that under hormonal treatment the uterus behaves like other organs subjected to a stimulus to growth, in showing collagen formation 18-2 277 278 Harkness, 1956b). The relatively small amount of collagen formation which takes place in pregnancy in an empty horn could be produced by progesterone, which is presumably circulating in large amounts, since large amounts are required to maintain pregnancy in spayed animals (Alexander & Frazer, 1954).…”