Calcitonin immunoreactive cells in prostate gland and cloacal derived tissues

A Calcitonin-Producing Neuroendocrine Tumor of the Larynx: A Case Report

A moderately differentiated neuroendocrine carcinoma of the larynx is described. Although the patient had normal serum calcitonin level 36 months before, its level was elevated at the time the neck node was removed. This study supports the hypothesis that a diagnosis of calcitonin-producing neuroendocrine tumor of the larynx with increased plasma calcitonin is possible and should be considered to avoid unnecessary thyroidectomy.

Prostatic neuroendocrine tumor in multiple endocrine neoplasia Type 2B

We report the unusual occurrence of a neuroendocrine prostatic tumor in two young males with multiple endocrine neoplasia (MEN) 2B. Immunohistochemistry of the tumor markers may help differentiate a primary neuroendocrine prostate tumor from the metastasis of a medullary thyroid carcinoma of poor prognosis. MEN 2B hallmarks (i.e. plasma thyrocalcitonin and urinary metanephrines) may be systematically investigated in neuroendocrine tumors of the prostate, and conversely prostate examination may be performed in the periodic screening of MEN 2B male patients.

Incidence of neuroendocrine cells in the seminal vesicles and the prostate--an immunohistochemical study

INTRODUCTION

Prostate and seminal vesicles (sv) are both androgen-dependent male sex accessory glands. The cancer incidence in these two organs is vastly different. Neuroendocrine (NE) cells are involved in the regulation of prostate growth, differentiation and in prostate cancer carcinogenesis. Thus, knowledge of the incidence of NE cells in sv may add to our understanding of prostate cancer etiology.

METHODS

Samples of histologically confirmed normal prostate tissue and normal sv tissue from 20 men were immunostained for chromogranin A. The incidence of stained cells was evaluated semiquantitately.

RESULTS

Neuroendocrine cells were detected in all prostate specimens, but not a single stained cell was found in any of the sv specimens.

CONCLUSIONS

The lack of NE cells and, subsequently, of biogenic amines, peptides and growth factors may be a reason for the low cancer incidence in the seminal vesicles. Alternatively, the absence of NE cells can be seen as a hint that the stem cells of the prostate and sv react differently to endogenous and exogenous stimuli, and thus in the seminal vesicles, stem cells are not transformed into NE cells.

Presence of neuroendocrine cells during postnatal development in rat prostate: Immunohistochemical, molecular, and quantitative study

BACKGROUND

This work was undertaken to study the prostate neuroendocrine cells (PNEC) during the post-natal development of rats.

METHODS

Forty male Wistar rats (pre-pubertals, pubertals, young, and aged adults) were used for immunohistochemistry of chromogranin A (cgA), serotonin (SER), and protein gene product 9.5 (PGP9.5). They were also evaluated for numerical cell density (NV SER) and PNEC number per prostate (N SER). Five additional young adult rats were used for a RT-PCR study (mRNA cgA detection).

RESULTS

Weak immunoreactivity to cgA was observed in pubertal rats. No PNEC immunostained to PGP 9.5 was observed. Cells expressing SER were detected in all the groups exclusively located in periurethral ducts. The NV SER increased significantly in pubertal animals. In aged animals, it decreased to levels observed in pre-pubertal rats. The N SER increased significantly from pre-pubertal to young adults, decreasing in aged adults. There was weak production of cgA mRNA, with more expression in the dorsal prostate.

CONCLUSIONS

PNEC differ in rats when compared to humans: they are weakly immunopositive to cgA, do not express PGP 9.5, only show immunoreactivity to SER, and do not appear in acini. The changes in the amount of rat PNEC during the post-natal development suggest an androgenic influx. PNEC might regulate the contractility of periurethral ducts.

Neuroendocrine differentiation in prostatic carcinoma

BACKGROUND

Information is presented on prostatic neuroendocrine cells and neuroendocrine differentiation in prostatic carcinoma. The prognostic and therapeutic implications of neuroendocrine differentiation in prostatic carcinoma are reviewed.

METHODS

Data are presented that support the intriguing link between neuroendocrine differentiation, tumor progression, and androgen-independent prostate cancer. The hormones, and the receptors, expressed by prostatic neuroendocrine cells are investigated in order to elucidate their significance for prognosis and therapy.

RESULTS

The prognostic significance of neuroendocrine differentiation in prostatic malignancy has been controversial, but recent studies employing markers such as chromogranin A and neuron-specific enolase suggest that neuroendocrine differentiation, as reflected by increased tissue expression and/or blood levels of these neuroendocrine secretory products, correlates with poor prognosis, tumor progression, and androgen-independence. Since all malignant neuroendocrine cells are devoid of androgen receptors and since neuroendocrine phenotypic expression is not suppressed by androgen ablation, clonal propagation of androgen receptor-negative neuroendocrine cells may play an important role in the pathway towards the androgen-independent state of prostatic carcinoma. This would have significant implications for the treatment of prostate cancer, as several of the hormones known to be expressed by neuroendocrine-differentiated, malignant prostatic cells are potential candidates for drug therapy. A limited number of hormones have been tested in this context, in particular somatostatin, bombesin, and serotonin.

CONCLUSIONS

Neuroendocrine differentiation in carcinoma of the prostate appears to be associated with poor prognosis, tumor progression, and the androgen-independent state, for which there is currently no successful therapy. Therefore, new therapeutic protocols and trials need to be developed to test drugs based on neuroendocrine hormones and/or their antagonists. An evaluation of this new therapeutic approach against prostatic carcinoma with neuroendocrine differentiation, including hormone-refractory cancer, is easily justified, since these tumors are unresponsive to current modes of therapy.

Cells in various benign and malignant conditions of the human prostate express different antigenic phenotypes

Prostatic epithelium basically consists of secretory-luminal, basal and endocrine-paracrine cells. Immunohistochemical procedures are frequently used for showing the cells reflecting different differentiations. In this study, 40 prostatic tissue specimens submitted to the Department of Pathology of Inönü University, Research Hospital, between 1991 and 1996 were examined. Half of the cases were diagnosed as cancer and the other half had various benign lesions. Of the cases 22.5% (n = 9) were needle biopsy material whereas the remainder, 47.5% (n = 19), were from prostatectomy and 30% (n = 12) were transurethral resection of the prostate (TURP) specimens. High molecular weight anti-cytokeratin antibodies (HMW anti-cytokeratin) stained basal cells both in all normal prostatic tissue and benign prostatic lesions, but in the majority of cancers (70%, n = 14) negative immunoreactivity was seen. Nevertheless, in some of the cancer cases (30%, n = 6) basal cell anti-cytokeratin staining was shown. Negative immunoreactivity with HMW anti-cytokeratin is important in distinguishing between malignant and benign lesions, whereas positive staining is not every time in favour of benign lesions. With the usage of prostate specific antigen (PSA) it was seen that all of the malignant and benign prostatic lesions stained positively. Basal cells in hyperplastic glands were not stained with this stain. Irregular, and in some areas, intense (PSA) immunoreactivity is present in precancerous and malignant lesions. Endocrine cells, which are represented with Chromogranin-A (Chr-A) immunoreactivity and reflecting neuroendocrine differentiation, are present in 75% (n = 15) of benign lesions and in 50% (n = 10) of cancer cases. It was thought that the lesser number of these cells in neoplastic lesions in comparison to the non-tumoral lesions is correlated with the disorder of mechanism that regulates the cell growth. Both in neoplastic and non-tumoral tissues the prostatic epithelial cells showed the three markers, namely HMW anti-cytokeratin, PSA, and Chr-A, which may reflect the multidirectional differentiation of these cells from a pluripotent origin.

Neuroendocrine cells in the normal, hyperplastic and neoplastic prostate

Neuroendocrine cells can be demonstrated in normal, hyperplastic and neoplastic prostatic tissues. The products secreted by these cells can be used as tissue and/or serum markers but may also have biological effects. Neuroendocrine cells in prostate cancer most probably do not contain the androgen receptor and are therefore primarily androgen independent. Some of the neuropeptides secreted by the neuroendocrine cells may act as growth factor by activation of membrane receptors in an autocrine-paracrine fashion or by ligand-independent activation of the androgen receptor in neighboring non-neuroendocrine cells. Evidence is accumulating from experiments with tumor models that neuropeptides indeed can influence the growth of prostatic tumor cells. Future research on neuroendocrine differentiation may answer some questions concerning the biological behavior of clinical prostatic tumors.

The prostatic endocrine-paracrine (neuroendocrine) regulatory system and neuroendocrine differentiation in prostatic carcinoma: a review and future directions in basic research

Endocrine-paracrine (neuroendocrine, amine precursor uptake and decarboxylation [APUD]) cells of the prostato-urethral region are serotonin and peptide containing regulatory cells, which are part of a dispersed neuroendocrine regulatory system also known as the APUD system. These cells most likely regulate growth and differentiation, as well as the secretory functions of the prostate. Prostatic carcinoma exhibits neuroendocrine differentiation in 3 forms: 1) small cell neuroendocrine carcinoma, 2) carcinoid-like tumors and 3) conventional prostatic adenocarcinoma with focal neuroendocrine differentiation. Small cell carcinoma and carcinoid-like tumors are rather rare (1 to 2% of all prostatic malignancies) and generally pursue an aggressive course. Focal neuroendocrine differentiation in adenocarcinoma is extensive in 10% of the cases and may be present in virtually all adenocarcinomas to a minor degree. There are conflicting studies on the prognostic significance of focal neuroendocrine differentiation in prostatic carcinoma, although several suggest a poor prognosis. The finding that serum neuroendocrine markers predict initial insensitivity to or the development of resistance to hormonal suppression therapy, coupled with the recent observation that androgen receptor is not expressed in neoplastic neuroendocrine cells suggests that neuroendocrine differentiation directly results in resistance to hormonal manipulation therapy. Neuroendocrine differentiation in prostatic carcinoma raises the possibility of innovative modes of treatment. Future directions of research should concentrate on the quantitative analysis of serotonin and various peptides in prostatic malignancy, since high levels of constitutive secretion may not be appreciated by immunocytochemistry, as well as analysis of tumors for receptors to neuroendocrine products, which are necessary for these products to have a functional role. Finally, specific subtypes of neoplastic cells with neuroendocrine differentiation based on serotonin and peptide profiles should be analyzed.

Calcitonin releases acid phosphatase from rat ventral prostate explants

Inclusion of salmon calcitonin in the culture medium of rat ventral prostate explants diminished l-tartarate-sensitive acid phosphatase activity in the tissues with a concomitant increment of the enzyme activity in the medium. The effect of the hormone was dose-dependent for a dose range of 10(-12)-10(-6) M. Acid phosphatase activity in prostate explants decreased from 38.6 +/- 3.5 to 20.5 +/- 2.8, whereas it increased from 0.60 +/- 0.15 to 2.80 +/- 0.40 nmol p-nitrophenol liberated/mg protein/30 min in the culture medium. Tissues exposed to 10(-6) M salmon calcitonin had higher acetylcholinesterase activity (8.8 +/- 0.7) than non-exposed ones (6.2 +/- 0.5 mumol substrate hydrolyzed/g tissue/min). These results suggest that locally produced calcitonin causes a release for prostatic acid phosphatase from prostate tissues possibly through its interaction with the cholinergic system.

CCK-containing paraneurons in human adenomatous prostate

The presence of CCK-containing neuroendocrine cells in human adenomatous prostates, and the colocalization of CCK together with serotonin in the same cell, have been demonstrated by means of an immunohistochemical technique and by a double labeling immunofluorescent staining. CCK-containing neuroendocrine cells had a focal distribution in the prostates and sometimes showed dendrite-like cytoplasmic processes. The major part of CCK (96.55%) colocalized with serotonin. CCK probably stimulates muscle contraction and endocrine/exocrine secretions in the urogenital tract.

Neuroendocrine differentiation in carcinoma of the prostate. Diagnostic, prognostic, and therapeutic implications

Endocrine-paracrine cells of the prostate (also known as APUD or neuroendocrine cells) constitute, in addition to the basal and exocrine secretory cells, a third population of highly specialized epithelial cells in the prostate gland. These endocrine-paracrine cells contain, and most likely secrete, serotonin and calcitonin, as well as variety of other peptides. Little is known of the functional role of these cells, but they probably subserve a paracrine or local regulatory role. They may also regulate via endocrine, lumencrine, or neurocrine mechanisms. These endocrine-paracrine cells probably play a significant role during prostatic growth and differentiation as well as regulating the secretory process of the mature gland. Neuroendocrine differentiation in prostatic carcinoma occurs in the form of the relatively rare small cell carcinoma and carcinoid or carcinoid-like tumor, but most commonly as focal neuroendocrine differentiation in a conventional prostatic adenocarcinoma that is a very frequent, if not ubiquitous phenomenon, and reflects tumor cell heterogeneity mimicking the normal differentiation process. The world's literature on neuroendocrine differentiation in prostatic carcinoma is reviewed. Neuroendocrine differentiation in all types of prostatic carcinoma appears to correlate with a poor prognosis. This correlation is probably multifactorial and may relate to a positive correlation with grade, a direct resistance to hormonal manipulation, and/or autocrine/paracrine growth factor activity due to the secretion of neuroendocrine products. Neuron-specific enolase and chromogranin, as well as other neuroendocrine products, may be useful as serum markers in patients with prostatic carcinoma with neuroendocrine differentiation. New therapeutic strategies need to be developed to treat these tumors. This includes the use of specialized protocols that have been effective against neuroendocrine carcinomas arising in other organ systems.

Immunocytochemistry of paraneurons in the female urethra of the horse, cattle, sheep, and pig

The aim of this study is to describe the presence of neuroendocrine (NE) cells (paraneurons), producing biogenic amines and/or peptidergic hormones, in the female urethra of cattle, sheep, pigs, and horses, by means of histochemical and double labeling immunofluorescent techniques. 5-Hydroxy-tryptamine-, chromogranin A-, cholecystokinin- and somatostatin-containing NE cells are present in the urethral epithelium of all the species studied, with the unique exception of the lack of somatostatin cells in the horse. Paraneurons containing 5-hydroxytryptamine colocalized with chromogranin A or cholecystokinin were also found in all subjects. Such active substances are hypothesized to play a role in the contraction of the urethral musculature, emission of urogenital fluids, and inhibition of endocrine and exocrine secretions.

Neuroendocrine differentiation in human prostatic carcinoma

Endocrine-paracrine (APUD, neuroendocrine) cells are located in the prostatic ductal and acinar epithelium. These cells are of the open and closed type and have dendritic processes. There is a wide range of secretory granule morphology presumably indicating a variety of different cell "types." Secretory immunoreactive peptides include serotonin, calcitonin (and related peptides), somatostatin, bombesin-like, thyroid-stimulating hormone-like (beta chain), and alpha-glycoprotein chain-like. These cells may function by endocrine, paracrine, neurocrine, and lumencrine mechanisms and play an important regulatory role both during growth and differentiation of the prostate as well as in the secretory process of the mature gland. Neuroendocrine differentiation in prostatic carcinoma is a frequent occurrence and manifests itself in several forms, including (1) small cell carcinoma, (2) carcinoid and carcinoid-like tumors, and (3) conventional adenocarcinoma with focal neuroendocrine differentiation. This latter pattern is the most common, and there is evidence that all or nearly all prostatic adenocarcinomas show at least some focal neuroendocrine differentiation. A review of the world's literature on this topic is included. Neuroendocrine differentiation generally portends a poorer prognosis but may also correlate directly with the grade. There is some evidence to suggest that neoplastic cells with neuroendocrine differentiation are resistant to hormonal therapy. Eutopic and ectopic hormone production may allow screening for prostatic carcinoma and/or monitoring for recurrence of prostatic carcinomas. Finally, the more basic implications of endocrine-paracrine cells and neuroendocrine differentiation are speculated on in reference to prostatic carcinogenesis and autocrine/paracrine tumor growth factor activity.

Alpha-fetoprotein-producing urachal adenocarcinoma

A 45-year-old Japanese male with a history of macroscopic hematuria for more than 6 months presented multiple metastatic lesions in the lungs. Cystoscopic examination demonstrated a large tumor mass protruding from the dome of the urinary bladder. Ultrasonography and CT highlighted a solid and cystic urachal tumor continuous from the vesical dome to the navel. Serum levels of alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) were elevated to 17,100 ng/ml and 17.7 ng/ml, respectively. He underwent palliative curettage of the vesical dome tumor twice, followed by chemotherapy with little effect. One year after admission, he died of progressive metastases to the lungs, left pleura, liver and brain. Final serum levels of AFP and CEA were 86,200 ng/ml and 60.9 ng/ml, respectively. The tumor was histologically classified as adenocarcinoma with a medullary growth pattern. Both papillotubular and solid (hepatoid) components were observed. The cancer cells were rich in glycogen and were immunoreactive diffusely for AFP and focally for CEA. CA15-3, CA19-9, epithelial membrane antigen and cytokeratin were also positive. In addition, argyrophilic cancer cells with immunoreactivities of neuron-specific enolase, chromagranin A and peptide YY were demonstrated. To our knowledge, this is the first reported case of AFP-producing adenocarcinoma of urachal origin.

Neurotensin is localized to paracrine cells in the urinary bladder of the turtle, Chrysemys picta

Urinary bladder from the painted turtle, Chrysemys picta, contains a substantial population of endocrine/paracrine cells scattered through the mucosal epithelium which immunostains using antisera directed toward mammalian neurotensin (NT). Radiommunoassay of 0.1 N HCl extracts of Chrysemys bladder indicated an immunoreactive NT (iNT) concentration of 161 +/- 39 pmol/g tissue (n = 9), an amount lower but comparable in magnitude to that found in mucosal scrapings of the intestine (926 +/- 125 pmol/g, n = 9). Bladder and intestinal iNT were indistinguishable during chromatography on Sephadex G-25 and HPLC on mu-Bondapak C18 where they eluted at the same position as avian NT. Similar results were obtained by immunocytochemistry and radioimmunoassay of urinary bladders from Pseudemys scripta scripta, P. scripta elegans, and P. floridana, three emydid species closely related to C. picta, but not from Sternotherus odoratus and Trionyx spinifer asper, representatives of the families Kinosternidae and Trionychidae, respectively, although positive results were obtained with intestinal preparations from these species. NT cells were not seen in urinary bladder from Rana pipiens, Bufo marinus, Necturus maculosus, or Anolis carolinensis. Thus, the presence of NT-containing cells in urinary bladder is not common among subavian vertebrates and may even be restricted to the Emydidae family of chelonians.

The endocrine-paracrine cells of von Brunn's nests and glandular metaplasia in the supramontanal prostatic urethra

Endocrine-paracrine (EP) cells are normal cellular constituents of the human genitourinary tract. We examined the distribution and immunostaining profile of EP cells in von Brunn's nests and glandular metaplasia in the supramontanal (proximal) prostatic urethra of adult males and in prostatic ducts of the male fetal urethra. In 15/17 transurethral prostatic resection specimens there were argyrophilic cells and/or serotonin and neuronspecific enolase containing cells in von Brunn's nests/glandular metaplasia and in the supramontanal prostatic urethra. All seven fetal specimens examined contained EP cells and five had focal calcitonin immunoreactivity in prostatic ducts and ductal buds. One adult resection specimen had focal staining for human chorionic gonadotrophin and no case showed staining for somatostatin. These results further support the contention that von Brunn's nests and glandular metaplasia are probably normal urothelial variants in the adult supramontanal prostatic urethra.

Endocrine cells in human Bartholin's glands. An immunohistochemical and ultrastructural analysis

Endocrine cells were investigated in human Bartholin's glands by use of histochemical, immunohistochemical and ultrastructural methods. Endocrine cells represent normal constituents of these glands, being mainly distributed throughout the transitional epithelium of the major excretory duct; however, single elements are dispersed among the acinar lobules. Serotonin-, calcitonin-, katacalcin-, bombesin- and alpha-hCG-immunoreactive cells were recognized, with serotonin-immunoreactive cells predominating. Co-expression of calcitonin, katacalcin or alpha-hCG with serotonin was observed in single endocrine cells. At the ultrastructural level, these cells are richly granulated and show typical neuroendocrine features. Bartholin's glands display an endocrine profile quite similar to that of other cloacal-derived tissues.

Endocrine cells in the excurrent duct system of the testis. An immunohistochemical analysis

A systematic search for endocrine cells in the excurrent duct system of the testis was carried out by means of histochemical and immunohistochemical techniques. A panel of antibodies against amine and polypeptide hormones was used. 80 specimens comprising representative areas of rete testis, ductuli efferentes, ductus epididymis and 30 examples of ductus deferens were investigated. Cells immunoreactive for serotonin were detected in four out of 110 specimens. They were invariably in normal-appearing ductuli efferentes. A salient feature was their rarity and focal distribution. We failed to detect any endocrine cells in other segments of the excurrent duct system and notably not among epididymal epithelium. It seems of interest that serotonin cells are specifically distributed throughout remnants of excretory mesonephric tubules in both males and females.

Immunoextracted calcitonin in human gastric secretion

Immunoreactive calcitonin (iCT) has been demonstrated in human gastric juice after immunoextraction with immobilized antibodies and subsequent radioimmunoassay. The basal levels were 4.5 +/- 3.1 (mean +/- SD) pg-Eq/ml gastric juice; range 1.2-9.1 pg-Eq/ml; n = 7, and after stimulatory gastric secretion test with pentagastrin 0.3 +/- 0.2 pg-Eq/ml; range 0.1-0.7 pg-Eq/ml; n = 7 (p less than 0.01). The main fraction of iCT from gastric juice eluted in the same region as synthetic human calcitonin (hCT) on Sephadex G-75 gel chromatography. Reverse phase chromatography in a fast protein liquid chromatography (FPLC) system revealed a slightly less hydrophobic character of the iCT from gastric juice compared to synthetic monomeric hCT. The results were further confirmed by using an additional antiserum. In plasma, the calcitonin (CT) levels were after immunoextraction at the basal state 6.6 +/- 1.7 pg-Eq/ml (mean +/- SD); range 5.1-10.1 pg-Eq/ml; n = 7 and after pentagastrin stimulation 9.4 +/- 5.4 pg-Eq/ml; range 6.3-18.5 pg-Eq/ml; n = 7.

Endocrine differentiation in inflamed urinary bladder epithelium with metaplastic changes

Several types of metaplasia can occur in human bladder epithelium under certain pathological conditions. We investigated 65 cases of cystitis, associated with different types of metaplasia, for the presence of endocrine cells, using histochemical and immunocytochemical methods. Tissues were obtained at cystoscopy and were routinely fixed in 10% buffered formalin. Endocrine cells were demonstrated, between the epithelial cells, in 40 out of 50 cases of cystitis glandularis or cystica. These cells were positive by the Grimelius' silver impregnation technique and were immunoreactive for protein gene product (PGP 9.5), a new general neuroendocrine marker, chromogranin and serotonin. No endocrine cells were detected in any of the specimens of normal epithelium nor those showing squamous metaplasia. Eighteen of these cases showed prominent nerve bundles in the subepithelial tissue, as revealed by PGP immunoreactivity.

Endocrine cells in ectocervical epithelium. An immunohistochemical and ultrastructural analysis

A systematic study of endocrine cells in the ectocervix was carried out using histochemical, immunohistochemical and ultrastructural techniques. Serotonin and calcitonin immunoreactive cells were demonstrated in this site. Serotonin and calcitonin immunoreactivities were coexpressed in the same endocrine cell. These distinctive cells were encountered in two main morphological varieties of ectocervical epithelium. Normal-appearing stratified squamous epithelium contained only very rare serotonin and calcitonin cells. In contrast, endocrine cells were fairly abundant in a specific epithelium termed "transitional-like". This type of epithelium was not only confined to the transformation zone but could also extend onto the portio as far as the vaginal cut margin. In some cases, transitional-like epithelium bore morphological resemblance to urothelium. In other cases, it could be regarded as basal cell hyperplasia or immature squamous metaplasia. Of interest, serotonin and calcitonin cells have been well-documented as normal inhabitants of some other non-squamous epithelia, such as urothelium or pseudostratified columnar epithelium. Therefore, it is suggested that certain ectocervical epithelia show some similarities to urothelium, in respect of their morphological appearance and endocrine profile. Further investigations using more objective and specific markers of urothelial cells are needed to assess the exact degree of homology connecting all these types of epithelium.

Determination of serotonin and 5-hydroxyindoleacetic acid in guinea pig and human prostate using HPLC

The finding of significant numbers of endocrine-paracrine (EP) cells in the prostate glands of guinea pigs and man suggests that these cells may be important in the regulation or modulation of prostatic function. Serotonin is a biogenic amine common to most prostatic EP cells. In order to extend current knowledge relating to these cells, an assay was developed using high-performance liquid chromatography to quantitate serotonin and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in guinea pig and human prostatic tissue extracts. Levels of serotonin and 5-HIAA in the guinea pig whole-gland preparation were 105.4 +/- 70.6 ng/g and 48.4 +/- 95.7 ng/g, respectively. Normal human prostatic tissue contained 1423.9 +/- 750.8 ng/g serotonin and 66.7 +/- 92.8 ng/g 5-HIAA. Recoveries ranged between 60 and 100%. The detection limits were 24 pg/injection for serotonin and 12 pg/injection for 5-HIAA. This assay provides an expeditious, specific and highly sensitive method for the simultaneous determination of monoamines in guinea pig and human prostatic tissue.