Pro-dynorphin is endogenous to the anterior pituitary and is co-localized with LH and FSH in the gonadotrophs

Cell-specific effects of variants of the 68-base pair tandem repeat on prodynorphin gene promoter activity

A polymorphic 68-bp tandem repeat has been identified within the promoter of the human prodynorphin (PDYN) gene. We found that this 68-bp repeat in the PDYN promoter occurs naturally up to five times. We studied the effect of the number of 68-bp repeats, and of a SNP (rs61761346) found within the repeat on PDYN gene promoter activity. Thirteen promoter forms, different naturally occurring combinations of repeats and the internal SNP, were cloned upstream of the luciferase reporter gene, transfected into human SK-N-SH, H69, or HEK293 cells. Cells were then stimulated with TPA or caffeine. We found cell-specific effects of the number of 68-bp repeats on the transcriptional activity of the PDYN promoter. In SK-N-SH and H69 cells, three or four repeats led to lower expression of luciferase than did one or two repeats. The opposite effect was found in HEK293 cells. The SNP also had an effect on PDYN gene expression in both SK-N-SH and H69 cells; promoter forms with the A allele had significantly higher expression than promoter forms with the G allele. These results further our understanding of the complex transcriptional regulation of the PDYN gene promoter.

A synthetic peptide derived from mouse pituitary calcitonin cDNA sequence exhibits potent inhibition of prolactin secretion and prolactin mRNA abundance in primary mouse pituitary cells

We have shown that gonadotrophs synthesize and secrete immunoreactive calcitonin (CT)-like peptide, and CT is a potent inhibitor of prolactin (PRL) secretion and gene transcription. CT cDNA cloned from LssT2 cells (pit-CT cDNA) exhibits 99% homology with mouse CT cDNA sequence, but exhibits four mismatches in the coding region of CT peptide (347-485 bp) with consequent changes in the amino acids at positions 5 and 17 of mouse CT. We have synthesized a putative 23 amino acid pit-CT peptide based on pit-CT cDNA sequence, and tested its effect on PRL secretion and mRNA abundance in primary mouse pituitary cells. The results suggest that synthetic pit-CT attenuates PRL mRNA abundance and inhibits PRL release from mouse anterior pituitary cells. Moreover, pit-CT is remarkably more potent than salmon (S)CT in attenuating PRL mRNA abundance. These results raise a possibility that this endogenous pituitary peptide may potentially serve as a therapeutic molecule for the treatment of prolactinomas.

Targeted overexpression of calcitonin in gonadotrophs of transgenic mice leads to chronic hypoprolactinemia

It was previously shown that calcitonin-like pituitary peptide (pit-CT) is synthesized and secreted by gonadotrophs, and pit-CT inhibits PRL gene transcription and lactotroph cell proliferation. Present studies examined long-term consequences of pit-CT overexpression on the functioning of mouse anterior pituitary (AP) gland. Targeted overexpression of pit-CT in gonadotrophs of mouse pituitaries was achieved by generating mice overexpressing bovine luteinizing hormone (LH)-alpha subunit promoter-pit-CT cDNA transgene. Transgenic (pit-CT+) mice displayed chronic but selective overexpression of pit-CT in gonadotrophs. The mice also displayed a dramatic decline in PRL gene expression as assessed by PRL mRNA abundance, PRL immunohistochemistry (IHC) and serum PRL levels. LH secretion in pit-CT+ mice was also reduced, without any change in FSH secretion. Reproductive abnormalities such as prolonged estrous cycles, reduced pregnancy rate, delivery of smaller litters, increased neonatal mortality and deficient lactation were also observed. Administration of PRL during early pregnancy significantly increased the pregnancy rate and neonatal survival of newborns. These results demonstrate that overexpression of pit-CT leads to chronic hypoprolactinemia and reproductive dysfunction in female mice, and reinforces the possibility that gonadotroph-derived pit-CT is an important paracrine regulator of lactotroph function.

Interaction between anterior pituitary prodynorphin and the secretion of luteinizing hormone (LH)

The purpose of present research was to investigate the possible involvement of prodynorphin (proDYN)-derived peptides acting locally within the anterior pituitary (AP) on the effects of estradiol-17 beta (E2) and gonadotropin-releasing hormone (GnRH) on the release of luteinizing hormone (LH). Exposure of bovine AP cells in primary suspension cultures to E2 increased (P < 0.05) the spontaneous release of proDYN-derived peptides and also augmented (P < 0.05) the GnRH-induced release of LH. Both of these E2-induced responses required either high E2 dosages or prolonged exposure to produce significant changes, but there were a few cases in which the association between E2-induced changes in both parameters was absent. Therefore, it seems unlikely that proDYN-derived AP peptides mediate the effects of E2 on GnRH-induced LH release. Using another approach, cultured cells were exposed for 48 h to an antisense oligodeoxynucleotide (oligo) targeted against the translation initiation site of bovine proDYN. Compared with the two control treatments (scrambled oligo sequence or no oligo treatment), the antisense treatment decreased (P < 0.05) the quantity of LH released in response to challenge of the cells with 5 nM GnRH. There were no concurrent changes in cellular contents of proDYN-derived peptides or mRNA for LH-beta, but the antisense treatment tended to decrease (P < 0.10) the relative abundance of proDYN mRNA. In summary, proDYN-derived peptides probably do not mediate direct intrapituitary effects of E2 on LH, but the antisense treatment interfered in an unknown way with GnRH-induced release of LH from cultured AP cells.

Prodynorphin processing by proprotein convertase 2. Cleavage at single basic residues and enhanced processing in the presence of carboxypeptidase activity

Endoproteolytic processing of the 26-kDa protein precursor prodynorphin (proDyn) at paired and single basic residues is most likely carried out by the proprotein convertases (PCs); however, the role of PCs at single basic residues is unclear. In previous studies we showed that limited proDyn processing by PC1/PC3 at both paired and single basic residues resulted in the formation of 8- and 10-kDa intermediates. Because PC2 is colocalized with proDyn, we examined the potential role of this convertase in cleaving proDyn. PC2 cleaved proDyn to produce dynorphin (Dyn) A 1-17, Dyn B 1-13, and alpha-neo-endorphin, without a previous requirement for PC1/PC3. PC2 also cleaved at single basic residues, resulting in the formation of the C-peptide and Dyn A 1-8. Only PC2, but not furin or PC1/PC3, could cleave the Arg-Pro bond to yield Dyn 1-8. Structure-activity studies with Dyn A 1-17 showed that a P4 Arg residue is important for single basic cleavage by PC2 and that the P1' Pro residue impedes processing. Conversion of Dyn A 1-17 or Dyn B 1-13 into leucine-enkephalin (Leu-Enk) by PC2 was never observed; however, Dyn AB 1-32 cleavage yielded small amounts of Leu-Enk, suggesting that Leu-Enk can be generated from the proDyn precursor only through a specific pathway. Finally, PC2 cleavages at single and paired basic residues were enhanced when carried out in the presence of carboxypeptidase (CP) E. Enhancement was blocked by GEMSA, a specific inhibitor of CPE activity, and could be duplicated by other carboxypeptidases, including CPD, CPB, or CPM. Our data suggest that carboxypeptidase activity enhances PC2 processing by the elimination of product inhibition caused by basic residue-extended peptides.

Dynorphin and epilepsy

Studies on dynorphin involvement in epilepsy are summarised in this review. Electrophysiological, biochemical and pharmacological data support the hypothesis that dynorphin is implicated in specific types of seizures. There is clear evidence that this is true for complex partial (limbic) seizures, i.e. those characteristic of temporal lobe epilepsy, because; (1) dynorphin is highly expressed in various parts of the limbic system, and particularly in the granule cells of the hippocampus; (2) dynorphin appears to be released in the hippocampus (and in other brain areas) during complex partial seizures; (3) released dynorphin inhibits excitatory neurotransmission at multiple synapses in the hippocampus via activation of kappa opioid receptors; (4) kappa opioid receptor agonists are highly effective against limbic seizures. Data on generalised tonic-clonic seizures are less straightforward. Dynorphin release appears to occur after ECS seizures and kappa agonists exert a clear anticonvulsant effect in this model. However, more uncertain biochemical data and lack of efficacy of kappa agonists in other generalised tonic-clonic seizure models argue that the involvement of dynorphin in this seizure type may not be paramount. Finally, an involvement of dynorphin in generalised absence seizures appears unlikely on the basis of available data. This may not be surprising, given the presumed origin of absence seizures in alterations of the thalamo-cortical circuit and the low representation of dynorphin in the thalamus. In conclusion, it may be suggested that dynorphin plays a role as an endogenous anticonvulsant in complex partial seizures and in some cases of tonic-clonic seizures, but most likely not in generalised absence. This pattern of effects may coincide with the antiseizure spectrum of selective kappa agonists.

Release of alpha-neoendorphin from the anterior pituitary gland of conscious rats

alpha-Neoendorphin (alpha-NEO) is a proenkephalin B-derived opioid peptide and kappa type opioid receptor agonist. In the present study, we used a combination of microdialysis and a highly sensitive radioimmunoassay to measure the extracellular levels of immunoreactive (ir)-alpha-NEO from the anterior pituitary gland of conscious free-moving rats. When rats were given water ad libitum under a 12:12 h light-dark cycle with lighting from 06.00 to 18.00 h, ir-alpha-NEO showed circadian rhythmicity that peaked at 00.00-03.00 h and reached a minimum at 12.00-15.00 h. Furthermore, we investigated whether naloxone (10(-6) to 10(-8) M) affected ir-alpha-NEO level. The alpha-NEO release induced by naloxone was optimum at 10(-7) M, and 10(-6) M naloxone seemed to induce alpha-NEO release to a lesser degree. These results suggested that alpha-NEO release by naloxone might be mediated via anterior pituitary cell auto-receptor (kappa type) inhibition.

Processing of prodynorphin by the prohormone convertase PC1 results in high molecular weight intermediate forms. Cleavage at a single arginine residue

Processing of rat prodynorphin (proDyn) by the mouse prohormone convertase PC1 was investigated. Recombinant vaccinia virus vectors were used to coexpress proDyn and PC1 in rat PC12 pheochromocytoma and mouse AtT-20 corticotroph cells. In vitro experiments were also conducted by co-incubating purified proDyn and PC1. The results demonstrate that PC1 cleaves proDyn at pairs of basic residues to yield 10 and 16 kDa high molecular weight (HMW) intermediates. Additionally, PC1 cleaves proDyn at a single arginine residue to yield an 8 kDa product and the C-peptide. This demonstrates that PC1 cleaves proDyn at single and pairs of basic residues.

Sexual dimorphism in the distribution of alpha-neoendorphin-like immunoreactivity in the anterior pituitary of the rat

The localization of the opioid peptide alpha-neoendorphin (alpha-Neo-E) was studied in the anterior pituitary of normal and castrated male and normal female rats. Immunoreactive (ir) cells were noted in both sexes. These alpha-Neo-E-ir cells were further characterized using double immunostaining with an elution-restaining procedure. It was seen that in males, alpha-Neo-E-ir cells corresponded mainly to luteinizing hormone/follicle-stimulating hormone cells and a few thyroid-stimulating hormone (TSH) cells, whereas in females, virtually all alpha-Neo-E-ir cells corresponded to TSH cells. Castration of male rats caused, within 3 to 5 days a dramatic decrease in the number of alpha-Neo-E-ir gonadotrophs, whereas the number of alpha-Neo-E-ir TSH cells tended to increase. Two weeks after castration, however, most alpha-Neo-E-ir cells were also follicle-stimulating hormone-ir. This study demonstrates that in the anterior lobe of the rat, alpha-Neo-E-ir is located within gonadotrophs and/or thyrotrophs, depending on the sex. In addition, results obtained following castration suggest that the expression of this peptide in the anterior pituitary depends upon the steroid environment, possibly indicating that alpha-Neo-E is implicated in the regulation of the pituitary-gonadal axis.

Immunoreactive dynorphin A-like material in extracted human hypothalamic-hypophysial plasma

Immunoreactive dynorphin A-like material (ir-dyn A) in human plasma was measured by a validated radioimmunoassay. In peripheral plasma extracts mean concentrations between 20 and 40 fmol/ml were determined in volunteers and in patients with pituitary adenomas. In this latter group superimposable levels were detected three days before and during transsphenoidal microsurgery. Interestingly, ir-dyn A levels evaluated in extracts of hypothalamic-hypophysial plasma obtained during surgery, just after tumor removal, were 4-5 times higher than in peripheral plasma. Reverse-phase high performance liquid chromatography (rp-HPLC) of extracts of peripheral plasma samples revealed two immunoreactive peaks. The major form had the same retention time of dyn A-(1-32); whereas a second, more lipophilic, peak eluted later and was not further characterized. In contrast, rp-HPLC analysis of extracts of plasma collected from the suprapituitary region displayed only one peak eluting in the position of synthetic dyn A-(1-17). The presence of dyn-related peptides in hypothalamic-hypophysial plasma supports the hypothesis that they may play a part in the regulation of hypothalamic and/or pituitary functions in humans.

Differential regulation of anterior pituitary prodynorphin and gonadotropin-subunit gene expression by steroid hormones

Prodynorphin is expressed by neurons of the hypothalamus and gonadotrophs of the anterior pituitary gland (AP) and plays a role in the negative feedback regulation of the reproductive neuroendocrine axis. The present study examined whether gonadal steroid hormones are capable of modulating pituitary prodynorphin expression in immature, female rats. Steroids were administered via subcutaneous Silastic implants and rats were killed at 29 days of age. Northern blot analysis was used to measure AP prodynorphin, luteinizing hormone-beta (LH beta), follicle-stimulating hormone-beta (FSH beta), and common alpha-subunit mRNA levels (normalized to 18S ribosomal RNA). Treatment groups (n = 5-6) consisted of control (CNT; empty implants), estradiol (E2; 4 days), E2 + progesterone (E2 + P4; 8 days and 4 days, respectively), and dihydrotestosterone (DHT; 4 days). Pituitary prodynorphin mRNA was significantly suppressed in only the DHT-treated animals (26 +/- 10% of CNT, p < 0.01). LH beta mRNA was suppressed by all steroid treatments (p < 0.01), FSH beta was lower in only the E2 group, and alpha-subunit was reduced in both the E2 + P4 and DHT groups (p < 0.01). Serum LH was suppressed by all steroid treatments but FSH was reduced in only the E2 and E2 + P4 groups (p < 0.01). Treatment of prepubescent rats with continuous high levels of gonadal steroids is known to severely reduce endogenous hypothalamic gonadotropin releasing hormone (GnRH) release and this is supported by our observation of reduced gonadotropin-subunit gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructure of spontaneous and transplanted pituitary tumors in laboratory animals

The present review examines ultrastructural studies of pituitary tumors in laboratory animals. Such studies have been facilitated by the development of newer techniques such as immunocytochemistry and in situ hybridization. Using these methods it has been possible to correlate morphological features with function by characterizing specific pituitary hormones in secretory granules and analyzing the messenger ribonucleic acids produced by specific cell types. Analyses of spontaneous and experimentally induced tumors have provided a great deal of insight into the function and ultrastructure of these neoplasms. The description of tumor cells producing more than one hormone has been facilitated by immunocytochemical analyses. Studies of transgenic models of pituitary hyperplasia and tumor development are expanding our knowledge about the ultrastructure and about other aspects of pituitary tumors in a more controlled experimental setting. The production of various hormones by the same pituitary tumors and even the same tumor cells indicates that complex regulatory mechanisms must be analyzed by a combination of ultrastructural and other techniques to learn more about growth and hormone secretion in pituitary neoplasms.

Colocalized peptides in gonadotrophs: LeuEnkephalin and ACTH interact differently on GnRH induced LH and FSH release

Two peptides that have been previously colocalized in the gonadotrops (LeuEnkephalin with LH and ACTH with FSH) can stimulate the release of gonadotropins in primary culture of anterior pituitary cells. In presence of both substances, and in contrast to LHRH induced secretion, the augmentation of LH release is never dose dependent. It is always significantly higher than controls, for high (10(-6) M) or low concentrations (10(-12) M). Prolactin release is only modified in presence of Leu-Enkephalin. Met-Enkephalin does not increase the liberation of LH, FSH, or Prolactin in vitro. Furthermore, while Leu-Enkephalin can enhance the stimulating effect of LHRH, ACTH has a negative interaction with LHRH, when these two peptides are added together in incubation medium. These results demonstrate that Leu-Enkephalin and ACTH can in vitro modulate the release of gonadotrophins at the pituitary level suggesting a physiological role for such colocalization.

Gonadal steroids and anterior lobe dynorphin in the male rat

Immunoreactive (ir)-dynorphin levels were measured, and the species characterized by high performance liquid chromatography (HPLC), in the pituitary and hypothalamus of intact and castrate male rats. On HPLC, ir-dynorphin co-eluted with authentic dynorphin A 1-8, dynorphin A 1-17 and dynorphin 1-32 in the hypothalamus and intermediate lobe; in two different reversed phase (RP)-HPLC systems, anterior lobe ir-dynorphin co-eluted uniquely with dynorphin 32 (4K dynorphin). Anterior lobe levels of total ir-dynorphin were significantly lowered 7 days after castration, while HPLC profiles in all tissues remained unchanged. The change in anterior pituitary ir-dynorphin levels was reversed in a dose-related manner by dihydrotestosterone (15-500 micrograms/100 g b. wt/day); estradiol benzoate (3 micrograms/100 g/day) was without effect. The changes on castration and androgen administration suggest that gonadal steroids play a role in the regulation of dynorphin, as well as gonadotrophins and prolactin, within the anterior pituitary gland.

Immunocytochemistry of four mixed pituitary adenomas and intrasellar gangliocytomas associated with different clinical syndromes: acromegaly, amenorrhea-galactorrhea, Cushing's disease and isolated tumoral syndrome

Four tumors consisting of pituitary adenomatous cells (AD) intricated with ganglion cells (GC) were studied. Each case was associated with a different clinical syndrome: acromegaly, amenorrhea-galactorrhea, Cushing's disease and isolated tumoral syndrome with no hormonal hypersecretion. (a) In the case with acromegaly, immunoreactive growth hormone (IR-GH) was present in 80% of AD. IR-vasoactive intestinal peptide (VIP) was found in 5%-10% of AD and in few GC. Rare GC and processes showed IR-GH-releasing hormone (GRH), -somatostatin (SRIH), -gonadotropin-releasing hormone and -adrenocorticotropin-releasing hormone. (b) In the case with amenorrhea-galactorrhea, IR-prolactin (PRL) was seen in 90% of AD. IR-PRL and -VIP were present in rare GC. (c) In the case with Cushing's disease, 60% of AD and very few GC contained IR-adrenocorticotropin (ACTH) and beta-lipotropin. Rare GC processes contained IR-SRIH. (d) In the case without pituitary hormone hypersecretion, PRL was localized in rare AD and GC. Pituitary hormone and neuropeptides were never colocalized in the same cells. No case displayed IR-neurophysins or -thyroliberin. Pituitary hormones were localized by ultrastructural immunogold labeling. These findings show that: (i) in three cases, pituitary hormones (PRL and ACTH), and, in one case, VIP could be localized in both adenomatous and ganglion cells; (ii) the pituitary hormone-containing cells in the tumors could be related to the hypersecretory syndromes; (iii) intratumoral IR-VIP and -GRH might be involved in GH and PRL hypersecretion in the cases with acromegaly and amenorrhea-galactorrhea.

Role of the ventromedial hypothalamus in the regulation of adenohypophyseal immunoreactive dynorphin in the rat

In this study, we have examined the role of the dorsomedial (DMH), ventromedial (VMH) and arcuate (ARH) nuclei of the hypothalamus in the control of hypothalamic and pituitary immunoreactive (ir) dynorphin (Dyn) A and ir-Dyn B in the rat, by evaluating the effect of discrete, bilateral radiofrequency lesions in these structures. Lesions limited to the VMH reduced the content of ir-Dyn in the anterior pituitary but not in the neurointermediate lobe or in the hypothalamus. Gel chromatographic analysis of anterior pituitary extracts confirmed that ir-Dyn is mainly associated with high molecular weight forms containing Dyn A and Dyn B in their sequence. Anterior pituitary extracts of VMH-lesioned rats displayed a clearly lower proportion of these forms. Destruction of the DMH affected only the hypothalamic content of ir-Dyn; ablation of the ARH did not cause any significant change. Our results suggest that ablation of the VMH may disrupt critical neuronal connections to the median eminence originating in this nucleus or crossing it and participating in control of the adenohypophyseal pool of ir-Dyn.

In situ hybridization analysis of osmotic stimulus-induced changes in ribosomal RNA in rat supraoptic nucleus

A quantitative in situ hybridization analysis was used to investigate changes in levels of ribosomal RNA (rRNA) in neurons of the supraoptic nucleus (SON) of rats stimulated osmotically by giving 2% NaCl as drinking solution for 0 (control rats), 1, 4, and 14 days. The quantitation was autoradiographically accomplished by in situ hybridization with a nick-translated tritiated ribosomal DNA probe and with the use of computer-based image analysis system. The mean number of grains per neuron in the ventral SON was significantly increased: 1.8-fold for 1 day, 2.9-fold for 4 days, and 1.7-fold for 14 days of salt loading, whereas the mean number of grains per neuron in the dorsal SON was increased 1.3-fold for 1 day, 2.5-fold for 4 days, and 1.7-fold for 14 days. Kolmogorov-Smirnov analysis of frequency histograms of grains per neuron indicated that the amount of rRNA in neurons in the ventral and dorsal SON was significantly increased by osmotic stimulation. These increases were accompanied by increases in cell size. The subcellular location of hybridizable rRNA in magnocellular neurons was altered by osmotic stimulation. Following 1-14 days of salt-drinking, rRNAs appeared to be more unevenly distributed throughout the cytoplasm. These findings are consistent with the notion that hyperosmotic stimulation has a substantial effect on the expression of rRNA genes in neurons of both the ventral and dorsal SON.

Fine structural cytology of the adenohypophysis in rat and man

The present review deals with the use of electron microscopy in the identification of pituitary cell types as well as the assessment of their functional state, in rat and man. Application of immunoelectron microscopy, especially immunogold techniques, utilizing multiple labeling in establishing differentiation and hormone content of cell types, is emphasized. Recent evidence of plurihormonality in various pituitary cell types indicates that the once axiomatic one cell-one hormone theory is untenable and that the present perception of pituitary cell types and their function requires modification. Detection of hormonal and nonhormonal substances in pituitary cell types, not associated with their known endocrine function, suggests that hypophysial cells may have yet unknown roles, possibly in the realm of paracrine and autocrine regulation.

Subcellular distribution of dynorphin-like immunoreactivity in rat adenohypophysis in comparison with luteinizing hormone and follicle-stimulating hormone

Dynorphin and other proenkephalin B-derived peptides exist in the rat adenohypophysis in high concentrations and may have important roles in endocrine function. At the cellular level, dynorphin peptides are colocalized with the gonadotropins in at least a subpopulation of gonadotrophs. In this study dynorphin-containing particles were compared with secretory granules containing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by means of differential centrifugation and sucrose density gradient centrifugation. When anterior pituitary homogenate of male rats was subjected to differential centrifugation, about 70% of both dynorphin- and LH-containing particles sedimented at 30,000 x g. LH granules and dynorphin-containing particles comigrated in continuous sucrose density gradients both under nonequilibrium conditions as well as when equilibrium was attained. FSH storage granules were found to sediment in slightly denser fractions, with substantial overlap. Hence, dynorphin-containing particles and gonadotropin-containing granules exhibit similar characteristics. These hormones may, therefore, be colocalized also at the subcellular level or stored in separate but similar vesicles.

Alterations in regional concentrations of endogenous opioids following traumatic brain injury in the cat

Delayed injury following trauma to the central nervous system (CNS) may be due to the release or activation of endogenous factors. Endogenous opioid peptides have been proposed as one such class of injury factors, based on pharmacological studies demonstrating a therapeutic effect of naloxone and other opiate receptor antagonists following CNS injury. However, changes in brain opioid concentrations following injury have not been evaluated. In the present study, we measured regional alterations in dynorphin (ir-Dyn), leucine-enkephalin (ir-Enk) and beta-endorphin immunoreactivity (ir-End) following low- (1.0-2.0 atmospheres (atm)) or high- (3.0-4.0 atm) level fluid-percussion brain injury in the cat. A significant decrease in ir-End was observed in the hypothalamus at 2 h following high- but not low-level injury. No changes were observed in tissue ir-Enk following either level of injury. Severe brain trauma but not low-level injury caused a significant increase in ir-Dyn in the striatum, frontal cortex, parietal cortex, pons and medulla. In the anterior pituitary, a significant increase in ir-End and a significant decrease in ir-Dyn was observed at 2 h following both levels of injury. Pathological damage to brain tissue after injury was most pronounced in those regions showing significant increases in ir-Dyn but not other opioids. In the medulla, the increase in ir-Dyn but not ir-End or ir-Enk was also significantly correlated with a fall in systemic mean arterial pressure (MAP) at 2 h following high- but not low-level injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatographic characterization of dynorphin and [Leu5]enkephalin immunoreactivity in guinea pig and rat testis

Tissues of the reproductive tract have been shown to contain mRNAs coding for pro-opiomelanocortin (POMC), pro-enkephalin and pro-dynorphin. However, the amounts of immunoreactive opioid peptides in these tissues are low, and in the case of the enkephalins and dynorphin, the molecular species responsible for the immunoreactivities have not been characterized. The chromatographic properties of dynorphin and enkephalin immunoreactivities in extracts of guinea pig and rat testis have therefore been determined. Dynorphin A and dynorphin B immunoreactivity was heterogeneous, with a significant amount attributable to high-molecular-weight forms. About 20% of the dynorphin A immunoreactivity, and about 40% of the dynorphin B immunoreactivity, in guinea pig testis extracts behaved as authentic dynorphin A or B, respectively during fractionation by ion exchange, gel filtration and high-performance liquid chromatography. Both high- and low-molecular-weight forms of [Leu5]enkephalin immunoreactivity were also present, with roughly 50-70% of the immunoreactivity attributable to low-molecular-weight forms. In extracts of guinea pig testis only a small part of this immunoreactivity eluted as authentic [Leu5]enkephalin during high-performance liquid chromatography. In rat testis most of the low-molecular-weight [Leu5]enkephalin immunoreactivity behaved as the authentic peptide. These results confirm that opioid peptides are produced in guinea pig and rat testis, and demonstrate that immunoreactive forms of the peptides similar to those found in brain and pituitary are present in the tissue.

Persistence of immunoreactive TRH and GnRH in long-term primary anterior pituitary cultures

Intact anterior pituitary tissue and primary anterior pituitary cultures were stained with 1:30,000 anti-TRH and 1:10,000 anti-GnRH using the peroxidase antiperoxidase immunocytochemical technique. Stains applied to serial ultrathin sections of intact pituitaries showed that TRH immunoreactivity could be localized in secretory granules of thyrotropes, gonadotropes and corticotropes whereas GnRH immunoreactivity was found only in gonadotropes and corticotropes. Long-term primary pituitary cultures were studied to remove the anterior pituitary cells from hypothalamic influences. In these cell populations both TRH and GnRH immunoreactivity persisted. In addition, quantification of the stained cells at the light microscopic level demonstrated that the volume fraction of TRH and GnRH immunoreactive cells remained constant up to 3 weeks of culture. Studies of serial ultrathin sections through cells from these cultures showed TRH or GnRH localized in secretory granules of cells that contained LH and ACTH, but not TSH. Both liquid and solid phase immunoabsorption specificity controls were used to validate the immunocytochemical stains. These studies suggest that the pituitary TRH and GnRH immunoreactivities may not be completely of hypothalamic origin, but may also be endogenous to a subpopulation of unique multihormonal pituitary cells.

Immunoreactive dynorphin-A in bovine anterior pituitary and its in vitro release

The anterior lobe (AL) of the bovine pituitary contained and released, during in vitro culture, a form of immunoreactive dynorphin-A (ir-DYN-A) larger than that occurring in neural tissue. Bovine AL tissue from intact females contained less ir-DYN-A than did AL tissue from castrated males. Enzymatically dispersed AL cells contained and released ir-DYN-A in vitro. Preincubation of dispersed AL cells for 18 hr, rather than 1.5 hr, increased the content and release of ir-DYN-A as well as LH. Addition of gonadotropin-releasing hormone (GnRH) to tissue slices or dispersed cells stimulated release of LH, but in contrast to published observations from rat AL, GnRH had no effect on release of ir-DYN-A. Addition of estradiol-17 beta, with or without progesterone, increased release of ir-DYN-A but not LH during 2-hr cultures. In summary, bovine AL contains and releases in vitro a large molecular weight form of ir-DYN-A. Although this ir-DYN-A was not coreleased with LH, a reproductive role was suggested by in vivo and in vitro effects of gonadal hormones on ir-DYN-A in the bovine anterior pituitary.

Immunoreactive dynorphin-A in ovine anterior pituitary and effects of estradiol-17 beta administration

Anterior lobe (AL) tissue of the ovine pituitary gland contained a form of immunoreactive dynorphin-A (ir-DYN-A) larger than that found in pituitary neurointermediate lobe. Administration of estradiol-17 beta or estradiol-17 beta plus progesterone to ovariectomized sheep decreased AL tissue concentrations of ir-DYN-A but did not affect any LH parameter. Enzymatically dispersed AL cells also contained ir-DYN-A, but specific release during in vitro incubation was too low to be detected even when cells were exposed to gonadotropin-releasing hormone.