Leslie P. Bullock

Part II. Androgen Metabolism and Mechanism of Action in Male Pseudohermaphroditism: A Study of Testicular Feminization

Publisher Summary This chapter discusses androgen metabolism and the mechanism of action in male pseudohermaphroditism. It has been found that testosterone is the major androgen secreted into the blood of most mammals and that this steroid has biological actions on many tissues. As animals with testicular feminization cannot respond to androgens in utero, tissues, such as prostate, Wolffian duct derivatives, and external genitalia, do not differentiate, and the tfm animal develops as a male pseudohermaphrodite. Male pseudohermaphroditism resembling testicular feminization also develops in animals that are deprived of androgens in utero by one of the several mechanisms, including castration, defective testosterone synthesis, and exposure to pharmacologic agents that either block androgen biosynthesis in the testis or androgen action at the end organ. When the gonaducts and external genitalia fail to undergo androgen-dependent differentiation in utero, they do not develop into a normal reproductive tract when subsequently exposed to large doses of androgens. Thus, certain tissues may acquire insensitivity to androgens during differentiation. The chapter also discusses ultrastructural examination of the interstitial area of vet rat testes that demonstrates increased peritubular connective tissue. The interstitial tissue consisted predominantly of fibroblasts and a few peritubular sheath cells.

Early androgen action in kidney of normal and androgen-insensitive (tfm/y) mice. Changes in RNA polymerase and chromatin template activities.

Intranuclear accumulation of testosterone was compared with early changes in transcriptional events in kidneys from normal female and androgen-insensitive (tfm/y) mice. Following a subcutaneous injection of [3H] testosterone, total nuclear uptake of the steroid was maximal at 30 min and declined to about 40% of the peak value by 4 h after hormone administration. After a single subcutaneous dose of testosterone, RNA polymerase activity assayed in intact nuclei in the presence of Mg2+ and alpha-amanitin (nucleolar RNA polymerase I), as well as the enzyme activity sensitive to low concentration of the toxin (nucleoplasmic RNA polymerase II), increased within 15 min and attained peak values at 2 and 1 h, respectively. The activity of both polymerases declined almost to the control level by 4 h and then increased again with a second peak at 20 and 12 h for RNA polymerase I and II, respectively. Similarly, the template capacity of mouse kidney chromatin, as measured with mammalian RNA polymerase II, increased by 15 min, reached a peak at 1 h and returned to control level by 4 h following hormone treatment. A second dose of testosterone given at the nadir (4 h) was not capable of stimulating renal chromatin template activity significantly as compared to the effect observed after the initial hormone treatment. Contrary to the testosterone-stimulated changes in transcriptional events observed in normal female mice, androgens elicited no response in androgen-insensitive tfm/y mice, animals lacking cytosol androgen receptors. These results strongly support the contention that hormone-specific receptors are obligatory to steroid-mediated modifications in gene transcription.

Androgenic, synandrogenic, and antiandrogenic actions of progestins.

In addition to their action on the uterus and vagina, progestins exert diverse metabolic effects on a variety of tissues. These actions include androgenic, synandrogenic, and antiandrogenic effects on androgen-responsive tissues of rats and mice. The androgenic and antiandrogenic effects of progestins have been demonstrated in multiple tissues. These actions appear to be mediated via the androgen receptor. A synandrogenic effect of progestins has also been detected in some tissues. However, there are few data to indicate how this response is mediated. Progestins may also alter androgen action indirectly through changes in steroid synthesis and metabolism. The overall biologic effect of a steroid may thus be determined by the sum of its actions on a variety of tissues.

In vivo androgen retention in mouse kidney

The in vivo retention of 3-H-testosterone, dihydrotestosterone (DHT), 3alpha-androstanediol (3alpha-DIOL), 3beta-DIOL, androstenedione, progesterone and cortisol by renal cytoplasm and nuclei of male and female mice was studied. Testosterone was the major androgen isolated from cytoplasm and nuclei following testosterone or androstenedione administration. By contrast, DHT was the major intracellular androgen after DHT, 3alpha- or 3beta-DIOL injection. The uptake of 3-H-testosterone or 3-H-DHT was abolished by excess unlabeled testosterone, DHT or cyproterone acetate. Androgen concentrations in kidney fractions from female mice were similar to those from males. There was no appreciable concentration of the isolated steroids following 3-H-progesterone administration. 3H-cortisol was concentrated in both cytoplasm and nuclei but was not displaced by non-radioactive androgens. These findings suggest that in contrast to prostate, mouse kidney can concentrate both testosterone and DHT. However, since testosterone is the major androgen in blood and since it is not metabolized in kidney, it is the major effector androgen in this organ. Androstenedione is active via conversion to testosterone while DIOLS are androgenic via metabolism to DHT.

In vivo and in vitro testosterone metabolism by the androgen insensitive rat.

Abstract The androgen insensitive (tfm) rat is a male pseudohermaphrodite with inherited tissue insensitivity to androgens. To understand the nature of this genetic defect better, in vivo and in vitro testosterone metabolism was studied in preputial glands from tfm as well as normal male and female rats. in vivo studies in normal rats indicated that testosterone metabolism in cytoplasm and nuclei of preputial glands was similar to that of normal prostate. In the tfm rat, testosterone uptake by the preputial gland was normal, but dihydrotestosterone (DHT) was not retained in cytoplasm or nuclei. Reduction of testosterone to DHT by 5α-reductase in tissue slices of eight organs as well as preputial gland cytoplasm and nuclei from tfm rats was indistinguishable from that in normal animals. We conclude that the inability of the tfm rat to retain intracellular DHT is due to a defect of a cytoplasmic binding component which normally concentrates DHT in the cell and facilitates its transfer to the nucleus. Since DHT is believed to be one of the intranuclear effectors of testosterone action, the androgen insensitivity of the tfm rat may be explained by the inability to concentrate this steroid at its presumed site of action.

Genetic regulation of the androgen receptor—A study of testicular feminization in the mouse

Abstract Testicular feminization (TFM) is an inherited disorder which is transmitted by females to half their male offspring. Affected individuals are genetic males with end organ insensitivity to androgens. As a consequence, they lack androgen dependent differentiation and present as phenotypic females. Studies on rats and mice indicate that a major tissue abnormality in testicular feminization is decreased cytosol androgen receptor activity. Deficiency of this cytosol binder could account for the lowered nuclear binding of testosterone and dihydrotestosterone in these animals. If androgen uptake and binding in the nucleus is required to initiate RNA and DNA synthesis, then the inability to concentrate androgens at the active site in the nucleus could account for the androgen insensitivity in testicular feminization. The findings in the present study support a direct correlation between the TFM gene, androgen receptor activity and androgen response.

GENETIC REGULATION OF THE ANDROGEN RECEPTOR—A STUDY OF TESTICULAR FEMINIZATION IN THE MOUSE*

Testicular feminization (TFM) is an inherited disorder which is transmitted by females to half their male offspring. Affected individuals are genetic males with end organ insensitivity to androgens. As a consequence, they lack androgen dependent differentiation and present as phenotypic females. Studies on rats and mice indicate that a major tissue abnormality in testicular feminization is decreased cytosol androgen receptor activity. Deficiency of this cytosol binder could account for the lowered nuclear binding of testosterone and dihydrotestosterone in these animals. If androgen uptake and binding in the nucleus is required to initiate RNA and DNA synthesis, then the inability to concentrate androgens at the active site in the nucleus could account for the androgen insensitivity in testicular feminization. The findings in the present study support a direct correlation between the TFM gene, androgen receptor activity and androgen response.