Differential distribution of type IV collagen chains in the developing rat testis and ovary

Abstract

The localization of type IV collagen α1- α5 chains in the differentiating rat testis and ovary was studied by immunocytochemistry. The initial formation of the testis and ovary included the appearance of collagen α1/ α2(IV) chains in the gonadal blastemas. Upon further differentiation of the epithelia of the gonads α1/ α2(IV) chains became localized in all of the respective basement membranes (BMs). The α3, α4 and α5 chains of type IV collagen were not detectable in the prenatal rat testis and ovary. With the postnatal differentiation of the rat testis the α3- α5(IV) chains gradually appeared, and were localized in BMs of the testicular cords and seminiferous tubules, rete cords, myoid cells, surface epithelium, Leydig cells, and in some blood vessels. In the postnatal rat ovary, the α3(IV) chain appeared in the BMs of small cortical follicles whereas the BMs of secondary and more deeply localized follicles were devoid of this chain. The α1/ α2(IV) chains were abundant in the theca. A reaction for α3- α5(IV) chains also appeared in the BM of the ovarian surface epithelium and of some blood vessels after birth. The present results show that the α3- α5(IV) chains are not only less widely distributed than the α1/ α2(IV) chains but are also synthesized much later in development. The late appearance of the α3- α5(IV) chains shows that the development of the mature testicular and ovarian BMs is a long process and that the time schedule for the synthesis of these chains is different from that of many other extracellular matrix proteins. A careful analysis of the expression of α3(IV) chain may be useful in the further study of the kinetics and regulation of ovarian follicular growth.