Leydig Cells: Steroid-producing cells in the interstitial tissue of the TESTIS. They are under the regulation of PITUITARY HORMONES; LUTEINIZING HORMONE; or interstitial cell-stimulating hormone. TESTOSTERONE is the major androgen (ANDROGENS) produced.Leydig Cell Tumor: Gonadal interstitial or stromal cell neoplasm composed of only LEYDIG CELLS. These tumors may produce one or more of the steroid hormones such as ANDROGENS; ESTROGENS; and CORTICOSTEROIDS. Clinical symptoms include testicular swelling, GYNECOMASTIA, sexual precocity in children, or virilization (VIRILISM) in females.Testis: The male gonad containing two functional parts: the SEMINIFEROUS TUBULES for the production and transport of male germ cells (SPERMATOGENESIS) and the interstitial compartment containing LEYDIG CELLS that produce ANDROGENS.Testosterone: A potent androgenic steroid and major product secreted by the LEYDIG CELLS of the TESTIS. Its production is stimulated by LUTEINIZING HORMONE from the PITUITARY GLAND. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to DIHYDROTESTOSTERONE or ESTRADIOL.Chorionic Gonadotropin: A gonadotropic glycoprotein hormone produced primarily by the PLACENTA. Similar to the pituitary LUTEINIZING HORMONE in structure and function, chorionic gonadotropin is involved in maintaining the CORPUS LUTEUM during pregnancy. CG consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is virtually identical to the alpha subunits of the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity (CHORIONIC GONADOTROPIN, BETA SUBUNIT, HUMAN).3-Hydroxysteroid Dehydrogenases: Catalyze the oxidation of 3-hydroxysteroids to 3-ketosteroids.Receptors, LH: Those protein complexes or molecular sites on the surfaces and cytoplasm of gonadal cells that bind luteinizing or chorionic gonadotropic hormones and thereby cause the gonadal cells to synthesize and secrete sex steroids. The hormone-receptor complex is internalized from the plasma membrane and initiates steroid synthesis.Luteinizing Hormone: A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Luteinizing hormone regulates steroid production by the interstitial cells of the TESTIS and the OVARY. The preovulatory LUTEINIZING HORMONE surge in females induces OVULATION, and subsequent LUTEINIZATION of the follicle. LUTEINIZING HORMONE consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH and FSH), but the beta subunit is unique and confers its biological specificity.Mesylates: Organic salts or esters of methanesulfonic acid.Sertoli Cells: Supporting cells projecting inward from the basement membrane of SEMINIFEROUS TUBULES. They surround and nourish the developing male germ cells and secrete ANDROGEN-BINDING PROTEIN and hormones such as ANTI-MULLERIAN HORMONE. The tight junctions of Sertoli cells with the SPERMATOGONIA and SPERMATOCYTES provide a BLOOD-TESTIS BARRIER.Cholesterol Side-Chain Cleavage Enzyme: A mitochondrial cytochrome P450 enzyme that catalyzes the side-chain cleavage of C27 cholesterol to C21 pregnenolone in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP11A1 gene, catalyzes the breakage between C20 and C22 which is the initial and rate-limiting step in the biosynthesis of various gonadal and adrenal steroid hormones.Seminiferous Tubules: The convoluted tubules in the TESTIS where sperm are produced (SPERMATOGENESIS) and conveyed to the RETE TESTIS. Spermatogenic tubules are composed of developing germ cells and the supporting SERTOLI CELLS.Steroids: A group of polycyclic compounds closely related biochemically to TERPENES. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (STEROLS), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. (From Hawley's Condensed Chemical Dictionary, 11th ed)Steroid 17-alpha-Hydroxylase: A microsomal cytochrome P450 enzyme that catalyzes the 17-alpha-hydroxylation of progesterone or pregnenolone and subsequent cleavage of the residual two carbons at C17 in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP17 gene, generates precursors for glucocorticoid, androgen, and estrogen synthesis. Defects in CYP17 gene cause congenital adrenal hyperplasia (ADRENAL HYPERPLASIA, CONGENITAL) and abnormal sexual differentiation.Spermatogenesis: The process of germ cell development in the male from the primordial germ cells, through SPERMATOGONIA; SPERMATOCYTES; SPERMATIDS; to the mature haploid SPERMATOZOA.Cryptorchidism: A developmental defect in which a TESTIS or both TESTES failed to descend from high in the ABDOMEN to the bottom of the SCROTUM. Testicular descent is essential to normal SPERMATOGENESIS which requires temperature lower than the BODY TEMPERATURE. Cryptorchidism can be subclassified by the location of the maldescended testis.Testicular Neoplasms: Tumors or cancer of the TESTIS. Germ cell tumors (GERMINOMA) of the testis constitute 95% of all testicular neoplasms.Sexual Maturation: Achievement of full sexual capacity in animals and in humans.Pregnenolone: A 21-carbon steroid, derived from CHOLESTEROL and found in steroid hormone-producing tissues. Pregnenolone is the precursor to GONADAL STEROID HORMONES and the adrenal CORTICOSTEROIDS.Dibutyl Phthalate: A plasticizer used in most plastics and found in water, air, soil, plants and animals. It may have some adverse effects with long-term exposure.Antispermatogenic Agents: Agents, either mechanical or chemical, which destroy spermatozoa in the male genitalia and block spermatogenesis.17-Hydroxysteroid Dehydrogenases: A class of enzymes that catalyzes the oxidation of 17-hydroxysteroids to 17-ketosteroids. EC 1.1.-.Androgens: Compounds that interact with ANDROGEN RECEPTORS in target tissues to bring about the effects similar to those of TESTOSTERONE. Depending on the target tissues, androgenic effects can be on SEX DIFFERENTIATION; male reproductive organs, SPERMATOGENESIS; secondary male SEX CHARACTERISTICS; LIBIDO; development of muscle mass, strength, and power.DAX-1 Orphan Nuclear Receptor: An orphan nuclear receptor that is implicated in regulation of steroidogenic pathways. It is unlike most orphan nuclear receptors in that it appears to lack an essential DNA-binding domain and instead acts as a transcriptional co-repressor. Mutations in the gene Dax-1 cause congenital adrenal hypoplasia.Follicle Stimulating Hormone: A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Follicle-stimulating hormone stimulates GAMETOGENESIS and the supporting cells such as the ovarian GRANULOSA CELLS, the testicular SERTOLI CELLS, and LEYDIG CELLS. FSH consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity.Cell Count: The number of CELLS of a specific kind, usually measured per unit volume or area of sample.Organ Size: The measurement of an organ in volume, mass, or heaviness.Seminiferous Epithelium: The epithelium lining the seminiferous tubules composed of primary male germ cells (SPERMATOGONIA) and supporting SERTOLI CELLS. As SPERMATOGENESIS proceeds, the developing germ cells migrate toward the lumen. The adluminal compartment, the inner two thirds of the tubules, contains SPERMATOCYTES and the more advanced germ cells.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Gonadotropins: Hormones that stimulate gonadal functions such as GAMETOGENESIS and sex steroid hormone production in the OVARY and the TESTIS. Major gonadotropins are glycoproteins produced primarily by the adenohypophysis (GONADOTROPINS, PITUITARY) and the placenta (CHORIONIC GONADOTROPIN). In some species, pituitary PROLACTIN and PLACENTAL LACTOGEN exert some luteotropic activities.Sertoli-Leydig Cell Tumor: A sex cord-gonadal stromal tumor consists of LEYDIG CELLS; SERTOLI CELLS; and FIBROBLASTS in varying proportions and degree of differentiation. Most such tumors produce ANDROGENS in the Leydig cells, formerly known as androblastoma or arrhenoblastoma. Androblastomas occur in the TESTIS or the OVARY causing precocious masculinization in the males, and defeminization, or virilization (VIRILISM) in the females. In some cases, the Sertoli cells produce ESTROGENS.Aromatase: An enzyme that catalyzes the desaturation (aromatization) of the ring A of C19 androgens and converts them to C18 estrogens. In this process, the 19-methyl is removed. This enzyme is membrane-bound, located in the endoplasmic reticulum of estrogen-producing cells of ovaries, placenta, testes, adipose, and brain tissues. Aromatase is encoded by the CYP19 gene, and functions in complex with NADPH-FERRIHEMOPROTEIN REDUCTASE in the cytochrome P-450 system.Testicular Hormones: Hormones produced in the testis.Cyclic AMP: An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.Androstane-3,17-diol: The unspecified form of the steroid, normally a major metabolite of TESTOSTERONE with androgenic activity. It has been implicated as a regulator of gonadotropin secretion.Sertoli Cell Tumor: Gonadal neoplasm composed entirely of SERTOLI CELLS or may have a component of GRANULOSA CELLS. Some of the Sertoli cell tumors produce ESTROGEN or ANDROGENS, but seldom in sufficient quantity to cause clinical symptoms such as FEMINIZATION or masculinization (VIRILISM).Testicular Diseases: Pathological processes of the TESTIS.8-Bromo Cyclic Adenosine Monophosphate: A long-acting derivative of cyclic AMP. It is an activator of cyclic AMP-dependent protein kinase, but resistant to degradation by cyclic AMP phosphodiesterase.Genitalia, Male: The male reproductive organs. They are divided into the external organs (PENIS; SCROTUM;and URETHRA) and the internal organs (TESTIS; EPIDIDYMIS; VAS DEFERENS; SEMINAL VESICLES; EJACULATORY DUCTS; PROSTATE; and BULBOURETHRAL GLANDS).Diethylhexyl Phthalate: An ester of phthalic acid. It appears as a light-colored, odorless liquid and is used as a plasticizer for many resins and elastomers.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Rats, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.Androstenedione: A delta-4 C19 steroid that is produced not only in the TESTIS, but also in the OVARY and the ADRENAL CORTEX. Depending on the tissue type, androstenedione can serve as a precursor to TESTOSTERONE as well as ESTRONE and ESTRADIOL.Steroidogenic Factor 1: A transcription factor and member of the nuclear receptor family NR5 that is expressed throughout the adrenal and reproductive axes during development. It plays an important role in sexual differentiation, formation of primary steroidogenic tissues, and their functions in post-natal and adult life. It regulates the expression of key steroidogenic enzymes.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Sperm Count: A count of SPERM in the ejaculum, expressed as number per milliliter.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.PhosphoproteinsAminoglutethimide: An aromatase inhibitor that is used in the treatment of advanced BREAST CANCER.Diethylstilbestrol: A synthetic nonsteroidal estrogen used in the treatment of menopausal and postmenopausal disorders. It was also used formerly as a growth promoter in animals. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985), diethylstilbestrol has been listed as a known carcinogen. (Merck, 11th ed)Progesterone: The major progestational steroid that is secreted primarily by the CORPUS LUTEUM and the PLACENTA. Progesterone acts on the UTERUS, the MAMMARY GLANDS and the BRAIN. It is required in EMBRYO IMPLANTATION; PREGNANCY maintenance, and the development of mammary tissue for MILK production. Progesterone, converted from PREGNENOLONE, also serves as an intermediate in the biosynthesis of GONADAL STEROID HORMONES and adrenal CORTICOSTEROIDS.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.