Biomedical subjects

W Wuttke

Publications and source records attributed to W Wuttke.

At least 109 records · Page 6Linked to original sources

PubMed1994

In vitro prolactin but not LH and FSH release is inhibited by compounds in extracts of Agnus castus: direct evidence for a dopaminergic principle by the dopamine receptor assay.

Women suffering from premenstrual mastodynia often respond to stimuli of prolactin (Prl) release with a hypersecretion of this hormone. Pharmacological reduction of Prl release by dopamine agonists or treatment with extracts of Agnus castus (AC) improve the clinical situation of patients with such premenstrual symptoms. Extracts of AC contain compounds which inhibit in vivo Prl release in women as well as in vitro from dispersed rat pituitary cells. It is yet unknown whether this inhibitory action of AC is only exerted on Prl release or whether release of other pituitary hormones like LH and FSH is also affected. The effects of AC on LH and FSH release were examined in vitro using rat pituitary cell cultures. To rule out that the Prl-inhibiting properties of AC are at least in part due to a cytotoxic component, pituitary cell cultures were subjected to the MTT test. To assess whether the Prl inhibitory effect of AC preparations is due to compounds acting as dopamine (DA) agonists, we used the corpus striatum membrane DA receptor binding assay. Our results demonstrate for the first time that AC extract contains an active principle that binds to the D2 receptor. Thus, it is very likely that it is this dopaminergic principle which inhibits Prl release in vitro from rat pituitary cells. Furthermore we give evidence for the specificity of action of AC on hormone release, since gonadotropin secretion remained unaffected. The findings of the present study support the therapeutical usefulness of AC extracts for treatment of premenstrual mastodynia which is associated with hypersecretion of Prl. Furthermore, the beneficial effects of AC appear to be due to the inhibition of pituitary Prl release.

Animals↗

PubMed1994

Effect of anaesthesia on the cytokine responses to abdominal surgery.

Plasma concentrations of interleukins, particularly IL-6, increase after trauma and surgery. We have undertaken this study to see if the choice of anaesthetic directly or indirectly influences cytokine release. Twenty women (ASA I-II, aged 26-60 yr) undergoing elective hysterectomy for non-malignant disease were allocated randomly to receive either inhalation anaesthesia with isoflurane and nitrous oxide (group 1), or total i.v. anaesthesia with alfentanil and propofol (group 2). Blood samples for measurement of interleukins IL-1 beta and IL-6, and cortisol and prolactin concentrations were obtained at intervals from before induction to 6 h after surgery. IL-1 beta concentrations did not change during the study. IL-6 increased significantly in both groups (P < 0.05). The IL-6 increase in group 1 began earlier than in group 2. Median IL-6 concentrations were greater in group 1 (median 62 (range 0-214) pg ml-1 vs 46 (0-220) pg ml-1) (P < 0.01). Cortisol concentrations increased more rapidly and reached greater maximum concentrations in group 1. Prolactin concentrations increased immediately and to the same degree after induction in both groups, but were greater in group 2 after operation. We conclude that anaesthesia with alfentanil and propofol diminished release of IL-6 in response to abdominal surgery compared with isoflurane and that this reduction was an effect of alfentanil.

Adult↗

PubMed1994

Blockade of noradrenergic neurotransmission with diethyldithiocarbamic acid decreases the mRNA level of gonadotropin-releasing hormone in the hypothalamus of ovariectomized, steroid-treated prepubertal rats.

We have previously found that progesterone (P) augmented gonadotropin-releasing hormone (GnRH) mRNA levels in the hypothalamus of ovariectomized, estradiol-treated (OVX + E) prepubertal rats. In order to determine whether noradrenergic neurotransmission is involved in the stimulatory effect of P on GnRH gene expression, diethyldithiocarbamic acid (DDC, 500 mg/kg), a dopamine beta-hydroxylase inhibitor was administered i.p. 1 h before P (1 mg) injection into OVX + E treated rats, and the effect of DDC on the P-induced GnRH mRNA levels was examined. A single injection of P into OVX + E primed rats augmented norepinephrine (NE) content, while the administration of DDC effectively blocked the P-induced increase in NE content, along with the increase in dopamine content. Suppression of NE neurotransmission with DDC resulted in a marked decrease in the P-induced GnRH mRNA levels as well as GnRH release in vitro. These results clearly demonstrate that noradrenergic neurotransmission is involved in P-stimulated GnRH gene expression in the rat hypothalamus.

Animals↗

PubMed1994

Effects of photoperiod and slow-release preparations of bromocryptine and melatonin on reproductive activity and prolactin secretion in female goats.

The present study was conducted to investigate seasonal reproductive patterns in a Boer Goat x German Fawn cross and ways to modulate these patterns by injecting slow-release bromocryptine and melatonin preparations. Twenty does were exposed to a light program of alternating periods of 90 long days (LD) followed by 100 short days (SD) twice in succession (LD1, SD1, LD2, SD2). At the beginning of LD2, does were treated as follows: vehicle injection (CTR, n = 7), slow-release bromocryptine (BCR, n = 6), or slow-release melatonin (MLT, n = 7). Blood samples were collected twice weekly, and from October 5 to December 14, 1989, weekly, to be analyzed for progesterone, prolactin, and melatonin. Long days inhibited cyclicity, and short days stimulated it. Prolactin was increased during long days and decreased during short days. High ambient temperature resulted in increased prolactin concentrations. Under long photoperiod, long-acting BCR suppressed prolactin secretion for 68 d, and the estrous season was extended compared with CTR. Under long photoperiod, long-acting MLT increased serum melatonin for 96 d, suppressed prolactin concentration, and substantially lengthened the period of cyclicity compared with the CTR- and BCR-treated groups. The resumption of cyclicity during the subsequent short day period occurred later in MLT- than in CTR- and BCR-treated groups. In conclusion, we modulated the day length-controlled seasonal cyclicity of goats by treating them with injectable slow-release preparations of BCR and MLT, the latter being more effective.

Animals↗

PubMed1993

Competitive PCR for quantitation of gonadotropin-releasing hormone mRNA level in a single micropunch of the rat preoptic area.

A competitive polymerase chain reaction (PCR) for quantitating gonadotropin-releasing hormone (GnRH) mRNA level in a single micropunch of the rat preoptic area (POA) is described. The POA (600 microns in depth) was micropunched from frozen rat brain slices and used for mRNA isolation using Dynabeads-oligo(dT) magnetic separation technique. The target RNA combined with a synthetic, deletion mutant GnRH cRNA as an internal standard, is co-reverse transcribed, and their cDNAs are subsequently co-amplified by Taq DNA polymerase in the same tube in which the same GnRH primers are used. This PCR protocol is sensitive enough to detect GnRH mRNA level in a single POA micropunch derived from an individual rat. There is a linear increase of the amount of GnRH PCR products as a function of input RNA and of the number of PCR cycles. Addition of mutant GnRH cRNA as an internal standard allows us to quantitate GnRH mRNA level in biological samples and to compensate variations of PCR reaction between samples. Following preoptic treatment with 5'-ADMP, which depletes selectively norepinephrine (NE), GnRH mRNA level was significantly reduced. This simple, yet highly sensitive PCR method appears to be a valuable tool for the study of the cellular and molecular regulation of GnRH gene expression in a variety of experimental models.

Animals↗

PubMed1993

Different steroidogenic response of young and aged porcine small and large luteal cells to prostaglandin F2 alpha, oxytocin and estradiol.

The role of oxytocin (OXT) and prostaglandin F2 alpha (PGF2 alpha) in the process of luteal regulation, particularly their function in the early luteal phase is poorly understood. Therefore the effects of both compounds on in vitro steroid release of porcine luteal cells harvested from young/middle-aged (day 4-6, day 0 = 1st estrous day) or old (day 12-14) corpora lutea were tested. As corpora lutea (CL) contain at least two different steroidogenic cell populations, fractions of the so called small (SLC) and large (LLC) luteal cells were prepared and tested in separate experiments. In SLC as well as LLC from young CL OXT and PGF2 alpha inhibited progesterone (P) production but induced a strong increase of estradiol (E2) release. In old SLC and LLC OXT and PGF2 alpha were still inhibitory to P release but OXT was ineffective and PGF2 alpha had a moderate stimulatory effect on luteal E2 secretion. In SLC cultures from young but not from old CL E2 exerted a powerful stimulatory effect on progesterone (P) secretion, i.e. E2 has strong luteotrophic effects in the early luteal phase. Indeed, the pronounced inhibitory effect of OXT and PGF2 alpha on P release from SLC could be counteracted by the addition of exogenous E2 to the culture media. Therefore, we suggest that in the early luteal phase OXT as well as PGF2 alpha have an indirect, E2-mediated luteotrophic effect on P release which is stronger than the direct inhibitory action on P secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

The stimulatory effect of pituitary adenylate cyclase activating polypeptide (PACAP) on LH release from rat pituitary cells in vitro does not involve calcium mobilization.

The hypothalamic peptide "pituitary adenylate cyclase activating polypeptide (PACAP)" stimulates cAMP production in cultured rat pituitary cells and enhances LH release. It has been suggested that the stimulation of LH release by PACAP comprises two distinct mechanisms: a direct stimulatory action on LH secretion and a potentiation of the response of the gonadotrophes to LHRH. Thus the possibility exists that PACAP may enhance LH secretion not only by increased cAMP production but also by increasing cytosolic Ca2+ concentrations ([Ca2+]). In the present study we examined whether PACAP affects cytosolic [Ca2+] in identified rat gonadotrophes (as determined by the fura-method) and whether the suggested potentiating effect of PACAP on LHRH induced LH release is dependent on Ca2+. PACAP (1 nM) and 0.1 nM LHRH significantly increased LH concentrations in the culture medium after 5 hrs of incubation. Coincubation of cells with both peptides resulted in an additive increase of LH release. While the stimulatory effect LHRH was blunted in Ca(2+)-free medium, PACAP remained stimulatory to LH release. PACAP stimulated cAMP formation regardless whether the culture medium contained Ca2+ or not. Gonadotrophes were selected by their response to LHRH (1 microM) and were subsequently challenged with PACAP (1 microM). About 75% of gonadotrophes responded also to PACAP with an increase of cytosolic [Ca2+] which was blunted by removal of extracellular Ca2+. We suggest that in the rat pituitary the majority of the gonadotrophes are PACAP responsive as determined by an increase of cytosolic [Ca2+].(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effects of angiotensin II and atrial natriuretic peptide on LH release are exerted in the preoptic area: possible involvement of gamma-aminobutyric acid (GABA).

The preoptic/anterior hypothalamic area (PO/AH) contains the majority of LHRH neurons of which the function is regulated by a variety of neurotransmitters and peptides. In this area, numerous estrogen-receptive neurons utilize gammaaminobutyric acid (GABA) as neurotransmitter and these neurons communicate directly with LHRH neurons. Angiotensin II (AII) and atrial natriuretic peptide (ANP) are known to be involved in the regulation of LH secretion. The site of action of these peptides and the mechanisms by which they influence LHRH neurons, are largely unknown. Therefore the effects of intrapreoptic application of AII and ANP on serum LH levels of ovariectomized (ovx) and of ovx estrogen-primed rats were investigated. The peptides were applied into the PO/AH by means of push-pull cannula and in the effluent fractions GABA was measured. In the ovx estrogen-primed rat, prominent LH and prolactin surges were observed. At the time of increased LH levels preoptic GABA release was significantly reduced. At this time application of AII or ANP into the PO/AH was without effect on either LH or prolactin levels in the serum or on preoptic GABA release rates. In ovx, not steroid-primed rats intrapreoptic AII application suppressed serum LH levels significantly and this treatment had a slight stimulatory effect on preoptic GABA release rates. This effect of AII could be antagonized by prior preoptic treatment with saralasin, a specific AII receptor blocking peptide. Preoptic treatment with ANP resulted in a slight increase in serum LH levels which was accompanied by a slight, but significant reduction of preoptic GABA release rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1993

Effects of etomidate on the adrenocortical and metabolic adaptation of the neonate.

The effects of etomidate on corticosteroid synthesis were compared with those of methohexitone. We studied 40 neonates, 22 delivered by elective and 18 by emergency Caesarean section. Apgar scores, blood sugar and plasma concentrations of cortisol and etomidate were evaluated at birth and 2 and 6 h postpartum. There was no difference in Apgar scores attributable to the induction agent. The median cortisol concentrations in cord blood were small (136 nmol litre-1; range 47-478 nmol litre-1, and 259 nmol litre-1; range 58-1504 nmol litre-1 after elective and emergency sections, respectively). During the study, cortisol concentrations increased in the infants in the methohexitone groups and decreased in those in the etomidate groups; this effect was most evident 2 h after delivery (methohexitone groups 245 nmol litre-1, range 70-959 nmol litre-1; etomidate groups 121 nmol litre-1, range 56-320 nmol litre-1). There was no difference at 6 h postpartum (methohexitone groups 183 nmol litre-1, range 25-756 nmol litre-1; etomidate groups 190 nmol litre-1, range 33-628 nmol litre-1). The concentration changes during the study period differed significantly (P < 0.005) with respect to the induction agent. Blood glucose concentrations were small (mean (SD) in all 40 neonates 2 h postpartum was 2.64 (0.77) mmol litre-1), and did not differ between the groups. There were 17 cases of moderate to severe hypoglycaemia (blood glucose concentrations less than 2.5 mmol litre-1): nine in the etomidate group and eight in the methohexitone group.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Obstetrical↗

PubMed1993

Luteotrophic and luteolytic actions of ovarian peptides.

Corpora lutea of all species investigated so far, including the human, produce oxytocin and a variety of other regulatory peptides. The role of these peptides is largely unknown. The subtypes of large luteal cells are able to produce tumour necrosis factor (TNF) and at the end of the luteal phase TNF-producing macrophages invade the aged corpus luteum, indicating that this cytokine may be involved in the process of luteolysis. The present contribution reviews briefly the known functions of oxytocin and substance P in the corpus luteum and then elaborates the possible involvement of luteal and macrophage TNF during luteolysis. Oxytocin applied to intact corpus luteum stimulates the secretion of progesterone and oestradiol. The stimulation of progesterone secretion by oxytocin is due to the stimulated oestrogen production. TNF, when tested in vitro, inhibits both luteal cell progesterone and oestradiol production. The TNF-mediated inhibition of aromatase activity therefore prevents the luteotrophic effects of a variety of peptides including oxytocin. This appears to be the mechanism by which TNF induces luteolysis.

Animals↗

PubMed1993

Laterality of the gonadotrophin releasing hormone pulse generator in the rat: interaction of neurons located in both preoptic areas as a basic feature.

Though the pivotal importance of pulsatile gonadotrophin releasing hormone (GnRH) release from the hypothalamus for sufficient luteinizing hormone (LH) secretion is well recognized, the mechanisms causing GnRH pulses are still largely unknown. In the rat, the GnRH neurons are concentrated in the preoptic area, which is a bilateral structure of the anterior hypothalamus. This distribution into two distinct brain areas raises the question of whether the GnRH neurons in both preoptic areas are simultaneously or alternatively active and whether an interaction between both areas is required to generate GnRH pulses. We addressed these questions by unilateral manipulations of the activity of GnRH neurons using either electrical lesion or local infusion of gamma-aminobutyric acid (GABA), a neurotransmitter known to inhibit LH release via a hypothalamic action. Acute lesion of one preoptic area caused complete cessation of pulsatile LH release which was restored after 48 h. An acute inhibition of LH release was also observed after unilateral preoptic application of GABA. It is concluded that an interaction of both preoptic areas is mandatory for GnRH pulse generation. However, we suggest that the pacemaker function is not intrinsic to GnRH nor GABA neurons but the cross-talk between these neurons within and between both preoptic areas results in episodic GnRH release.

Animals↗

PubMed1993

Demonstration of oxytocin receptors in porcine corpora lutea: effects of the cycle stage and the distribution on small and large luteal cells.

Recent investigations have demonstrated an inhibitory effect of oxytocin (OXT) on luteal cell progesterone (P) release under in vitro conditions. This inhibitory effect was counteracted by an OXT antagonist, indicating that it was receptor-mediated. In the present investigation, we demonstrated the presence of OXT binding sites in porcine luteal tissue using a radioiodinated OXT antagonist, [1-(beta mercapto-beta,beta-cyclopentamethylene propionic acid),2-(ortho-methyl)-Tyr2-Thr4-Orn8-Tyr-NH2] vasotocin (OTA), as ligand. For membrane fractions of porcine luteal tissue, Kd values of 0.7-0.8 nM were obtained; these are comparable to those of porcine myometrial fractions, measured under the same experimental conditions. Competition studies with luteal membrane fractions yielded a Ki(OXT) of 10(-9) M. This is a dose of OXT that exerts inhibitory effects on P release under both in vitro and in vivo conditions. To evaluate putative variations of luteal OXT receptor concentrations during the estrous cycle, membrane fractions prepared from corpora lutea (CL) of the early or midluteal (Days 2-6) and late luteal phase (Days 9-11) were used. While no differences in Kd values were observed, OXT binding capacities were significantly (p < 0.05) higher in CL from the early/midluteal phase (Bmax(E/M) = 116 +/- 12 fmol/mg protein) compared to CL from the late luteal phase (Bmax(L) = 65 +/- 10 fmol/mg protein). OXT binding sites were present in both small (SLC) and large luteal cells (LLC). SLC but not LLC responded to hCG with a significant increase of OXT binding sites, whereas E2 augmented OXT receptor binding in SLC as well as in LLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Estradiol modulates the LH release response to N-methyl-D-aspartate in adult female rats: studies on hypothalamic luteinizing hormone-releasing hormone and neurotransmitter release.

We investigated the effect of ovariectomy (OVX) and subsequent estradiol benzoate (EB) treatment upon the N-methyl-D-aspartate (NMDA)-induced LH secretion in adult female rats. Furthermore, the release of LHRH, norepinephrine (NE), dopamine (DA), 5-hydroxyindoleacetic acid (5-HIAA) and gamma-aminobutyric acid (GABA) from superfused hypothalamic fragments explanted from OVX and OVX-EB rats was determined. Two weeks after OVX, animals received EB (100 mg/kg) s.c., or oil vehicle (OVX-EB or OVX groups, respectively). Two days thereafter, at 09.00 h, NMDA (15 or 30 mg/kg) was given as an i.v. bolus; blood samples were drawn before and 10 min after drug administration. In OVX rats, NMDA had no significant effect on LH levels, whereas it stimulated LH release in OVX-EB animals at both doses tested (315 and 362% from basal values, p < 0.001). For hypothalamic superfusion studies OVX and OVX-EB animals were decapitated at 09.00 h, and the mediobasal hypothalami (MBH) dissected on ice. NMDA (10(-4) M) was added to the superfusion medium for a 10 min period. Basal LHRH release (OVX: 1.41 +/- 0.18; OVX-EB: 1.59 +/- 0.28 pg/10 min/MBH) was significantly (p < 0.05) enhanced by NMDA (OVX: 2.97 +/- 0.95; OVX-EB: 2.80 +/- 0.61 pg/10 min/MBH). EB treatment had no significant effect on basal or NMDA-induced LHRH output.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Preoptic release of amino acid neurotransmitters evaluated in peripubertal and young adult female rats by push-pull perfusion.

In order to evaluate the participation of amino acid neurotransmitters (AANT) in pubertal development, we measured the preoptic release rates of glutamate (Glu), aspartate (Asp), homocysteic acid (HCA), gamma-aminobutyric acid (GABA), glycine (Gly), and taurine (Tau) in female rats aged 26, 35 and 42 days. Push-pull cannulae were implanted in the preoptic area (POA) after reinforcing the os calvarium by cementing a slightly curved 2-mm thick polyethylene plaque. Four days later, 120-min perfusion experiments (0-90 min: artificial CSF; 90-120 min: CSF containing 50 mM KCl) were performed. Amino acid concentrations were measured in 15-min fractions after derivatization with phenylisothiocyanate, using reverse-phase high-performance liquid chromatography and UV detection. Rats aged 42 days showed significantly (p < 0.01) higher preoptic Asp release rates, as compared to 26-day-old rats; Glu output increased significantly (p < 0.05) in animals aged 35 and 42 days, as compared to 26-day-old rats. No significant changes in HCA release were observed. Preoptic release rates of GABA, Gly and Tau were significantly higher in 26-day-old animals as compared to 35-day-old (GABA, p < 0.05) and 35- and 42-day-old rats (Gly, Tau, p < 0.01). Basal release of Asp, Glu, HCA, Tau and GABA, but not of Gly, was significantly stimulated (p < 0.05) by KCl in all age groups. It is suggested that in peripubertal female rats, increased preoptic Asp and Glu release rates and decreased GABA and Tau output might enhance luteinizing hormone-releasing hormone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1993

A partial blockade of catecholaminergic neurotransmission with 6-hydroxydopamine decreases mRNA level of gonadotropin releasing hormone in the male rat hypothalamus.

Central catecholamines (CA) are known to be involved in the regulation of synthesis and secretion of gonadotropin releasing hormone (GnRH) from the hypothalamus. However, no attempt has been yet made to determine whether CA affects GnRH gene expression. To this end, the effect of 6-hydroxydopamine (6-OHDA), a catecholaminergic neurotoxin, on GnRH mRNA level was examined. Hypothalamic tissues obtained from adult male rats were incubated with medium containing 6-OHDA. To ensure the effect of 6-OHDA on CA depleting action, CA levels in media and in postincubation tissues were determined. Increasing concentrations of 6-OHDA resulted in decrease in norepinephrine (NE) and dopamine (DA) contents in a dose dependent manner. Treatment with 6-OHDA (5 x 10(-4) M produced a time-dependent decrease in NE but not DA, when CA levels in media were determined at 30 min intervals during the incubation period. To determine changes in GnRH mRNA level in response to 6-OHDA treatment in vitro, for 2.5 h total cytoplasmic RNA fractions were isolated from postincubation hypothalamic tissues and used for RNA-blot hybridization with 32P-labeled GnRH riboprobe. A blockade of CA neurotransmission with 6-OHDA (5 x 10(-4) M) significantly reduced GnRH mRNA level by half over its control and internal control (actin mRNA) groups. Northern blot analysis revealed that addition of NE (1 x 10(-6) M) reversed the decreased GnRH mRNA level by 6-OHDA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Secretory granules and granins in hyperstimulated male rat gonadotropes.

Granins are acidic proteins co-localized with peptides in secretory granules of many endocrine cells. They are thought to participate in certain steps of the regulated secretory pathway. This is of particular interest in rat pituitary gonadotropes, which in most cases contain both gonadotropins (follicle-stimulating hormone, FSH and luteinizing hormone, LH) and two granins (chromogranin A, CgA and secretogranin II, Sg II). Therefore, we investigated male rat gonadotropes ultrastructurally and for the cellular and subcellular localization of gonadotropins/granins under normal conditions and after stimulation by luteinizing hormone-releasing hormone (LHRH) or castration. Typical gonadotropes of controls contained differently composed secretory granules: small granules showed immunoreactivity for LH and SgII and larger granules were immunoreactive for FSH and CgA and to a lesser extent, for LH. Stimulated gonadotropes showed hypertrophy or hyperplasia and RIA for plasma LH levels showed a 30-70-fold increase. In stimulated cells a third type of secretory granule became prominent. These "intermediate" granules had an electron-dense core immunoreactive for LH and SgII, whereas CgA labeling was confined to a less electron-dense outer region. (In stimulated gonadotropes, FSH immunoreactivity could be shown effectively only at the light microscopic level.) Intermediate granules developed from structures resembling condensing vacuoles. They began to exhibit their typical double structure as they budded off from the trans-Golgi network. It therefore appears that CgA and SgII participate in establishing two different routes of the regulated pathway in gonadotropes. Therefore, immunocytochemistry of the granins seems to be a suitable approach to investigating secretory pathways in these endocrine cells.

Animals↗

PubMed1993

Effects and interactions of prostaglandin F2 alpha, oxytocin, and cytokines on steroidogenesis of porcine luteal cells.

In the porcine corpora lutea (CL), prostaglandin F2 alpha (PGF2 alpha) and oxytocin (OXT) inhibit progesterone (P) but stimulate estradiol (E2) secretion from luteal cells kept under primary culture conditions. In vivo, both compounds are reported to have luteolytic properties when administered during the late luteal phase; in young CL, however, both substances stimulate P secretion, an effect which is E2-mediated. During the late luteal phase luteal cells appear to produce cytokines, and in addition, cytokine-producing macrophages invade the CL. We tested therefore whether cytokines, particularly tumor necrosis factor-alpha (TNF), have effects on basal or human CG-stimulated steroidogenesis. Furthermore, the interactions of cytokines with PGF2 alpha and/or OXT were investigated. TNF, and less potently interleukin (IL)-1 and IL-2 but not IL-6, inhibited basal as well as human CG-stimulated release of P and E2 in both small and large luteal cells. The inhibiting effect of PGF2 alpha and OXT on P secretion was augmented by these active cytokines. The stimulatory effect of PGF2 alpha and OXT on small and large luteal cell E2 production was completely inhibited. A profound stimulatory effect of E2 and small luteal cell P secretion was completely prevented by the cytokines, with TNF being more potent than IL-1 or -2. We conclude that the cytokines, particularly TNF, have luteolytic functions by their direct inhibiting effects on luteal cell P production. In addition, the cytokines inhibit synthesis and action of PGF2 alpha- and OXT-stimulated E2 secretion. Since E2 is a potent stimulator of luteal cell P production, this luteotropic signal is eliminated by cytokines, which add to the process of luteolysis.

Androstenedione↗

PubMed1993

In vivo measurement of rat ovarian collagenolytic activities.

Ovarian collagenases are necessary for the process of ovulation, and they are believed to be activated by the preovulatory LH surge. This information is largely based on in vitro investigations in which the balance between inhibitory and stimulatory principles involved in the activation of collagenase are largely disrupted. Therefore, we developed a simple and reliable method to measure collagenolytic activity in vivo in freely moving rats. By the use of a microdialysis system, a peptide coupled with methyl-coumarin is perfused into the bursa of the ovary. Collagenolytic enzymes cleave this peptide, and the cleaved fragments rediffuse into the microdialysis system. The effluent is collected in fractions, and the peptide-methyl-coumarin complex is cleaved, which results in liberation of fluorescent methyl-coumarin. This assay is linear over a wide range of collagenolytic activity, and other proteases, such as trypsin or plasmin, do not give any fluorescent signal. In proestrous rats, collagenolytic activity increases after the onset of the preovulatory LH surge. In animals in which the LH surge was disrupted by the surgical procedure but had a normal proestrous PRL surge, neither progesterone nor collagenolytic activity increased in the perfusate fluid. This indicates that it is only LH, not PRL, that activates follicular collagenolytic enzymes. Similar results were obtained in immature PMSG/hCG-treated animals. Using a well established zymographic assay, these results were confirmed, and it was further demonstrated that type I and type IV collagenase are active in the rat ovary.

Amino Acid Sequence↗