The effects of hypokalaemia on the hormone exocytosis in adenohypophysis and prolactinoma cell culture model systems

The extracellular ion milieu determines the exocytosis mechanism that is coupled to spontaneous electrical activity. The K(+) ion plays crucial role in this mechanism: as the potassium current is associated with membrane hyperpolarization and hormone release through protein cascade activation. The primary aim of this study was to investigate the response mechanisms of normal adenohypophysis and adenohypophyseal prolactinoma cell populations at different extracellular K(+) levels with an otherwise isoionic milieu of all other essential ions. We focused on prolactin (PRL) and adrenocorticotrophic hormone (ACTH) release.In our experimental study, female Wistar rats (n=20) were treated with estrone-acetate (150 μg/kg b.w./week) for 6 months to induce prolactinomas in the adenohypophysis. Primary, monolayer cell cultures were prepared by enzymatic and mechanical digestion. PRL and ACTH hormone presence was measured by radioimmunoassay or immuno-chemiluminescence assay. Immunocytochemistry was used to assess the apoptotic cells.Differences between the effects of hypokalaemia on normal adenohypophysis cultures and prolactinoma cell populations were investigated. Significant alteration (p<0.001, n=10) in hormone exocytosis was detected in K(+) treated adenohypophyseal and prolactinoma cell cultures compared to untreated groups. Immunocyto-chemistry showed that Bcl-2 expression was reduced under hypokalaemic conditions.The decrease in hormone exocytosis was tightly correlated to the extracellular K(+) in both cell types, leading to the conclusion that external K(+) may be the major factor for the inhibition of hormone release. The significant increase in hormone content in supernatant media suggests that hypokalaemia may play important role in apoptosis.

Effects of galanin-monoaminergic interactions on vasopressin secretion in rat neurohypophyseal cell cultures

The effects of dopamine (DA), serotonin (5-HT), histamine (HA), adrenaline (ADR), noradrenaline (NADR) and K(+) administration on vasopressin (VP) secretion were studied in 13-14-day cultures of rat neurohypophyseal (NH) cells, and it was examined whether galanin (GAL) can modify the VP release enhancement induced by these monoaminergic compounds. An enzymatic dissociation technique was used to make the rat NH cell cultures. The VP contents of the supernatants of 14-day cultures were determined by radioimmunoassay. Following the administration of 10(-6) M GAL, the VP secretion into the supernatant media decreased. DA, 5-HT, ADR or NADR treatment increased the VP level substantially, while the enhancing effect of HA was more moderate. GAL administration before DA, ADR and NADR treatment prevented the VP concentration increase induced by DA, ADR or NADR. Preincubation with GAL reduced the 5-HT- or HA-induced VP level increases; the VP concentrations of the supernatant media remained above the control level. The GAL blocking effect was prevented by previous treatment with the GAL receptor antagonist galantid (M15). GAL had no effect on the VP level increase induced by K(+), which causes a non-specific hormone secretion. The results indicate that the changes in VP secretion induced by the monoaminergic system can be directly influenced by the GAL-ergic system. The interactions between the monoaminergic and GAL-ergic systems regarding VP secretion occur at the level of the posterior pituitary.

Histamine-induced enhancement of vasopressin and oxytocin secretion in rat neurohypophyseal tissue cultures

The effects of histamine (HA) on vasopressin (VP) and oxytocin (OT) secretion were studied in 13-14-day cultures of isolated rat neurohypophyseal (NH) tissue. The VP and OT contents of the supernatant were determined by radioimmunoassay (RIA) after a 1 or 2-h incubation. Significantly increased levels of VP and OT production were detected in the tissue culture media following HA administration, depending on the HA dose. The elevation of NH hormone secretion could be partially blocked by previous administration of the HA antagonist mepyramine (MEP, an H1 receptor antagonist) or cimetidine (CIM, an H2 receptor antagonist). Thioperamide (TPE, an H3-H4 receptor antagonist) did not influence the VP or OT secretion increase induced by HA. The application of MEP, CIM or TPE after HA administration proved ineffective. The H1 and H2 receptors are mainly involved in the HA-induced increase of both VP and OT secretion in isolated NH tissue cultures. The results indicate that NH hormone release is influenced directly by the histaminergic system, and the histaminergic control of VP and OT secretion from the NH tissue in rats can occur at the level of the posterior pituitary.

Serotonin-induced enhancement of vasopressin and oxytocin secretion in rat neurohypophyseal tissue culture

The effects of serotonin (5-hydroxytryptamine; 5-HT) on vasopressin (VP) and oxytocin (OT) secretion were studied in 13-14-day cultures of isolated rat neurohypophyseal (NH) tissue. The VP and OT contents of the supernatant were determined by radioimmunoassay after a 1 or 2 h incubation. Significantly increased levels of VP and OT production were detected in the tissue culture media following 5-HT administration, depending on the 5-HT dose. The elevation of NH hormone secretion could be partially blocked by previous administration of the 5-HT antagonist ketanserin or metergoline. WAY-100635 did not influence the increased VP secretion induced by 5-HT, but the elevated OT production was prevented by WAY-100635 before 5-HT administration. The application of WAY-100635, ketanserin or metergoline, after 5-HT administration proved ineffective. The results indicate that NH hormone release is influenced directly by the serotonergic system. The serotonergic control of VP and OT secretion from the NH tissue in rats can occur at the level of the posterior pituitary.

Inhibitory effect of galanin on dopamine induced increased oxytocin secretion in rat neurohypophyseal tissue cultures

The regulation of oxytocin (OT) release by galanin (GAL) at the neurohypophyseal (NH) nerve terminal is not adequately understood. The effect of GAL on the secretion of OT was studied in 13- to 14-day cultures of isolated rat NH tissue. By this time, the hormone content of the medium had become constant. The OT content of the supernatant medium was determined by RIA after a 1- or 2-h incubation. A significantly decreased content of OT was found following incubation with 10(-6)-10(-8) M doses of GAL. Dopamine (DA) and the DA-active drugs apomorphine (APM) and Pro-Lys-Gly (PLG) (10(-6) M in each medium) increased the OT synthesis of NH tissue cultures. This elevation of OT secretion could be blocked by the administration of GAL together with DA, APM or PLG. The DA-blocking effect of GAL was prevented by previous treatment with the GAL receptor antagonist galantid (M15). The results indicate that OT release from the NH is directly influenced by the GAL-ergic system. The GAL-ergic control of OT secretion from NH tissue in rats can occur at the level of the posterior pituitary.

Inhibitory effect of galanin on dopamine-induced enhanced vasopressin secretion in rat neurohypophyseal tissue cultures

The effect of galanin (GAL) on vasopressin (VP) secretion was studied in 13-14-day cultures of isolated rat neurohypophyseal (NH) tissue. The VP content of the supernatant was determined by radioimmunoassay (RIA) after a 1- or 2-h incubation. A significantly decreased content of VP was detected following the administration of 10(-6)-10(-9) M doses of GAL. Dopamine (DA) and the DA-active drugs apomorphine (APM) and Pro-Lys-Gly (PLG) (10(-6) M in each medium) increased the VP level of NH tissue cultures. This VP concentration elevation could be blocked by the administration of GAL together with DA, APM or PLG. The DA-blocking effect of GAL was prevented by previous treatment with the GAL receptor antagonist galantid (M15). The results indicate that VP release is directly influenced by the GAL-ergic system. The GAL-ergic control of VP secretion from NH tissue in rats can occur independently of the hypothalamus, at the level of the posterior pituitary.

Effects of dopamine and dopamine-active compounds on oxytocin and vasopressin production in rat neurohypophyseal tissue cultures

The effects of dopamine (DA) or DA-active drugs on the synthesis of neurohypophyseal (NH) hormones were studied in 13-14 day cultures of isolated NH tissue from rats. The following DA-active compounds were used (10(-6) M in each medium): DA, apomorphine (APM), Pro-Lys-Gly (PLG), butaclamol (B), haloperidol (HP), chlorpromazine (CPZ) and sulpiride (SP). The oxytocin (OT) and vasopressin (VP) contents of the condensed media were determined by RIA after a 1 or 2 h incubation. Significantly increased contents of OT and VP were detected in the tissue culture media following DA, APM or PLG administration. This elevation of NH hormone production could be blocked by previous administration of B or the DA receptor antagonists HP, CPZ or SP. The application of B after DA agonists proved ineffective. The results indicate that NH hormone production can be directly influenced by the DA-ergic system. The DA-ergic control of NH hormone secretion in rats can occur independently of the hypothalamus, at the level of the posterior pituitary.

Vasopressin pressor receptor-mediated activation of HPA axis by acute ethanol stress in rats

The plasma arginine vasopressin (AVP), ACTH, and corticosterone levels and the hypothalamic corticotropin-releasing hormone (CRH) content were measured after oral administration of 1 ml of 75% ethanol to rats, a model known to induce acute gastric erosions and stress. Elevated plasma AVP, ACTH, and corticosterone levels were detected 1 h after ethanol administration. Treatment with the vasopressin pressor (V(1)) receptor antagonist [d(CH(2))(5)Tyr(Me)-AVP] before ethanol administration significantly reduced the ACTH and corticosterone level increases. A higher hypothalamic CRH content was measured at 30 or 60 min after ethanol administration. V(1) receptor antagonist injection, 5 min before ethanol administration, inhibited the rise in hypothalamic CRH content. The protein synthesis blocker cycloheximide prevented the hypothalamic CRH content elevation after stress. The AVP-, CRH-, and AVP + CRH-induced in vitro ACTH release in normal anterior pituitary tissue cultures was also prevented by pretreatment with the V(1) receptor antagonist. The results support the hypothesis that stress-induced AVP may not only act directly on the ACTH producing anterior pituitary cells but also indirectly at the hypothalamic level via the synthesis and release of CRH.

Functional membrane changes due to tumor induction in rat pituitary cell cultures

Membrane functions in tumorous cells are different from those in healthy cells. The aim of the present study was to investigate the changes in pituitary cell membrane functions and hormone secretion after tumor induction in vivo and in vitro. Prolactinomas were induced in vivo in female Wistar rats with estrone acetate. Normal anterior pituitaries and prolactinomas of female Wistar rats were dissociated enzymatically and mechanically, then cultured on collagen-treated plastic dishes. Some normal anterior pituitary cultures were treated with benz(c)acridines as tumorigenic agents in vitro. Intracellular 3',5'-cyclic-adenosine monophosphate (cAMP) levels were determined by a competitive binding technique, membrane fluidity was assayed by fluorescence anisotropy, and ATP-ase activities were estimated via ATP loss. The results indicated decreased membrane fluidity in tumorous cell cultures. However, in vitro benz(c)acridine treatment exerted more pronounced effects than those observed after in vivo estrone treatment. The ATP-ase activities were highly increased in benz(c)acridine-treated cells and in estrogen-induced prolactinoma cells, more strongly so in the former ones. The intracellular cAMP levels were higher than normal in both of them. The results concerning the ACTH, alpha-MSH, PRL and GH levels of normal and tumorous cell cultures were published in our previous study. Our findings show that the tumorous transformation of pituitary cells can cause significant changes in functional membrane parameters and hormone secretion. Decreased membrane fluidity was accompanied by an increased exocytosis (hormone release) and adenylate cyclase activity in tumorous cells.

Primary mono-layer cell cultures as model system for studying of environmental toxic agents: organochlorine compounds

Organic pollution of water and soil has various harmful effects on biological systems (1). Chlorine substituted benzol compounds are one these xenobiotic substances, which are toxic to the environment (2). They can also accumulate in plant and animal tissues (3), which provides ample reason to study the effects of sublethal doses of chloro-benzols on various cell cultures. In this study the toxic effects of chloro-benzols were investigated on avian fibroblast and mammalian hepatocyte cultures. The fibroblast cultures were prepared from eggs preadapted to chloro-benzol during a fourteen-day-long incubation period. The Wistar rat hepatocyte monolayer cultures were exposed to a direct treatment of 1,2,4-tri-chloro-benzol (0.01 microgram/ml-1 microgram/ml) for 3 hours. Following the treatment with chloro-benzol, the viability of the cells was measured, together with lactic dehydrogenase activity, in both kinds of cultures. The effect of tri-chloro-benzol treatment on chicken eggs was not significant. The cells of chicken embryos were not damaged after the 1,2,4-tri-chloro-benzol treatment. The hepatocyte cultures showed the toxic effects of 1,2,4-tri-chloro-benzol after the direct and acute treatment. The cell viability decreased and the LDH activity increased significantly. These results show that the primary cell cultures are suitable for studying the effects of organochlorine compounds.

Identification of oxytocin and vasopressin from neurohypophyseal cell culture

Our observation that dispersed cultures of neurohypophysis obtained from adult rats are capable of synthesizing and releasing oxytocin and vasopressin is unexpected, because in whole animals these hormones are known only to be stored, not to be produced in the posterior lobe of the pituitary. The hormone content of cell culture medium was elevated from 0 to 129 +/- 14 pg/mg protein for oxytocin and from 0 to 42 +/- 4 pg/mg protein for vasopressin during two weeks as determined by specific radioimmunoassay. By molecular mass and structure determination (tandem mass spectrometry) we have proved that the supernatant of the cell cultures contains not only immunologically but mass spectrometrically identified neurohypophyseal hormones.

Adenomatous leydig cell hyperplasia of the testicle remnant after subtotal orchidectomy in the rat

Subtotal orchidectomy is a suitable method to induce adenomatous Leydig cell hyperplasia in the testicular remnant without irradiation or toxic chemicals. Very expressed hyperplasia of the smooth endoplasmic reticulum was detectable electronmicroscopically in the newly formed Leydig cells. The activity of Δ⁵-3β-hydroxysteroid dehydrogenase in the homogenate of the testicular remnant was found considerably elevated. These observations suggest a steroidogenetic activity of the proliferating Leydig cells.

Central effects of tricyclic compounds on the endocrine system--an in vitro study

The present study involves the effects on corticotropin (ACTH) release of neuro- and thymoleptic tricyclic antidepressant compounds (TrcACs: chlorpromazine, promethazine, haloperidol, imipramine, amitriptyline) and their interactions with lysine-8-vasopressin (LVP) and corticosterone (B). As an in vitro model, 14-day monolayer pituitary cell cultures of Wistar rats were employed. The ACTH concentrations of the supernatant media were measured by radioimmunoassay. TrcACs augmented ACTH release; their combination with LVP, however, did not result in further stimulation; moreover, when combined with TrcACs + LVP, B did not inhibit, but rather paradoxically increased their ACTH-releasing action. As none of these phenomena were followed by relevant changes in intracellular cyclic adenosine monophosphate content, the mechanism of action may be proposed to involve a protein kinase C route.

Inhibition of bacterial plasmid replication by stereoselective binding by tricyclic psychopharmacons

Several dibenzazepines, thioxanthene, and phenothiazine stereoisomers were studied for their abilities to inhibit plasmid replication, intracellular transfer of R-plasmid, bacterial ATP-ase, and mouse serum cholinesterase isoenzyme. Partially saturated derivative of desipramine inhibited plasmid replication and transfer, but the fully saturated derivative was inactive. The inhibition of plasmid curing and transfer patterns did not correlate with the inhibition of ATP-ase and cholinesterase. Trans-clopenthixol was more effective in plasmid elimination than the cis-isomer. On the other hand, the cis-isomer inhibited ATP-ase and cholinesterase more than the trans-isomer. The levo- and dextro-methoxytrimeprazine also inhibited plasmid replication and enzyme activity. We believe that the tricyclic configuration of the drugs tested for stereospecific binding to bacterial receptors is more important than its side chain orientation. We believe that there is a similarity between bacterial receptor sites and neural receptor sites. Therefore, this model may be useful in the study of neuropharmacological agents as potential antibacterial agents.