LH Gonadotrophs Research Articles

Cells Co-Expressing Luteinising Hormone and Thyroid-Stimulating Hormone Are Present in the Ovine Pituitary Pars Distalis but Not the Pars Tuberalis: Implications for the Control of Endogenous Circannual Rhythms of Prolactin

Background/Aims: A mammalian circannual pacemaker responsible for regulating the seasonal pattern of prolactin has been recently described in sheep. This pacemaker resides within the pars tuberalis, an area of the pituitary gland that densely expresses melatonin receptors. However, the chemical identity of the cell type which acts as the pacemaker remains elusive. Mathematical-modelling approaches have established that this cell must be responsive to the static melatonin signal as well as prolactin negative feedback. Considering that in sheep the gonadotroph is the only cell in the pars tuberalis which expresses the prolactin receptor, and that in other photoperiodic species the thyrotroph is the only cell expressing the melatonin receptor in this tissue, a cell type which expresses both proteins would fulfil the theoretical criteria of a circannual pacemaker. Methods: Pituitary glands were obtained from female sheep under short days (breeding season) and long days (non-breeding season) and double immunofluorescent staining was conducted to determine the prevalence of bi-hormonal cells in the pars distalis and pars tuberalis using specific antibodies to luteinising hormone-β and thyroid-stimulating hormone-β. Results: The results reveal that whilst such a bihormonal cell is clearly present in the pars distalis and constitute 4% of the gonadotroph population in this region, the same cell type is completely absent from the pars tuberalis even though LH gonadotrophs are abundantly expressed. Conclusions: Based on these findings, together with existing data, we are able to propose an alternative model where the gonadotroph itself is controlled indirectly by neighbouring melatonin responsive cells, allowing it to act as a pacemaker.

Gonadotrophin subunit and GnRH receptor gene expression in the pars distalis of the equine pituitary

In the horse, pronounced changes in fertility occur annually in response to photoperiod. However, the mechanisms regulating gonadotrophin synthesis and release in this species remain unclear. Here, we investigated the expression of gonadotrophin subunits and GnRH receptor (GnRH-R) mRNA in the pituitary glands of Thoroughbred horses during the breeding (BS) and non-breeding (NBS) season. Seasonal effects on the prevalence of gonadotrophs in the pars distalis were also examined. GnRH-R and common α-, LHβ- and FSHβ-subunit mRNA contents were determined by Northern analysis and the prevalence of LH–gonadotrophs assessed by immunohistochemistry in pituitaries from sexually active females (mares) in the BS, and sexually inactive mares in the NBS. These variables were then measured in castrated male horses (geldings). In mares, pituitary content of FSHβ mRNA was significantly higher in the NBS ( P < 0.01). Conversely, the content of common α-subunit mRNA was significantly higher during the BS ( P < 0.05). In contrast, GnRH-R and LHβ mRNA abundance were unaffected by season. Interestingly, whereas no seasonal effects were apparent on the number of LH–gonadotrophs/field, the proportion of LH cells (in relation to all other cells) was higher in BS than NBS animals ( P < 0.05); this resulted from an increased number of non-gonadotroph cells during the NBS ( P < 0.05). In geldings, no significant seasonal effects were detected for any of the variables investigated ( P > 0.05). These results reveal robust seasonal effects on common α-subunit and FSHβ gene expression in the pituitary of the mare, in the absence of detectable changes in the content of LHβ or GnRH-R mRNA.

Developmental changes in the hormonal identity of gonadotroph cells in the rhesus monkey pituitary gland.

To help elucidate the regulatory mechanism responsible for divergent gonadotrophin secretion during sexual maturation, we examined the gonadotroph population and hormonal identity of gonadotroph subtypes in pituitary glands of juvenile (age, 1.7 +/- 0.2 yr) and adult (age, 12.3 +/- 0.8 yr) male rhesus monkeys (Macacca mulatta). Serum LH and testosterone concentrations were, respectively, 3 and 7 times lower in juveniles than in adults, thus confirming the different stages of development. Immunohistochemistry revealed that the proportion of LH gonadotrophs in relation to the total pituitary cell population in the juvenile animals was significantly smaller than in the adults. In a subsequent study, double immunofluorescent labeling identified three distinct gonadotroph subtypes in both age groups: ones expressing either LH or FSH and another one expressing a combination of both gonadotrophins. Whereas the number of monohormonal LH cells per unit area was greater in the adults than in the juveniles, the number of monohormonal FSH gonadotrophs was remarkably lower. However, the proportion of FSH cells (whether mono- or bihormonal) within the gonadotroph population was similar between groups. Interestingly, the proportion and number of bihormonal gonadotrophs as well as the LH/FSH gonadotroph ratio were significantly greater in the adults than in the juveniles. Taken together, these data reveal that during the juvenile-adult transition period, not only does the pituitary gonadotroph population increase, but a large number of monohormonal FSH gonadotrophs are likely to become bihormonal. Because this morphological switch occurs when marked changes in plasma gonadotrophins are known to occur, it may represent an intrapituitary mechanism that differentially regulates gonadotrophin secretion during sexual development.

Gonadotroph-lactotroph associations and expression of prolactin receptors in the equine pituitary gland throughout the seasonal reproductive cycle

An interaction between gonadotroph and lactotroph cells of the pituitary gland has long been recognized in several species. The current study was conducted to investigate whether an association between gonadotrophs and lactotrophs occurs in mares and whether prolactin receptors are expressed within the pituitary gland of this species. The effects of both reproductive state and season on these variables were examined in pituitary glands obtained from sexually active mares in July (breeding season), sexually active mares in November (non-breeding season) and anoestrous mares in November. Pituitaries were dissected out immediately after death and immunofluorescent staining was carried out on 6 micrometer sections using specific antibodies to the LHbeta subunit, FSHbeta subunit, prolactin and prolactin receptor. Gonadotrophs were observed in both the pars distalis and pars tuberalis; although they appeared mostly as isolated cells, small groups of gonadotrophs were also identified in the pars distalis. In contrast, lactotrophs were observed only as clusters of cells exclusively in the pars distalis of sexually active and anoestrous mares in November and in most of the sexually active mares in July. A specific gonadotroph-lactotroph association was identified only between large isolated gonadotrophs and lactotroph clusters. Double immunofluorescent staining for FSHbeta and prolactin revealed a similar gonadotroph-lactotroph association to the one detected for LH gonadotrophs. No statistical difference in the gonadotroph:lactotroph ratio was observed as a result of changes in reproductive status or season. However, a tendency for a simultaneous decrease in the number of gonadotrophs and an increase in the number of lactotrophs was detected in anoestrous animals. Prolactin receptor immunoreactivity was found in the pars distalis, but not in the pars tuberalis, of sexually active (July and November) and anoestrous animals for both long and short forms of the receptor. No prolactin receptor co-localization for either form of the receptor was observed in LH or FSH gonadotrophs in either of the reproductive states examined during both summer and winter seasons. Furthermore, no significant difference was apparent in the proportion of cells expressing prolactin receptors between mares of different reproductive state or season. The specific anatomical association between gonadotroph and lactotroph cells and the expression of prolactin receptors in the equine pituitary gland indicate a potential role of prolactin in the regulation of gonadotrophin secretion. However, the absence of evidence for co-localization of prolactin receptors in LH or FSH cells does not support the hypothesis of a direct effect of prolactin on the gonadotroph as reported in a short day breeder. The results raise the possibility that, in horses, an intermediate regulatory cell may mediate the action of prolactin on gonadotroph function.

Evidence for attenuation of hypothalamic gonadotropin-releasing hormone (GnRH) impulse strength with preservation of GnRH pulse frequency in men with chronic renal failure.

To investigate the nature of putative disturbances in pulsatile gonadotropin (LH) secretion in men with chronic renal failure, we undertook blood sampling at 10-min intervals for 24 h in 9 hemodialysis-dependent uremic men and 16 community- and age-matched controls. Serum LH concentrations were measured in a 2-site immunoradiometric assay, which does not cross-react with free alpha or LH beta-subunit and correlates well with an in vitro Leydig cell bioassay. Deconvolution analysis was applied to calculate the number, amplitude, mass, and duration of spontaneous LH release episodes and simultaneously estimate the half-life of endogenous LH in each subject. We observed that: 1) the estimated half-life of immunoradiometric LH removal from plasma averaged 103 +/- 11 min in normal and 207 +/- 29 min in uremic men (P < 0.01); 2) the number of LH secretory bursts was slightly higher in uremic than healthy men (e.g. 20 +/- 2.2 vs. 15 +/- 1.0 secretory bursts/24 h, respectively; P = 0.05); 3) the mass of LH secreted per burst was approximately 50% lower in chronic renal failure than in health, namely 1.4 +/- 0.18 vs. 2.8 +/- 0.42 IU/L (P < 0.01); 4) the decrease in the mass of LH secreted per burst was not due to a decline in LH secretory burst amplitude, but rather an attenuation of LH secretory burst duration (4.8 +/- 0.35 min in uremic vs. 11 +/- 1.3 min in normal men; P < 0.001); 5) the mean 24-h serum immunoradiometric LH concentration was significantly higher in uremia at 5.7 +/- 0.68 vs. 3.6 +/- 0.41 IU/L in controls (P = 0.017); and 6) serum estradiol concentrations were increased in uremia, but total and free testosterone concentrations did not differ significantly between the two subject groups. In response to synthetic GnRH (10 micrograms, administered iv after the 24-h basal sampling period), the mean mass of immunoradiometric LH released within each calculated LH secretory burst was similar in uremic (n = 8) and normal (n = 21) individuals. We conclude that uremia is accompanied by a specific defect in the pulsatile mode of LH secretion, which is marked by an abbreviation of LH secretory burst duration and a consequent fall in the mass of LH secreted per spontaneous release episode. There is no overall decline in LH secretory pulse frequency or gonadotroph responsiveness to a submaximally effective dose of exogenous GnRH. Such findings are consistent with diminished hypothalamic GnRH impulse strength.(ABSTRACT TRUNCATED AT 400 WORDS)

Patterns of Leydig cell and LH gonadotroph activity, and plasma testosterone concentrations in the seasonally reproducing Schreibers' long-fingered bat (Miniopterus schreibersii)

Spermatogenesis in Schreibers' long-fingered bat from approximately 33 degrees S in South Africa was seasonal, and occurred in the 3 months (February-April) preceding ovulation. The ultrastructure of the Leydig cells indicated a period of increased steroidogenesis at this time, and plasma testosterone concentrations were elevated from March to May (10.3 ng/ml). The reproductive accessory glands were secretorily active between March and May, and copulation occurred at the end of this period of activity. Changes in LH-beta immunoreactivity suggest that the LH gonadotrophs were secretorily active 1 month before the onset of spermatogenesis and that peak activity coincided with peak plasma testosterone concentrations, spermiogenesis and spermiation. During winter (May-August) there was no reproductive activity and the bats remained active, only entering prolonged periods of torpor during particularly cold spells. A secondary elevation in plasma testosterone concentration, during reproductive inactivity (October; 9.3 ng/ml), was not accompanied by any change in Leydig cell ultrastructure, and the biological significance of this peak is unknown. Such synchronous activity of the pituitary, Leydig cells, seminiferous epithelium and accessory glands is associated with the typical reproductive cycle of long-fingered bats in which copulation and fertilization are restricted to a brief period at the end of summer, and in which neither sperm storage nor a prolonged period of copulation occur.

Interaction of endogenous chicken gonadotrophin-releasing hormone-I and -II on chicken pituitary cells.

The presence of two endogenous forms of gonadotrophin-releasing hormone (GnRH) in the chicken hypothalamus (chicken GnRH-I ([Gln8]GnRH) and chicken GnRH-II ([His5, Trp7, Tyr8]GnRH)), and the stimulation of gonadotrophins by both forms, suggests the possible existence of GnRH receptor subtypes and gonadotroph subtypes in the chicken pituitary. This question was investigated by assessing the effects of various combinations of the two known forms of chicken hypothalamic GnRH and antagonist analogues of GnRH on LH release from dispersed chicken anterior pituitary cells in both static and perifused systems. The relative inhibition of chicken GnRH-I-stimulated and chicken GnRH-II-stimulated LH release by 12 GnRH antagonists did not differ significantly, suggesting a single GnRH receptor type. Chicken GnRH-II was approximately sixfold more potent than chicken GnRH-I in releasing LH. Release of LH in response to maximal doses of chicken GnRH-I and chicken GnRH-II and to a mixture of both was similar and the two peptides were not additive in their effects, consistent with the presence of a single type of LH gonadotroph and a GnRH receptor which binds both forms of GnRH. Each form of GnRH desensitized cells to subsequent stimulation with the other form, providing additional evidence for a single type of LH gonadotroph. These findings suggest that chicken GnRH-I and -II stimulate gonadotrophin release through a single GnRH receptor type on a single class of LH gonadotroph in the chicken pituitary.

Influence of age on pulsatile luteinizing hormone release and responsiveness of the gonadotrophs to sex hormone feedback in men.

The influence of aging on serum LH and testosterone (T) pulse frequency and gonadotroph sensitivity to androgen and estrogen feedback was studied in young (less than 55 yr old) and elderly (greater than 65 yr) Trappist monks. LH pulse frequency (sampling interval, 20 min) was significantly lower [0.25 +/- 0.03 (+/- SEM) vs. 0.38 +/- 0.02 pulses/h; P less than 0.01] in elderly (n = 21) than in young monks (n = 27); the pulse amplitudes were similar. Similarly, T pulse frequency was lower in the elderly than in the young monks (0.13 +/- 0.04 vs. 0.23 +/- 0.02 pulses/h; P less than 0.01). In elderly men, the hypothalamo-pituitary complex was more sensitive to 5 alpha-androstan-17 beta-ol-3-one feedback, as determined by the decrease in serum LH and T levels. Moreover, during 5 alpha-androstan-17 beta-ol-3-one (125 mg/day, percutaneously, for 10 days) administration, the LH response to LHRH (100 micrograms, iv) was significantly higher in the elderly men compared to the pretreatment response. During estradiol (1.5 mg/day, percutaneously for 10 days) administration, the LH response to LHRH was decreased in the elderly men, but unchanged in the young men, suggesting greater responsiveness to estradiol in the elderly men. We conclude that in aged men, decreased testicular androgen secretion is not exclusively the consequence of a primary testicular alteration, but that important changes occur in hypothalamo-pituitary function, specifically decreased LH pulse frequency and increased LH responsiveness to sex hormone feedback.

A quantitative immunohistochemical study on the pituitary LH gonadotrophs in the female Afghan pika after copulation.

The female Afghan pika is known as a species of copulatory ovulators exhibiting persistent estrus unless copulatory stimuli are employed. The plasma LH concentration rose quickly after copulation, peaked at 6 h and descended thereafter until 12 h. Before copulation (estrus), immunoreactive LH-containing cells of the pituitary in this species were filled with numerous large electron dense secretory granules, but the Golgi apparatus and the granulated endoplasmic reticulum were not well developed. One hour later the stainability of the cells was faint, their secretory granules were malls in size and in number, and were of low electron density. These alterations were the most predominant at 12 h after copulation. No exocytotic extrusion of secretory granules was observed throughout the experiment.

Renin in the brain and neuroblastoma cells: an endogenous and intracellular system.

A major portion of renin-like activity in extracts of brain tissues is due to nonspecific action of proteases. True renin has been separated from the proteases by various affinity chromatographic methods and true renin was identified by its inhibition by specific antirenin antibodies. Brain renin has been purified to varying extents. Renin in bovine pituitary was completely purified. Certain properties of brain renin are different from renal renin. The presence of inactive prorenin was also found in many regions. Immunohistochemical studies with renin antibodies showed intracellular localization of renin in many regions of the brain. Renin was also localized in LH gonadotrophs in the adenohypophysis. Many cloned neuroblastoma cell lines contain not only renin but also all other components of the renin-angiotensin system, indicating the existence of an intracellular mechanism of angiotensin formation within neurons.

Development of the hypothalamic-hypophysial-gonadotrophic activities in fetal rats.

Pituitary responsiveness to LHRH and anti-LHRH serum was investigated in fetal rats aged 18.5-22.5 days. Synthetic LHRH injection in utero into fetuses brought about a remarkable depletion of pituitary-LH with a corresponding increase of serum-LH on day 18.5. On the contrary, anit-LHRH serum administration to day-20.5 fetuses caused a significant augmentation of pituitary-LH 1 day later. These data indicate that LH-gonadotrophs respond to LHRH even on day 18.5, and that endogenous LHRH begins to affect LH gonadotrophs on day 20.5.

Effect of cyproterone acetate on adenohypophysis of castrated mice.

Pituitaries from castrated male mice injected with cyproterone acetate were examined ultrastructurally. LH gonadotrophs showed two types: (a) those containing a dilated RER, a hypertrophied Golgi, and decreased granular content; and (b) those presenting an electron lucent cytoplasm and a nonhypertrophied RER. Following cyproterone acetate treatment both LH cell types showed increased RER cisternal hypertrophy and absence of Golgi membranes. In LH type (a) gonadotroph-increased granular content was noted. No detectable alterations were noted in FSH gonadotrophs following cyproterone acetate treatment. Cyproterone acetate may have stimulated the synthesis of the protein component but inhibited the incorporation of the carbohydrate moiety and LH release.

Prolactin immunoreactivity of acidophils of the small granule type.

The fine structure of some oval anterior pituitary cells of the adult male rats immunostained with an antiserum to rat prolactin was investigated electron microscopically on the adjacent thin sections. Their fine structural appearance is identical with that of acidophils of the small granule type (Yoshimura et al. 1974) resembling the Kurosumi-Oota LH gonadotrophs. The secretory granules of the oval cells are spherical in shape, ranging from 130 to 200 nm in diameter. Large polymorphic granules, which are generally believed to be characteristic of prolactin cells, are absent from their cytoplasm. It is concluded that the acidophil of the small granule type with a similar fine structure to the Kurosumi-Oota LH gonadotroph is a prolactin secreting cell.

Ultrastructure of rat pituitary LH gonadotrophs in relation to serum and pituitary LH levels following repeated LH-RH stimulation

The effects of single and repeated LH-RH injections at 120 min intervals on female rat LH gonadotrophs and on pituitary and serum LH levels were investigated using electronmicroscopy and radioimmunoassay. A temporary stimulation of granule release, of protein and new granule synthesis and of the accumulation of lysosomal structures was found in LH cells after the first LH-RH injection. The temporary stimulations were massively enhanced after the second injection. These consecutive yet in their time-sequence overlapping processes account for the initial depletion of secretory granule content (3--15 min after LH-RH injection), for the subsequent regranulation and accumulation of granules above control levels (60--120 min after injection) and also for the reduction in the number of granules to control levels (150 min after LH-RH injection and thereafter). Increased polymorphic lysosomal structures are believed to be responsible for this reduction of excess granules. The amount of assayable pituitary and serum LH generally corresponds with the morphological changes observed in LH-gonadotrophs, thus further substantiating the above observations. A schema which summarizes the observed morphological and hormonal changes in their time-sequence in response to LH-RH stimulation depicts the short-term regulation of secretory processes in female gonadotrophs.

Separation and maturation of gonadotrophs from 2A8 clonal cells in vitro

2A8 clonal cells derived from the epithlium of Rathke's pouch of fetal rats were cultured in growth medium supplemented with fresh rat serum, median-eminence extract and 1-thyroxine. Then, in order to isolate gonadotrophs, cyanogen bromide-activated Sepharose whichwas conjugated with LHRH (LHRH-Sepharose) was added to the culture medium. Fourteen days after incubation of 2A8 cells with LHRH-Sepharose, agranular and granular cells were rapidly bound to LHRH-Sepharose when fresh serum had previously been added in the medium. The cytoplasm of granular cells that were bound to LHRH-Sepharose contained spherical secretory granules (200-250 nm in diameter). These cells were similar in morphology to the FSH and LH gonadotrophs described by Kurosumi (1968). Moreover, many of them appeared as hypertrophied cells that resembled "castration" cells. These results demonstrate that LHRH conjugated to Sepharose can be used to separate gonadotrophs from other 2A8 cells, and it is suggested that the hypertrophy of some cells might be due to persistent stimulation by LHRH which is likely bound to receptors on the cell membrane.

The influence of severe illness on gonadotropin secretion in the postmenopausal female.

Severe weight loss in amenorrheic premenopausal women may significantly depress gonadotropin secretion. Gonadotropin leves were studied in 111 postmenopausal women to determine if weight loss and cachexia could similarly affect gonadotropin function. Thirty-three healthy ambulatory postmenopausal women and twenty-seven healthy hospitalized women admitted electively were found to have a wide range of elevated values, whose mean did not differ significantly. Mean levels for both LH and FSH were significantly suppressed (P less than .005) in severely ill postmenopausal women both with or without weight loss. (formula: see text) Recovety from illness in six patients was associated with a rapid rise in FSH levels while LH remained depressed. Two severely ill patients studied over a 6 h period revealed constant depression of both gonadotropins without the characteristic pulses seen in four normal control postmenopausal women. These results indicate that gonadotropin secretion may be suppressed in severely ill postmenopausal women whether weight loss is present of not, and the central nervous regulatory mechanism responsible for intermittant release of gonadotropins is impaired. The disparate FSH and LH recovery indicates that if separate gonadotrophs exist, the LH gonadotroph is more severely affected than the FSH gonadotroph and/or that the responsible regulatory mechanisms are different.

Effect of active and passive immunization with luteinizing hormone-releasing hormone on serum luteinizing hormone and follicle-stimulating hormone levels and the ultrastructure of the pituitary gonadotrophs in castrated male rats.

The effect of active and passive immunization with luteinizing hormone-releasing hormone (LHRH) on serum LH and follicle-stimulating hormone (FSH) levels and the ultrastructure of the pituitary gonadotrophs was investigated in castrated male rats. Two weeks after castration, the animals were immunized with Glu1-LHRH conjugated with human serum albumin (hSA), immunized with hSA only, or left uninjected. Immunogens were administered every 2 weeks. Four weeks after the initiation of immunization with hSA-Glu1-LHRH, 2 out of 4 rats showed parallel decreases in serum LH and FSH levels associated with a rise of serum antibody titer to LHRH. Serum LH and FSH levels remained suppressed throughout the experiment in these rats. On the other hand, both LH and FSH levels in hSA-immunized rats or non-immunized rats remained elevated, and typical castration cells containing large vacuoles were found in the pituitary. Although castration cells existed in the pituitary of rats which produced antibody to LHRH by active immunization, these cells were markedly degranulated, and secretory granules were scarce in the cytoplasm. In another experiment, rats were injected iv with one ml sheep anti-LHRH gamma-globulin (anti-LHRH) or normal sheep gamma-globulin (NSG) every 2 days for 3 weeks, starting one day after castration, when serum LH and FSH levels were already elevated. All the animals which received anti-LHRH showed a decrease in both serum LH and FSH levels, which remained low throughout the study, in a range comparable to those in intact normal male rats. On the other hand, in the animals which received NSG, both LH and FSH levels remained high or increased further throughout the experiment, and the pituitary contained numerous castration cells. Castration cells were completely absent from the pituitaries of rats treated with anti-LHRH, suggesting that castration cells are formed as a result of increased secretion of LHRH. Some FSH gonadotrophs in these castrated rats were atrophic. It was difficult to distinguish the LH gonadotrophs in rats which were either actively or passively immunized with LHRH; however, they seem not to have contributed significantly to the development of castration cells. In any case, antibody to the LHRH decapeptide drastically affected both LH and FSH cells, providing additional evidence for the concept that LHRH represents the physiological LHRH and FSHRH.

Effect of Anti-Luteinizing Hormone Antibodies on the Gonadotropic Cells of the Pituitary in Immature Male Rats: An Electron Microscopic Study

Treatment of immature rats with antigonadotropic serum results in atrophy of gonads and castration-like changes of gonadotroph cells in the pituitary gland. Newborn male albino Wistar rats were daily and subcutaneously inoculated with 0.1 to 0.8 ml of anti-luteinizing hormone (LH) sera from the first 24 hours of age, through the first 5 weeks. For controls, a similar schedule with normal rabbit serum was used. Rats were killed at weekly intervals and pituitaries were fixed for electron microscopy. The anti-LH titer, determined by microhemagglutination, was between 1:2, 560 and 1:10,240; the greatest contaminant was follicle-stimulating hormone, with the antiserum ranging from 1:160 to 1:320. Absorbed antisera, checked by double agar diffusion against unabsorbed antisera, showed no precipitin lines, indicating no antigen excess. There was no significant cytologic difference between control and experimental pituitaries during the 1st week of treatment. At the end of the 2nd week, gonadotroph cells contained a highly developed Golgi complex; by the 3rd week these cells contained pronounced, dilated, saclike ergastoplasmic cisternae, with few secretory granules in the cytoplasm of one type; by the 4th week, ergastoplasmic cisternae had broken down to form the first large vacuoles of "castration" LH gonadotrophs, some of which contained typical granules. Numerous mitotic and chromophobe cells were also observed. At the end of the 5th week castration LH cells persisted, in addition to mitotic cells, chromophobes, and numerous follicle-stimulating hormone gonadotrophs with degenerated features. The effect of anti-LH antisera on pituitary gonadotrophs could be explained as a neutralization of endogenous LH, probably not only inhibiting the long feedback mechanism, but also the short feedback loop at the level of the same pituitary cells.

Effects of chronic treatment with LH-FSH-RH in hypophysectomized pituitary-grafted male rats.

The effect of a prolonged treatment with LH/FSH—RH was studied in long—term hypophysectomized male rats bearing pituitary grafts under the kidney capsule. LH/FSH—RH was injected twice a day in 1.5% gelatin solution and control rats were injected with the vehicle alone. Two months later the animals were sacrificed. Control rats showed marked regression of spermatogenesis and only prolactin cells seemed to be active when electron microscopic observations of the pituitary grafts were made. Detectable serum FSH and LH levels were present, however, in these animals. The rats injected with LH/FSHRH showed a striking stimulation of spermatogenesis, with complete spermiogenesis in some cases. Electron microscopy of the pituitary grafts showed a predominance of prolactin cells and FSH gonadotrophs; the latter appeared to be functionally active, in contrast to the FSH cells of control grafts. The LH gonadotrophs showed variable numbers of secretory granules, but, in general, these cells were smaller than those of n...

Immunofluorescent localization of the LH cell of the human adenohypophysis.

ABSTRACT The LH producing cell of the human adenohypophysis has been identified by the immunofluorescent technique followed by aldehyde thionin-periodic acid Schiff-orange G (AT-PAS-OG) staining. It is a basophilic subtype with sparse granularity which is both PAS and aldehyde thionin-positive. These cells occur singly throughout the gland and are found in many shapes and sizes but are usually angular and rather small. They have been named the LH gonadotrophs. The ovoid AT-positive delta I gonadotroph was not stained by the anti-HCG used to identify the LH cell; it may be the source of FSH, but this remains to be ishown by similar immunological localization of anti-human FSH.