Immunolocalisation of nitric oxide synthase isoforms in the ductuli efferentes and epididym.

The present research used immunohistochemistry to analyse the detection and localisation of nitric oxide synthase (NOS) isoforms in the ductuli efferentes and epididymis of prepubertal and adult alpaca. In the ductuli efferentes and epididymis of prepubertal and adult animals, nNOS and eNOS were similarly expressed in epithelial lining cells, conversely differences were observed in the immunopresence of iNOS. Our data provide evidence that NOS isoforms may have roles in reproductive functions and in the developmental processes of the excurrent duct system in the alpaca.

Expression of nerve growth factor and its receptors in the uterus of rabbits: functional involvement in prostaglandin synthesis.

The aim of the present study was to evaluate: (1) the presence of nerve growth factor (NGF), neurotrophic tyrosine kinase receptor 1 (NTRK1), and nerve growth factor receptor (NGFR) in the rabbit uterus; and (2) the in vitro effects of NGF on PGF2α and PGE2 synthesis and on the PGE2-9-ketoreductase (PGE2-9-K) activity by the rabbit uterus. Nerve growth factor, NTRK1, and NGFR were immunolocalized in the luminal and glandular epithelium and stroma cells of the endometrium. reverse transcriptase polymerase chain reaction indicated the presence of messenger RNA for NGF, NTRK1, and NGFR in the uterus. Nerve growth factor increased (P < 0.01) in vitro secretions of PGF2α and PGE2 but coincubation with either NTRK1 or oxide nitric synthase (NOS) inhibitors reduced (P < 0.01) PGF2α production and blocked (P < 0.01) PGE2 secretion. Prostaglandins releases were lower (P < 0.01) than control when uterine samples were treated with NGF plus cyclooxygenase inhibitor. However, addition of NGFR inhibitor reduced (P < 0.01) PGF2α secretion less efficiently than NTRK1 or NOS inhibitors but had no effect on PGE2 yield. Nerve growth factor increased (P < 0.01) the activity of PGE2-9-K, whereas coincubation with NTRK1 or NOS inhibitors abolished (P < 0.01) this increase in PGE2-9-K activity. However, cotreatment with either cyclooxygenase or NGFR inhibitors had no effect on PGE2-9-K activity. This is the first study to document the distribution of NGF/NTRK1 and NGFR systems and their effects on prostaglandin synthesis in the rabbit uterus. NGF/NTRK1 increases PGF2α and PGE2 productions by upregulating NOS and PGE2-9-K activities, whereas NGF/NGFR augments only PGF2α secretion, through an intracellular mechanism that is still unknown.

Leptin receptor expression and in vitro leptin actions on prostaglandin release and nitric oxide synthase activity in the rabbit oviduct.

In this study, we have examined the presence and the distribution of receptors for leptin (Ob-R) in the oviduct of rabbits, and the effects of leptin on the release of prostaglandin (PG) F2alpha and PGE2 and on the activity of nitric oxide (NO) synthase (NOS) by oviducts cultured in vitro. Rabbits were killed during the follicular phase and the oviducts were incubated in vitro with leptin, PGF2alpha, PGE2, NO donor and inhibitors of NOS and cyclo-oxigenase (COX). Using immunohistochemistry, Ob-R-like positive reaction was observed only in the cytoplasm of secretory cells, having stronger intensity in the infundibulum and ampulla tracts than in the isthmus. Both leptin and NO donor inhibited PGE2 release, whereas they enhanced PGF2alpha release; NOS inhibitor alone or with leptin increased PGE2 and decreased PGF2alpha production; NOS activity was enhanced by leptin, while PGs did not affect this enzyme. This study suggests that the oviduct could be a potential target for endocrine regulation by leptin, whose circulating levels may act as a metabolic signal modulating oviductal PG release through mediation of the NOS/NO system.

Mammalian gonadotropin-releasing hormone increases PGF2 alpha production activating diacylglycerol lipase in Rana esculenta interrenal.

The aim of the present paper was to clarify if the prostaglandin F2 alpha (PGF2 alpha) production stimulated by mammalian gonadotropin-releasing hormone (mGnRH) comes from arachidonic acid (AA) freed by diacylglycerol (DAG) and/or membrane phospholipids in the interrenal of Rana esculenta. Interrenals of Rana esculenta were incubated with inhibitors of phospholipase A1 (PLA1), phospholipase A2 (PLA2), phospholipase C (PLC), protein kinase C (PKC) and diacylglycerol lipase (DAGlipase) in the presence or absence of mGnRH. In parallel, the same experiments were carried out using [3H]AA-labelled interrenals. The results of the experiments with non-labelled and [3H]AA-labelled interrenals were in agreement. PLA1, PLA2, PLC, PKC and DAGlipase inhibitors induced a decrease in PGF2 alpha production in interrenals without mGnRH, and PLA2 inhibitor was more effective than other inhibitors. PLC and DAGlipase inhibitors decreased the PGF2 alpha production by interrenals incubated with mGnRH, and PLC inhibitor was more effective than DAGlipase inhibitor. These findings suggest that the main source of AA used for mGnRH-induced PGF2 alpha synthesis is DAG; probably this decapeptide increases PGF2 alpha production enhancing the DAGlipase activity.

A novel neuropeptide cellular mechanism in amphibian interrenal steroidogenesis.

Interrenals of female Rana esculenta were incubated with gonadotropin-releasing hormone (GnRH), 9-ketoreductase inhibitor (palmitic acid), acetyl salicyclic acid, prostaglandin F2 alpha (PGF2 alpha), forskolin, isobutylmethyl xanthine (IBMX), dibutyril cyclic adenosine monophosphate (dbcAMP). Prostaglandin E2 (PGE2), PGF2 alpha, testosterone and 17 beta-estradiol were assessed on the incubation media. In addition, in the same interrenals, 9-ketoreductase and aromatase activities were evaluated. GnRH increased PGF2 alpha, 17 beta-estradiol, 9-ketoreductase and aromatase, and decreased PGE2 and testosterone. PGF2 alpha increased 17 beta-estradiol and aromatase, and decreased testosterone. Palmitic acid counteracted GnRH effects, while forskolin, IBMX and dbcAMP showed the same PGF2 alpha effects. These results suggest that GnRH stimulates 9-ketoreductase enhancing PGF2 alpha which in turn activates aromatase through cAMP mediation in the interrenal of Rana esculenta.

Amphibian oocyte: a model of a possible regulatory mechanism for prostaglandin E2 and prostaglandin F2 alpha synthesis.

To clarify the possible mechanisms regulating prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) synthesis, the effects of gonadotropin-releasing hormone (GnRH) and substance P (SP) on the release of these two prostaglandins were studied in the oocytes of the crested newt, Triturus carnifex. Full-grown oocytes of T. carnifex, freed from follicular cells, were incubated in the presence of GnRH or SP and of the inhibitors of several enzymes involved in the release of arachidonic acid (AA) and in the conversion of AA into PGE2 and PGF2 alpha. In parallel, the same experiments were performed on oocytes with membrane phospholipids labelled with [3H]AA. In addition, the PGE2-9-ketoreductase activity was evaluated through the conversion of [3H]PGE2 into [3H]PGF2 alpha. The results showed that GnRH and SP could regulate prostaglandin synthesis through the activation of phospholipase C and diacylglycerol lipase, and through the modulation of PGE2-9-ketoreductase in the oocytes of T. carnifex. In particular, GnRH enhances the activity of PGE2-9-ketoreductase with a consequent increase in PGF2 alpha, while SP inhibits the enzyme which leads to an increase in PGE2. A similar mechanism could also be hypothesized for other vertebrate species.

Possible mechanism for the first response to short captivity stress in the water frog, Rana esculenta.

To clarify the endocrine mechanism involved in the short captivity stress in the water frog, Rana esculenta, the activity of 9-ketoreductase, the enzyme which converts prostaglandin E2 (PGE2) into prostaglandin F2 alpha (PGF2 alpha), and aromatase, which converts testosterone into oestradiol-17 beta, were studied. Adult male and female frogs were sacrificed 0, 1.5, 3, 6, 12, 24, 48, 72, 168 and 336 h after capture in the field. PGE2, PGF2 alpha, progesterone, testosterone, oestradiol-17 beta and corticosterone plasma levels were detected by RIA at each time point. 9-Ketoreductase (conversion of [3H]PGE2 into [3H]PGF2 alpha) and aromatase (conversion of [3H]testosterone into [3H]oestradiol-17 beta) activities in the brain, testis, ovary and interrenal were also determined at each time point. After capture, levels of plasma PGF2 alpha increased (male: 228%; female: 288%) and PGE2 decreased (male: 68%; female: 81%) at 1.5 h, oestradiol-17 beta increased (male: 399%; female: 425%) and testosterone decreased (male: 87%; female: 83%) at 6 h, and corticosterone increased (male: 421%; female: 426%) at 72 h. 9-Ketoreductase activity in the brain was enhanced at 1.5 h after capture (male: 249%; female: 262%); aromatase activity increased at 6 h in the testis (261%), ovary (273%) and interrenal (male: 227%; female: 267%). These results indicate that short captivity stress could induce an increase in plasma PGF2 alpha through activation of brain 9-ketoreductase. In turn, PGF2 alpha might enhance the levels of circulating oestradiol-17 beta through activation of gonadal and interrenal aromatase.

Effects of beta-endorphin and naloxone on corticosterone and cortisol release in the newt (Triturus carnifex): studies in vivo and in vitro.

The effects of beta-endorphin and its receptor antagonist, naloxone, on corticosterone and cortisol production in male and female Triturus carnifex were studied in vivo and in vitro. In the in-vivo experiment, the animals were injected s.c. with beta-endorphin and/or naloxone, and killed after 15, 30, 90 and 360 min. In the in-vitro experiment, interrenal tissues, with and without added pituitary, were incubated with beta-endorphin and/or naloxone for 15, 30, 60 and 120 min. The data obtained in vivo and in vitro from males and females were in agreement. Treatment with beta-endorphin caused a significant decrease in corticosterone and cortisol release, while naloxone induced an increase in the two corticosteroids at the same times as the decrease caused by beta-endorphin. The combined beta-endorphin plus naloxone treatment did not change corticosterone and cortisol levels. These results suggest that, in Triturus carnifex, opioids are involved in the regulation of the hypothalamo-pituitary-interrenal axis. In particular, the in-vitro results indicate a direct effect of opioids on interrenal steroidogenesis.

Nitric oxide synthase activity and progesterone release by isolated corpora lutea of rabbits in the early and mid-luteal phases of pseudopregnancy are modulated differently by prostaglandin E-2 and prostaglandin F-2alpha via adenylate cyclase and phospholipase C.

By examining in vitro the effects of prostaglandin E-2 (PGE-2) and prostaglandin F-2alpha (PGF-2alpha) induced in the corpora lutea (CL) of pseudopregnant rabbits, we have demonstrated that these prostaglandins modulate luteal nitric oxide synthase (NOS) activity and progesterone production differently, depending on the age of the CL. On CL obtained on day 4 of pseudopregnancy (day-4), PGE-2 was found to depress NOS total activity to 13% of control and to significantly increase basal progesterone secretion by 61%, while PGF-2alpha had no effect. On day-9 CL, PGE-2 was ineffective, but PGF-2alpha caused a 2.5-fold increase of NOS activity and a marked decrease in progesterone production. Using specific inhibitors, we found that the regulatory actions of PGE-2 in vitro are mediated via the adenyl cyclase/protein kinase A (PKA) second messenger system, while the PGF-2alpha-induced luteolytic effects on day-9 CL depend upon activation of the phospholipase C/protein kinase C (PKC) system. The different responsiveness of day-4 and day-9 CL to PGE-2 and PGF-2alpha could depend on receptor availability for these two prostaglandins, even if other cellular mechanisms cannot be excluded. The present study supports a functional role for NOS in regulating the steroidogenic capacity of rabbit CL, and reveals a novel interaction between a stimulatory G-protein-coupled receptor and PKC/PKA-mediated signal transduction modulating NOS activity.

Nitric oxide synthase acutely regulates progesterone production by in vitro cultured rabbit corpora lutea.

We examined the presence and the regulation of nitric oxide (NO) synthase (NOS) using in vitro cultured corpora lutea (CL) obtained from rabbits at days 4 and 9 of pseudopregnancy. The role of NO and NOS on steroidogenesis was also investigated using the same CL preparations after short-term incubations (30 min and 2 h) with the NO donor, sodium nitroprusside (NP), the NOS inhibitor, Nomega-nitro-l-arginine methyl ester (l-NAME) and prostaglandin (PG) F-2alpha. The basal NOS activity was greater in CL at day 4 than at day 9, and was also differently modulated by PGF-2alpha, depending on the age of the CL. The addition of PGF-2alpha to day 4 CL had no effect, but PGF-2alpha on day 9 caused a threefold increase in NOS activity. NP caused a two- to fivefold decrease in release of progesterone from CL of both ages, and this inhibitory effect on steroidogenesis was reversed by l-NAME. All treatments failed to modify basal androgens and 17beta-oestradiol was not detectable in either control or treated CL. These results suggest that NO is effectively involved in the regulation process of steroidogenesis, independently of 17beta-oestradiol. PGF-2alpha had no effect on day 4, but induced luteolysis on day 9, by reducing progesterone (P

Prostaglandin receptors and role of G protein-activated pathways on corpora lutea of pseudopregnant rabbit in vitro.

Studies were conducted to characterize receptors for prostaglandin (PG) F(2alpha) (PGF(2alpha)) and PGE(2), and the signalling pathways regulating total nitric oxide synthase activity and progesterone production in rabbit corpora lutea (CL) of different luteal stages. CL were obtained at days 4, 9 and 13 of pseudopregnancy and cultured in vitro for 2 h with PGF(2alpha) or PGE(2) and with activators and inhibitors of G protein (Gp), phospholipase C (PLC), protein kinase C (PKC), adenylate cyclase (AC) and protein kinase A (PKA). High affinity PGF(2alpha) receptor (K(d)=1.9+/-0.6 nM mean+/-s.e.m. ) concentrations increased (P< or =0.01) four- to five-fold from early to mid- and late-luteal phases (50.6+/-8.5, 188.3+/-36.1 and 231.4+/-38.8 fmol/mg protein respectively). By contrast, PGE(2) receptor (K(d)=1.6+/-0.5 nM) concentrations decreased (P< or =0.01) from day 4 to day 9 and 13 (27.5+/-7.7, 12.4+/-2.4 and 16.5+/-3.0 fmol/mg protein respectively). The Gp-dependent AC/PKA pathway was triggered only on day 4 CL, mimicking the PGE(2) treatment and increasing progesterone production. In both day 9 and day 13 CL, the Gp-activated PLC/PKC pathway evoked a luteolytic effect similar to that induced by PGF(2alpha). The time-dependent selective resistance to PGF(2alpha) and PGE(2) by rabbit CL is mediated by factors other than a lack of luteal receptor-ligand interactions.

Expression patterns of endothelial and inducible nitric oxide synthase isoforms in corpora lutea of pseudopregnant rabbits at different luteal stages.

Total activity of nitric oxide (NO) synthase (NOS) and expression of both endothelial (eNOS) and inducible (iNOS) isoforms were examined in corpora lutea (CL) of rabbits across pseudopregnancy by quantitative RT-PCR analysis, Western blot and immunohistochemistry. CL were collected at early- (day 4), mid- (day 9) and late- (day 13) luteal phases of pseudopregnancy. The PCR product of rabbit luteal eNOS was cloned and its direct sequence exhibited 90% homology with those of other species. The steady-state mRNA levels encoding eNOS remained fairly constant throughout both early- and mid-luteal stages of pseudopregnancy but dropped almost to half (P

Presence of pituitary adenylate cyclase-activating polypeptide 38-immuno-like material in the brain and ovary of the female crested newt, Triturus carnifex: its involvement in the ovarian synthesis of prostaglandins and steroids.

The presence of pituitary adenylate cyclase-activating peptide (PACAP) 38-immuno-like material (PACAP 38-IL) in the brain and ovary of the crested newt, Triturus carnifex, and its action on ovarian steroidogenesis and prostaglandin synthesis were evaluated. The HPLC, brain and ovary extract peaks that eluted like PACAP 38 were considered PACAP 38-like material. The concentrations of PACAP 38-II in the HPLC extracts were measured by RIA. T. carnifex ovary was incubated with PACAP 38, brain and ovary PACAP 38-IL, and inhibitors of cyclooxygenase (COX), adenylate cyclase (AC) and phospholipase C (PLC) for 30 and 60 min. PACAI 38, and brain and ovary PACAP 38-IL increased prostaglandin E2 (PGE2) (30 and 60 min), and progesterone and corticosterone (60 min), but decreased oestradiol-17 beta (60 min). COX and PLC inhibitors counteracted the increases in PGE2, progesterone and corticosterone and the decrease in oestradiol-17 beta, and the AC, inhibitor also counteracted them except for PGE2. These results suggest that PACAP 38-IL, present in T. carnifex brain and ovary, acts on PLC, inducing the increase of PGE2 which, in turn, acting on AC, induces increases in progesterone and corticosterone and a decrease in oestradiol-17 beta.

Hormonal and cellular brain mechanisms regulating the amplexus of male and female water frog (Rana esculenta).

The role of nitric oxide (NO) synthase, prostaglandin E2-9-ketoreductase, and aromatase brain activities in regulating frog amplexus was assessed in the water frog (Rana esculenta). Plasma concentrations of testosterone were higher, and concentrations of 17beta-oestradiol lower, in amplexing males than in unamplexing males; while concentrations of testosterone and PGE2 were lower, and those of 17beta-oestradiol and PGF2alpha higher, in amplexing females compared to unamplexing females. Hormone release rescued from frog brains in vitro mirrored plasma hormone measures. Brain aromatase activity was lower in amplexing males; NO synthase was lower and PGE2-9-ketoreductase and aromatase were higher in amplexing females. In male brains, PGE2-9-ketoreductase inhibitor decreased PGF2alpha release and increased that of PGE2; aromatase inhibitor decreased 17beta-oestradiol and increased testosterone release. In female brains, NO donor and PGE2-9-ketoreductase inhibitor increased testosterone and PGE2 release and decreased that of 17beta-oestradiol and PGF2alpha; NO synthase inhibitor decreased testosterone release and PGE2 and increased 17beta-oestradiol and PGF2alpha release; PGF2alpha decreased testosterone release and increased 17beta-oestradiol release; aromatase inhibitor decreased 17beta-oestradiol release and increased testosterone release. In female brains, NO donor and PGE2-9-ketoreductase inhibitor decreased PGE2-9-ketoreductase and aromatase activities; PGF2alpha increased aromatase activity; NO synthase inhibitor increased PGE2-9-ketoreductase and aromatase activity. The data suggest that, in amplexing female brains, external and/or internal stimuli inhibit NO synthase, decreasing NO and activating PGE2-9-ketoreductase; in turn, PGF2alpha increases aromatase activity and 17beta-oestradiol release; while, in amplexing male brains, stimuli inhibit aromatase activity, thereby increasing testosterone production.

Nitric oxide mediates gonadotropin-releasing hormone effects on frog pituitary.

We studied the possible role of nitric oxide (NO) in GnRH-induced gonadotropin secretion in the female water frog, Rana esculenta. During pre-reproduction, pre-ovulation, ovulation, post-ovulation, refractory, recovery and hibernation, pituitaries were incubated with medium-alone, GnRH, NO donor (NOd), NO synthase inhibitor (NOSi), cyclic GMP analogue (cGMPa), soluble guanylate cyclase inhibitor (sGCi), GnRH plus NOSi, GnRH plus sGCi, and NOd plus sGCi. Because antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on ovarian progesterone secretion. The ovaries were superfused with the pituitaries pre-incubated as reported above. In addition, NOS activity and cGMP levels were determined in the pre-incubated pituitaries. Those pre-incubated with medium-alone and with GnRH increased progesterone secretion during pre-reproduction, pre-ovulation, ovulation and recovery; the increase induced by GnRH was higher than that induced by medium-alone during pre-reproduction, pre-ovulation and recovery. NOd and cGMPa increased progesterone in all considered reproductive phases except ovulation; the increase induced by NOd and cGMP was higher than that induced by medium-alone during pre-reproduction, pre-ovulation and recovery. NOS activity was highest during ovulation and lowest during post-ovulation, refractory and hibernation. GnRH increased NOS activity during pre-reproduction, pre-ovulation and recovery. Cyclic GMP levels were highest during ovulation and lowest during post-ovulation, refractory and hibernation. GnRH increased cGMP levels during pre-reproduction, pre-ovulation and recovery, NOd during all considered reproductive phases. These results suggest that NO mediates basal and GnRH-induced gonadotropin secretion in female Rana esculenta.

Substance P downregulates basal and gonadotropin-releasing hormone-induced gonadotropin in vitro secretion by pituitary gland of crested newt, Triturus carnifex.

The possible role of Substance P (SP) was studied in the modulation of basal and gonadotopin-releasing hormone (GnRH)-induced gonadotropin secretion in the urodele crested newt, Triturus carnifex. During prereproduction, reproduction (noncourtship and courtship), refractory, recovery and aestivation, male and female pituitaries were incubated with medium-alone, GnRH, SP, GnRH receptor antagonist (antide), and SP receptor antagonist (L-703606). Since antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on the secretion of testicular androgens and ovarian progesterone from gonads superfused with the preincubated pituitaries. Pituitaries of both sexes preincubated with medium-alone, GnRH, GnRH plus L-703606, and GnRH plus SP plus L-703606 increased steroid secretion during prereproduction, noncourtship, courtship, and recovery; the increase induced by the pituitaries incubated with medium-alone was lower during prereproduction, noncourtship, and recovery. Pituitaries preincubated with SP, GnRH plus SP, GnRH plus SP plus antide, and SP plus antide did not change basal steroid secretion in any of the reproductive phases considered. Antide, L-703606, GnRH plus antide, GnRH plus SP plus antide plus L-703606, SP plus L-703606, and antide plus L-703606 experimental groups showed the same results as those with medium-alone. These results suggest that SP downregulates gonadotropin release in both Triturus carnifex sexes. In addition, an antagonist role, through receptor-independent mechanisms, exists between GnRH (upregulation) and SP (downregulation) in the modulation of pituitary.

Changes in refractoriness of rabbit corpora lutea to a prostaglandin F2 alpha analogue, alfaprostol, during pseudopregnancy.

The responsiveness of rabbit corpus luteum to 200 micrograms of the prostaglandin F2 alpha (PGF2 alpha) analogue, alfaprostol, between Days 3 and 9 of pseudopregnancy was assessed by evaluating the decline in plasma progesterone after treatment with PGF2 alpha in 81 New Zealand White (NZW) rabbits. On Days 3-5, functional luteolysis was not observed. On Days 6, 7, and 8 of pseudopregnancy, the number of rabbits responsive to PGF2 alpha, rose from 38% to 71% and 83%, respectively. In the other cases, the effect of the PGF2 alpha analogue was transient as CL recovered in the following 2 or 3 days. By contrast, on Day 9 luteolysis was effective and persistent in all the animals. In rabbits treated on Day 9, progesterone decreased gradually from 10.6 +/- 0.7 within the first 6 h, but fell to 3.6 +/- 1.5 ng/mL (p < 0.01) 12 h after PGF2 alpha and to 0.2 +/- 0.1 ng/mL (p < 0.01) 24 h later.

Role of nitric oxide in gonadotropin-releasing hormone-dependent prostaglandin F2 alpha synthesis by frog (Rana esculenta) interrenal gland during post-reproduction.

The aim of this study was to clarify the possible involvement of nitric oxide (NO) on prostaglandin (PG) E2-9-ketoreductase activity in the gonadotropin-releasing hormone (GnRH)-dependent PGF2 alpha synthesis by the interrenal gland of the female water frog, Rana esculenta, during the post-reproduction. Interrenal glands were incubated in vitro with GnRH, NO donor (sodium nitroprusside, SNP), and inhibitors of phospholipase C (compound 48/80), inositol triphosphate (decavanadate), calmodulin (calmidazolium), NO synthase (L-NAME), and PGE2-9-ketoreductase (palmitic acid). Production of PGE2 and PGF2 alpha and NO synthase and PGE2-9-ketoreductase activities were determined. GnRH and SNP increased PGF2 alpha production and PGE2-9-ketoreductase activity, and decreased production of PGE2 and GnRH increased NO synthase activity. GnRH effects were blocked by all inhibitors, except for palmitic acid, which did not affect NO synthase activity, which is increased by GnRH. This study indicates that NO may be involved in regulation of the R. esculenta post-reproduction through stimulation of PGE2-9-ketoreductase activity in GnRH-dependent PGF2 alpha synthesis by the frog interrenal gland.

Expression of the cannabinoid receptor type 1 in the pituitary of rabbits and its role in the control of LH secretion.

The aim of this study was to elucidate the possible direct regulatory role of the endocannabinoids in the modulation of LH secretion in rabbits, a reflex ovulator species. The cannabinoid receptor type 1 (CB1) was characterized by RT-PCR techniques in the anterior pituitary of intact and ovariectomized does treated with GnRH and primed with estrogen and CB1 antagonist, rimonabant. Cannabinoid receptor type 1 immune reaction was evidenced by immunohistochemistry in the cytoplasm of approximately 10% of the pituitary cells with a density of 8.5 ± 1.9 (per 0.01 mm(2)), both periodic acid-Schiff positive (30%) and negative (70%). All CB1-immunoreactive cells were also immune reactive for estrogen receptor type 1. Ovariectomy, either alone or combined with estrogen priming, did not modify the relative abundances of pituitary CB1 mRNA, but decreased (P < 0.01) the expression of estrogen receptor type 1 mRNA. Treatment with CB1 antagonist (rimonabant) inhibited (P < 0.01) LH secretory capacity by the pituitary after GnRH injection, and estrogen priming had no effect. The present findings indicate that the endocannabinoid system is a potential candidate for the regulation of the hypothalamic-pituitary-ovarian axis in reflex ovulatory species.

Immunolocalization, gene expression, and enzymatic activity of cyclooxygenases, prostaglandin e2-9-ketoreductase, and nitric oxide synthases in Mediterranean buffalo (Bubalus bubalis) corpora lutea during diestrus.

Immunopresence, gene expression, and enzymatic activity of cyclooxygenase 1 (COX1), COX2, PGE2-9-ketoreductase (PGE2-9-K), endothelial (eNOS), and inducible nitric oxide synthases (iNOS), and hormone in vitro production were examined in early, mid, late, and regressive buffalo corpora lutea (CL). COX1 immunosignals were detected in the cytoplasm of small luteal cells, COX2 in large luteal cells, and PGE2-9-K in all luteal cells. COX2 and PGE2-9-K immunosignals were greater in late CL. Immunopresence of both NOS types were evidenced in the nuclei and cytoplasm of all luteal cells, as well as in the nuclei of endothelial cells, during all stages studied. The eNOS and iNOS immunosignals increased during the early stage. COX1 transcripts were lower in late and regressive CL, COX2 in late, PGE2-9-K higher in regressive, and iNOS higher in early and lower in regressive CL. COX1 enzymatic activity was lower in regressive CL, COX2 increased in mid and late stages, and PGE2-9-K was higher in late CL. Endothelial NOS activity was higher during mid and late stages and lower in regressive, whereas iNOS was greater in late and lower in early. Progesterone in vitro release was higher in mid and lower in late phase, while PGF2α synthesis was higher in late CL and lower in regressive, and PGE2 was higher during regressive stage. These results support the idea that COX, NOS, and PGE2-9-K regulate buffalo CL life span. In particular, regressive CL seems involved in the development of the contralateral early CL, through the production of the luteotrophic PGE2.