Theca interna

Ovarian follicles, the basic unit of the ovary, consist of an outer layer of theca interna cells which encircle inner layers of granulosa cells. Granulosa cells, in turn, surround the innermost oocyte-cumulus complex. This complex array of cell layers is essential for the maturation and ovulation of the ovum. Significantly, the granulosa cell, by virtue of its close interaction with the outer theca and inner oocyte-cumulus compartment, serves to integrate information necessary for the achievement of successful follicular development. 

Mainly based on rat studies, a two-cell, two-gonadotropin hypothesis for ovarian estrogen biosynthesis has been proposed [63]. According to this model, LH stimulates the biosynthesis of androgens from cholesterol in the theca interna com-... 

Careful analysis of the biosynthetic properties of the membrana granulosa, the theca interna, and luteinized cells of the Graafian follicle and corpus luteum have revealed some of the factors determining the secretory products of these structures, but the role of the ovarian interstitial tissue is not completely established. There is much evidence suggesting that the latter tissue may secrete the major portion of ovarian androgens in women and in virilizing syndromes accompanying ovarian disease (Gil, L4, Mia, M5). 

P450 11A1 is found primarily in steroidogenic tissues, that is, adrenal cortex and gonads, including ovary (corpus luteum " - " and theca interna cells and others ). Of interest are recent reports of P450 llAl in brain" "" and pancreas" . 

Lipid droplets in the cells of the theca interna resembling those in the interstitial cells and luteum cells were pictured by Mulon (1912), Long and Evans (1922), Yamauchi (1926), and others. In 1922 Mulon maintained that secretions of the follicle were responsible for the phenomena of estrus in lower mammals, and Bouin, in commenting on this paper, made the suggestion that the theca interna might secrete the follicular hormone. Subsequent studies supporting this hypothesis are to be found in the review by Corner (1938). 

Dempsey and Bassett (1943) examined the rat s ovary and contributed several additions and modifications to the methods introduced by Bennett. Phenylhydrazones and birefringent crystals were found in the thecae internae of follicles, in the lutein cells, and in the epithelioid interstitial cells. Moreover, it was shown that ultraviolet light produced such intense fluorescence of the phenylhydrazones that 20-micron sections could be employed instead of the thicker ones used previously. Thus it was demonstrated conclusively that the phenylhydrazones occurred within the lipid droplets. 

Histochemical study has shown that lipid droplets reacting by the various tests so far developed for steroids and carbonyl groups are normally present in the cells of the theca interna of the follicle, in the... 

---