Pituitary gland of the garter snake (Thamnophis): Morphology and immunocytochemistry

The three-dimensional gross morphology of the pituitary gland of the garter snake (Thamnophis sirtalis) is presented. Hormone-producing cells of the pars distalis were localized immunocytochemically. Corticotropes and lactotropes occur in the anterior two-thirds of the gland; corticotropes are especially numerous in the area of the pars distalis nearest the median eminence, and lactotropes are most abundant medially. Somatotropes are restricted to the posterior one-third of the pars distalis. Gonadotropes and thyrotropes are scattered throughout the pars distalis and in favorable sections form a network of cells enclosing clusters of peptide-secreting cells.     

An immunocytochemical study of human pituitary mammotropes from fetal life to old age.

The objectives were to (a) describe the cytology and distribution of mammotropes in the human pituitary gland, (b) determine whether the mammotrope is a distinctive secretory cell type and (c) ascertain when it first appears in the fetal hypophysis. Identification of mammotropes was based primarily on the Sternberger peroxidase-antiperoxidase immunocytochemical method used with an antiserum to human prolactin. Hypophyses from 25 male and 6 female adults, and 21 fetuses ranging in gestational age from 6 to 23 weeks were studied. In the adult two morphological forms of mammotropes were observed. Mammotrope I possessed a small perikaryon that commonly was located centrally in parenchymal cell cords. From the perikaryon long cytoplasmic processes extended toward neighboring capillaries. Mammotrope I reached its highest incidence in the posterolateral zones of the pars distalis. Mammotrope II possessed a larger perikaryon with short processes; cells of this form were fewer and occurred chiefly in the anteromedian zone. Mammotropes with intermediate morphological features that prevented classification into categories I or II were common in some hypophyses. Both forms of mammotropes were present prepuberally (one 6-week and one 9-year-old male) and in adult males and females. Mammotropes were only slightly more prominent in females than males. Regression of mammotropes was evident in old age. Mammotropes were distinctly different from somatotropes, corticotropes, gonadotropes and thyrotropes. In the fetal hypophysis mammotropes appeared first at 14 weeks of gestational age and remaind few through 16.5 weeks. Their number increased greatly at 23 weeks.     

The genesis of cell types in the adenohypophysis of the human fetus as observed with immunocytochemistry.

Hypophyses of 21 human fetuses, ranging in gestational age from 6 to 23 weeks, were studied by immunocytochemical and histological staining to ascertain (1) the time of origin of specific cell types and (2) the development of parenchymal cell zonation in the pars distalis. No hormones were identified at six weeks. Probable corticotrophin-containing cells appeared at seven weeks. Somatotrophs were observed first at 10.5 weeks; correlation with other reports indicates that they appear at eight to nine weeks. Melanotrophs were detected at 14 weeks; the cells containing melanotrophin were far fewer than corticotrophs. The youngest fetus to possess gonadotrophs was 10.5 weeks old. In all specimens gonadotrophs (LH-cells) stained well with immunocytochemical procedures but poorly with histological methods. Thyrotrophs first occurred at 13 weeks. Zonal distribution of cell types in the pars distalis was evident almost from the time of their appearance. Somatotrophs were most numerous laterally and immediately anterior to the residual cleft. At 10.5 weeks corticotrophs were confined chiefly to the borders of vascularized connective tissue (trabeculae) and to the lateral peripheral region of the pars distalis. Thyrotrophs appeared chiefly in the anteromedian zone, particularly in its superior portion, but were found laterally also. In the older specimens, gonadotrophs generally occurred throughout the pars distalis but were less numerous near the trabeculae and in the anterolateral region. There was good correlation between the time of appearance of various cell types and published data on secretory capacity of the gland.     

Demonstration of gonadotropic cells in the adenohypophysis (pars distalis and pars tuberalis) of the monkey Macacus irus. Immunofluorescence study using human anti-beta-FSH and ovine anti-beta-LH antibodies

Indirect immunofluorescence technique with anti-beta FSH and anti-beta oLH antisera has allowed us to detect "gonadotropic cells" in the pars distalis and in the pars tuberalis of the adenohypophysis of the monkey Macacus irus. In the pars distalis, 85-90 % of the "gonadotropic cells" react simultaneously with these two antisera ; 10-15 % of these cells react only either with anti-beta hFSH or anti-beta oLH antisera. The gonadotropic cells are dispersed in the whole pars distalis, amid the other cellular types ; indeed, in the female, there is a "gonadotropic zone" in the median zone of the lateral lobes of the gland. In the pars tuberalis, we have observed "gonadotropic cells" which react only with anti-beta oLH antiserum. These results are compared with observations of some authors.     

Immunocytochemical studies on the pituitary pars distalis of the Japanese long-fingered bat,Miniopterus schreibersii fuliginosus

Summary Immunocytochemical studies were performed to describe the characteristics of cell types and their distribution in the pars distalis of Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, collected at various stages of the reproductive cycle. Six distinct cell types have been identified in the pars distalis by the unlabeled immunoperoxidase technique and by the ABC method. Growth hormone (GH) and prolactin (PRL) cells were immunostained with antisera against chicken GH and ovine PRL. The GH-immunoreactive cells were round or oval orangeophilic cells distributed throughout the pars distalis with prominent aggregation in the posterolateral region. The PRL cells were pleomorphic carminophilic cells that occurred in small groups within the central and dorsocaudal regions of the pars distalis. They were sparsely distributed in the central region of the pars distalis in the hibernating bats, but increased significantly in the pregnant and lactating bats. The adrenocorticotropic (ACTH) cells were large round or polygonal amphophilic cells in the rostroventral and ventrolateral regions of the pars distalis. The thyrotropic (TSH) cells were small rounded or polygonal and distributed mainly in the ventrolateral region of the pars distalis. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) cells were identified immunocytochemically with antisera against the specific beta subunits of ovine LH and rat FSH. There were two populations of LH and FSH cells, one aggregated in the zona tuberalis and the other scattered singly throughout the rest of the pars distalis. The aggregated cells were immunoreactive with both antisera directed to LH and FSH, while scattered cells were reactive solely with antiserum to either LH or FSH and exhibited seasonal variations. In females, the proportional volume of the pars distalis occupied by LH cells was significantly reduced during pregnancy and lactation. No evidence of involution was observed in pars distalis cells except for PRL cells in males or females during hibernation.     

An immunohistochemical study of adenohypophyseal cells in the viviparous reptile Chalcides chalcides

The morphology of the hypophysis and the immunocharacteristics of the adenohypophyseal cells in the viviparous reptile Chalcides chalcides were studied by light microscopy, using conventional staining methods and an indirect antibody technique (ABC method), respectively. The general morphology of the C. chalcides hypophysis was comparable to that of other reptiles, showing three main regions: the pars distalis, the pars intermedia and the pars nervosa. The gland appeared as an elongated body in a cephalic-caudal direction and was almost completely enclosed in the sella turcica. For this reason, the hypophysis was studied in toto with the brain in decalcified specimens. The pars distalis accounted for most of the whole organ. The pars intermedia surrounded the pars nervosa as a goblet. The pars tuberalis was lacking.The immunohistochemical identification of the adenohypophyseal cells was performed using rabbit antisera against mammalian/synthetic hypophyseal hormones. Prolactin cells were clustered in small cellular cordons in the rostral pars distalis and in the medial pars distalis in both male and female specimens. Somatotropic cells were found in the caudal pars distalis. Corticotropic cells were observed in the medio-rostral pars distalis, as well as in the pars intermedia, where melanotropic cells were also present. Melanotropic cells were confined to the pars intermedia. Gonadotropic cells were mostly distributed in the ventral and lateral portions of the pars distalis, where they were found isolated or in small clusters. Thyrotropic cells were detected in the pars distalis with a distribution similar to that of the gonadotropic cells; however, atypically, they were also found in the pars intermedia. Therefore, the cytological characteristics of the adenohypophyseal cells appeared mostly conserved.     

The influence of social rank on adenohypophysial cell activity in Salmo irideus

Summary In nine cell types of the adenohypophysis in untreated adult rainbow trout, histologically different activity phases, seasonal changes in activity, and the relation between certain cell types and the interrenal gland, thyroid or gonads were investigated by light and, occasionally, by electron microscopy. Special attention was given to the effect of social rank on the synthetic activity in adenohypophysial cells of trout kept in small groups in which a social hierarchy with one (light) dominant and several (dark) submissives is established.Cell types in the rostral pars distalis were azocarminophil (I) or amphiphil (II). Proximal pars distalis cell types were slightly basophil (IV), orangeophil (V), strongly basophil (VI) or chromophobe (VII). In the pars intermedia, cell types were amphiphil (VIII) or very slightly basophil (IX). Type III was a non-secretory supporting (?) cell.Histologically different activity phases abounded in type IV cells, which mainly occurred in the proximal pars distalis but were also found dispersed in the rostral pars distalis, the pars intermedia and the neurohypophysis.Influences of social rank were pronounced in type IV cells. Phases with a high synthetic activity were exclusively found in submissive animals, phases with a low synthetic activity occurred in dominants. As a positive relation existed between type IV cell activity and the social rank dependent activity of the interrenal gland, it was suggested that type IV cells produce ACTH.In (dominant) male trout treated with DOCG or ACTH, colloid-containing type IV cell phases, reflecting accumulation of the secretory product, were found. This supported the earlier suggestion that ACTH in the trout is produced in the basophil type IV cells and not, as reported in the literature, in cells comparable to type II.The author is greatly indebted to Miss M.C. Wentzel, Miss I. Stulen, Mr. J. Veening and Dr. J.G. van Rhijn for their help with histological techniques, interrenal cell measurements and statistical aspects     

The Cell Types in the Adenohypophysis of the Marine Teleost Crenilabrus melops

Sagittal sections from pituitaries of winter and spring fish were stained with a number of methods including alcian blue-PAS-orange G, Herlant's tetrachrome, Luxol fast blue-PAS-orange G and lead haematoxylin. By these methods seven different endocrine cell types were readily demonstrated in the adenohypophysis. In the rostral pars distalis (RPD), there were conspicuous vacuoles (intra- and possibly extracellular) in the prolactin cell zone of all animals. The ACTH cells in the RPD were very numerous. In the proximal pars distalis (PPD), the growth hormone cells were arranged in coiling bands that were predominantly dorsal and juxtaposed to neurohypophysis. Two types of basophils were readily distinguished: both were predominantly ventral in the proximal pars distalis, though the type I basophil also formed a constant group in the dorsal region of the pituitary, between the PPD and the RPD. The pars intermedia contained two cell types — a lead haematoxylin-positive cell and a PAS-positive cell. The pituitary morphology is compared with that of other teleosts.     

A histological study of the hypophysial-gonadal system during sexual maturation and spawning in the milkfish, Chanos chanos (Forskal)

The pituitary gland of the milkfish, Chanos chanos , was studied at different stages of sexual maturation and spawning. Consecutive median sagittal sections were treated with a range of stains to demonstrate the different cell types and regions. The milkfish pituitary consists of a neural component, the neurohypophysis, and an epithelial component, the adenohypophysis, which in turn consists of three regions: the rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). However, unlike most teleosts, the pituitary gland of the milkfish is encased in a bony chamber, has dorsal and ventral lobes and extends anteriorly from its point of origin at the base of the brain. PAS (+) basophils are found in all regions of the adenohypophysis, but mostly in the proximal pars distalis. These cells undergo hypertrophy and hyperplasia during sexual maturation, shrinkage and degranulation during spawning.     

Occurrence of colloid-containing follicles and ciliated cysts in the hypophysial pars tuberalis from guinea pigs of various ages

Colloid-containing follicles and ciliated cysts in the hypophysial pars tuberalis of guinea pigs at various ages ranging from 5 days to 36 months were examined by periodic acid-Schiff (PAS) reaction, immunohistochemistry, and electron microscopy. The follicles storing PAS-positive colloid were encountered in the pars tuberalis of all guinea pigs examined, although only a few were present in young animals. The follicles gradually increased in number with age. The largest number of follicles was found in the senile male group: 141.3 +/- 11.9, about 10 times the number in the 5-day-old male group. The follicles were scattered throughout the entire length of the pars tuberalis. Follicles with enlarged luminal cavities were concentrated in the ventral caudal region surrounding the infundibular stem and merges with the pars distalis. Three different types of follicles were found by electron microscopy: 1) those surrounded by nongranulated follicular cells that may correspond to the stellate-follicular cells in the pars distalis, 2) those surrounded by specific cells that were packed with vesicular inclusions, and 3) those surrounded by granulated cells that may be gonadotropes. In the follicles lined by non-granulated follicular cells, long, prominent microvilli and cytoplasmic processes protruding into the lumen and invaginations of colloid were often observed at the apical cell region. The follicles lined by the specific cells having numerous vesicles were localized only in the ventral caudal portion. The vesicles ranged from 200 to 700 nm in diameter, and the outer surface of their limiting membrane was partly studded with ribosomes. Gonadotropes immunoreactive to the luteinizing hormone (LH) and follicle-stimulating hormone (FSH) antisera were distributed in the guinea pig pars tuberalis. As well as the typical follicles described above, the follicles composed solely of granulated cells showed microvilli protruding into the cavities and junctional complexes at the apical lateral surface. They stored heterogeneous materials in the lumina. Some secretory granules gave the appearance of being discharged into the lumen. Ciliated cysts were frequently observed in the pars tuberalis; their incidence was 71.7%. The ciliated cysts were much larger than colloid-containing follicles. Cystic cavities were only partly filled with heterogeneous materials showing colloid-like, flocculent, and granular features.     

乌龟脑垂体显微及其腺垂体超微结构的研究

乌龟脑垂体由柄形神经垂体和椭圆形腺垂体两部分组成,神经垂体位于腺垂体后部上方呈背腹型排列。神经垂体中神经叶不发达,腺垂体分为远侧部和中间部,特殊空泡结构成为垂体门脉系统的特征。远侧部细胞分为嗜酸性细胞、嗜碱性细胞和嫌色细胞3种。通过透射电镜观察,腺垂体远侧部主要有5种分泌激素细胞:即生长激素(GH)分泌细胞、催乳激素(PRL)分泌细胞、促甲状腺激素(TSH)分泌细胞、促肾上腺皮质激素(ACTH)分泌细胞、促性腺激素(GTH)分泌细胞和非分泌类型滤泡-星形细胞(FS)。生长激素分泌细胞核大、分泌颗粒少的特征成为乌龟与其他动物最大的区别,可能与乌龟具有生长慢、寿命长的生物学特性有关。       

Developmental correlation between hypothalamic somatostatin and hypophysial growth hormone

Summary The objective of the present study was to determine, by means of immunocytochemistry, the age in fetal development at which GH is first detectable in the pituitary gland and somatostatin in the median eminence, and to correlate temporally the development of these two hormones throughout the remainder of pregnancy. Mice were studied at 15–19 days of gestation with the peroxidase-antiperoxidase (PAP) technique of Sternberger. Somatotropes in the pars distalis were initially detected at 16 days of gestation and by 17 days they were a prominent component of the parenchymal cell population of the hypophysis. These cells were ovoid and distributed uniformly throughout the pars distalis; many were located adjacent to sinusoidal capillaries. Their number and staining intensity increased by 19 days. Somatostatin was not consistently observed in the median eminence until 19 days of gestation. Reaction product indicative of the presence of somatostatin in presumptive nerve endings was located on the ventral surface of the median eminence and in the external lamina of the infundibulum in proximity to the superficial portal capillaries. Results of the present investigation support the concept that the potential for neuroendocrine control of GH secretion exists in the mouse by the end of fetal development. Several hypotheses concerning the temporal relationship between the appearance of somatostatin in the hypothalamus and of GH in the anterior pituitary gland are discussed.Supported by a Biomedical Research Support Grant (NIH RR 5417). Appreciation is extended to the National Pituitary Agency, NIAMDD for the following radioiodination-grade hormones: hGH, rPRL, rTSH, rFSH and hCG     

乌脑龟垂体显微及其腺垂体超微结构的研究

乌龟脑垂体由柄形神经垂体和椭圆形腺垂体两部分组成,神经垂体位于腺垂体后部上方呈背腹型排列。神经垂体中神经叶不发达,腺垂体分为远侧部和中间部,特殊空泡结构成为垂体门脉系统的特征。远侧部细胞分为嗜酸性细胞、嗜碱性细胞和嫌色细胞3种。通过透射电镜观察,腺垂体远侧部主要有5种分泌激素细胞：即生长激素（GH）分泌细胞、催乳激素（PRL）分泌细胞、促甲状腺激素（TSH）分泌细胞、促肾上腺皮质激素（ACTH）分泌细胞、促性腺激素（GTH）分泌细胞和非分泌类型滤泡．星形细胞（Fs）。生长激素分泌细胞核大、分泌颗粒少的特征成为乌龟与其他动物最大的区别,可能与乌龟具有生长慢、寿命长的生物学特性有关。     

Seasonal changes in the pituitary gland of the feral hawaiian mongoose (Herpestes auropunctatus)

The Hawaiian mongoose (Herpestes auropunctatus) is a seasonally breeding mammal whose pituitary gland resembles that of other Viverridae. Certain features, such as a prominent pars tuberalis interna and a double-layered pars intermedia forming a cup for the neurohypophysis, are unique. With the light microscope, five different cell types can be recognized in the pars distalis after staining with periodic acid-Schiff (PAS)-orange G. Two types of acidophils are seen, a small yellow-staining cell and a large angular orange cell. Two basophilic cells are also seen, one with fine PAS-positive cytoplasmic granules and the other with coarse PAS-positive granules in the cytoplasm. The last cell type seen is the chromophobe. Differential cell counts indicated an altered distribution of chromophils in the ventral pars distalis of the female mongoose with changing season and reproductive status, but the most striking change was a decreased percentage of basophils in the pars distalis during the nonbreeding season.     

Cytological changes in hypophysis of immatur rats after administration of anti-LH antibodies (author's transl)]

In the present work, cytological changes produced in rats' pars distalis were studied by administration of anti-LH antibodies. The anti-LH sera was obtained by active immunization of adult rabbits using bovine LH hormone with Freund's complete adjuvant. Newborn albino Wistar male and female rats were daily and subcutaneously inoculated with 0.1 ml. to 0.8 ml of anti-LH sera from the first 24 hr. on during 5 weeks. For controls, a similar schedule of inoculations with normal rabbit serum was used. At weekly intervals during the treatment, 5 lots of rats were sacrificed and the rest after a recovery period of 95 days. At the end of the 2nd week of immunization, both male and female animals showed degranulated gonadotroph cells in the central part of the pars distalis; at the 3rd week these cells were hypertrophied and presented developed Golgi complex. At the 4th week, the first large vacuoles of "castration" were seen in the gonadotroph cells of male pars distalis, besides in the females the degranulation of gonadotrophs continued. During the last week of treatment, the gonadotrophs of the male animals presented a highly dilated Golgi complex, more "castration-like cells" and numerous mitosis figures. The gonadotrophs of females pars distalis presented degranulation, but not vacuoles. After the recovery period the gonadotrophs of male rats were similar to those of the control hypophisis and did not show castration vacuoles in their cytoplasm. In female rats, the gonadotrophic cells showed "castration-like vacuoles" and a raised number of mitosis cells compared to control pituitaries. The significance of these findings will be discussed.     

Seasonal variations in pituitary LH-gonadotropes of the hibernating bat Myotis lucifugus lucifugus: an immunohistochemical study

Pituitary gonadotropes were identified throughout the year in the seasonally breeding, hibernating bat Myotis lucifugus lucifugus by means of light microscopic immunohistochemistry. In both male and female bats, these cells were immunoreactive with an antiserum directed to the beta subunit of luteinizing hormone. Some gonadotropes were aggregated near a portion of the infundibular stalk which crosses the anterior lobe, while most were scattered singly in a uniform manner throughout the rest of the pars distalis. This cell population exhibited seasonal variations in both sexes. In males, the proportional volume of the pars distalis occupied by immunoreactive gonadotropes (volume fraction) was significantly reduced in late July, when plasma testosterone levels were approaching their seasonal peak. In females, the volume fraction declined in April, following ovulation, and remained low during pregnancy and lactation. The size and shape of gonadotropes appeared relatively constant throughout the annual reproductive cycle in male bats; the immunoreactive cells were irregular in shape, with cytoplasmic extensions insinuating between and often "cupping" other secretory cell types. In females, the gonadotropes resembled those of males throughout most of the year, except during pregnancy, when these cells became enlarged and ovoid. No evidence of involution was observed in these anterior pituitary cells in either males or females during hibernation.     

Ontogenesis of corticotropes and lactotropes in situ in the pituitary gland of the hamster

Summary The development of corticotropes and lactotropes was investigated in the golden Syrian hamster using an anti-porcine ACTH antiserum and a homologous antihamster PRL antiserum. Oval corticotropes were first visible in the ventral region of the pars distalis at 13 days of gestation. By the end of gestation, corticotropes were found throughout the pars distalis and in the pars intermedia. Corticotropes in the pars distalis of postnatal hamsters were either round or irregularly-shaped, often appearing in clusters. Throughout development, corticotropes often appeared to be surrounding other cells. Scarce, very small lactotropes were first observed in the pars distalis of hamsters on the first postnatal day. The number of these cells, which were either round or polyhedral, increased dramatically between 4 and 20 days of postnatal life. These observations indicate that the sequence of appearance of corticotropes and lactotropes in the hamster is similar to that in other species and that lactotropes are confined to the pars distalis of postnatal hamsters.     

Ultrastructure of the pars distalis of the lizard Anolis carolinensis with special reference to the identification of the gonadotropic cell

Summary Five categories of granulated cells were distinguished by their ultrastructural features, and quantitative analyses were made of the pars distalis cells in normal and castrated lizards. The gonadotropin-producing cell was identified on the basis of its uniform distribution in the gland as well as from cytological changes resulting from castration. The secretory granules of the gonadotropic cell vary in size (100–500 m) and density, and lipid bodies are commonly present. Following castration, the endoplasmic reticulum proliferates, forming many small, rough-surfaced, dilated cisternae which do not coalesce greatly as in other vertebrate species. Degranulation is accompanied by hypertrophy and hyperplasia of the mitochondria and by the appearance in the cytoplasm of conspicuous clusters of microfilaments. The designated gonadotropic cell was the only class of secretory cell showing consistent changes following three weeks of castration.In addition to the uniformly distributed gonadotrope cell, two secretory cells occur mainly in the rostral half of the gland, and two in the caudal half. Tentative identification of the cell types is discussed in the light of available information on the localization of the hormones in the pars distalis of this species.Grateful recognition is given to the Electron Microscope Laboratory of the University of California, Berkeley, for use of their facilities, and to Emily Reid for her assistance with the illustrations.Member of Consejo Nacional de Investigaciones Cientificas y Técnicas.     

Immunohistochemical identification of cells in the pars distalis of the pituitary of the lizard Anolis carolinensis

Immunocharacteristics of the pars distalis cells of the pituitary of the male lizard A. carolinensis are determined by employing the immunoperoxidase technique with antisera to mammalian pituitary hormones. On the basis of their immunoreactivity, 5 different cell types with characteristic anatomical distribution are recognized. ACTH cells are found in the rostral half of the pars distalis, and PRL cells in the rostral two thirds of the pars distalis. GH and TSH cells are located in the caudal half of the pars distalis. GTH cells are distributed throughout the gland. When consecutive sections are stained with antiserum to ovine FSH or its beta-subunit and to ovine LH, the same cells show immunoreactivity to all the three antisera. None of the GTH cells show positive immunoreactivity to ovine beta-LH antiserum. The results suggest the existence of one gonadotropic cell type in the pituitary of this lizard.     

Uptake and retention of sex steroids by the baboon pituitary gland--evidence of sexual dimorphism with respect to dihydrotestosterone

The localization and identification of the target cells for estradiol (E2) and dihydrotestosterone (DHT) were studied in the pituitary gland of male and female baboons (Papio cynocephalus) using autoradiography and autoradiography combined with immunocytochemistry. The largest number of cells which sequestered 3H-E2 were located in the pars distalis of both the males and females. Immunocytochemistry revealed that these target cells were predominantly gonadotrophs and mammotrophs, albeit a few somatotrophs and thyrotrophs were also labeled. A distinct sexual dimorphism was not observed with respect to the uptake and retention of the tritiated estrogen but was clearly evident in those animals given 3H-DHT. Significantly more cells in all three lobes of the male baboon, the partes distalis, intermedia and nervosa, concentrated the radiolabeled androgen as compared to that found in the females. Regardless of sex, however, the gonadotrophs were the major cell type in the pars distalis which was labeled. A small population of mammotrophs, somatotrophs and thyrotrophs also retained 3H-DHT. In both males and females, the pars nervosa was the portion of the hypophysis most sensitive to 3H-DHT. These findings indicate that all three lobes of the hypophysis of the male and female baboon contain target cells for E2 and DHT and that the propensity for DHT uptake is greater in males than in females.