Plant Regeneration from Protoplasts of Ligusticurn wallichii Franch

The hypocotyls of the embryoid derived plantlets of Ligusticum wallichii Franch were used for protoplast preparation. Protoplasts were obtained with the enzyme mixture containing 1.5% Onozuka R-10, 0.3% Macerozyme R-10, 0.5% Snailase, 5 mmol/l CaCl2, 1 mmol/l KH2PO4, 0.6 mol/l manitol, at pH 5.6–5.8 and 27℃. Protoplasts were cultured in a modified MS liquid medium containing 1 mg/l 2,4-D + 0.5 mg/l 6- BA. The first divisions were found after twelve days, and the dividing cells formed cell colonies of 0.5–1 mm after about fourty days. When they were transferred to MS agar medium (with half quantity of macronutrients) supplemented with 2,4-D (0.5mg/l) and 6-BA(0.5mg/l), they grew into calli. At last, on the medium without any phytohormones, the growing calli differentiated embryoids which developed into plantlets with many green leaves and roots.     

Production,maintenance and plant regeneration from cell suspension cultures of Stevia rebaudiana (Bert.) Bertoni

A method is described for producing and maintaining Stevia rebaudiana suspensions and regeneration of plants from calli derived from cell suspensions. Suspension cultures composed of isolated cells (ca. 10%) and cellular aggregates (5–100 cells) were obtained in 20–30 days by using friable callus as the initial inoculum in liquid medi with BA (0.5 mg/l)+2,4-D (1.0 mg/l), and periodic filtering (100–500 m sieves) with 6–7 days interval between subcultures. Cultures derived from actively growing calli are mainly diploid (2n=22) whereas those derived from senescent calli showed a wide variation in chromosome number (55–200). Stock cell suspensions which had been maintained for 3 years were plated on basal LS agar medium with BA (0.5 mg/l)+2,4D (0.5 mg/l) to form callus. Calli originating from predominantly 2n cell suspensions when transferred to medium with K (2.0 mg/l)+NAA (0.02 mg/l) were able to form buds. Shoot elongation and further rooting of isolated shoots was better on LS medium devoid of growth regulators. Variation in rooting capacity, plant vigour, morphological characters and chromosome number was found amongst regenerated plants.Abbreviations BA Benzylaminopurine - 2,4-D 2,4 - Dichlorophenoxyacetic acid - GA₃ Gibberellic acid - IAA Indoleacetic acid - IBA Indolebutyric acid - K Kinetin - LS Linsmaier & Skoog     

Effects of hormones (calcitonin, GIP) and pharmacological antagonists (ranitidine and famotidine) on isolated rat parietal cells

The rationale for the present study was to compare calcitonin and gastric inhibitory polypeptide (GIP) versus two histamine H2 receptor antagonists with respect to their potency of inhibiting parietal cell functions. Adenylate cyclase activity and acid production ([14C]aminopyrine uptake) of isolated rat parietal cells were stimulated by histamine. At 10(-7) and 10(-6) mol/l, calcitonin and GIP reduced the response to histamine by 10-20% following noncompetitive kinetics. Ranitidine and famotidine (MK 208) inhibited the response to histamine by about 50% at 10(-7)-10(-6) mol/l, and at 10(-5) mol/l abolished the histamine effect. On a molar basis famotidine turned out to be 6 times more potent than ranitidine. Both antagonists revealed competitive kinetics. Our data suggest direct inhibition of the parietal cells by the tested compounds which were shown to interfere at the adenylate cyclase cAMP system or at the histamine H2 receptor. However, compared to the histamine H2 receptor antagonists, hormonal inhibition is less pronounced and mediated by a different mechanism.     

Inhibition of rat synaptic membrane Na⁺/K⁺-ATPase and ecto-nucleoside triphosphate diphosphohydrolases by 12-tungstosilicic and 12-tungstophosphoric acid

The in vitro influence of Keggin structure polyoxotungstates, 12-tungstosilicic acid, H(4)SiW(12)O(40) (WSiA) and 12-tungstophosphoric acid, H(3)PW(12)O(40) (WPA), and monomer Na(2)WO(4) × 2H(2)O on rat synaptic plasma membrane (SPM) Na(+)/K(+)-ATPase and E-NTPDase activity was studied, whereas the commercial porcine cerebral cortex Na(+)/K(+)-ATPase served as a reference. Dose-dependent Na(+)/K(+)-ATPase inhibition was obtained for all investigated compounds. Calculated IC(50) (10 min) values, in mol/l, for SPM/commercial Na(+)/K(+)-ATPase, were: 3.4 × 10(-6)/4.3 × 10(-6), 2.9 × 10(-6)/3.1 × 10(-6) and 1.3 × 10(-3)/1.5 × 10(-3) for WSiA, WPA and Na(2)WO(4) × 2H(2)O, respectively. In the case of E-NTPDase, increasing concentrations of WSiA and WPA induced its activity reduction, while Na(2)WO(4) × 2H(2)O did not noticeably affect the enzyme activity at all investigated concentrations (up to 1 × 10(-3)mol/l). IC(50) (10 min) values, obtained from the inhibition curves, were (in mol/l): 4.1 × 10(-6) for WSiA and 1.6 × 10(-6) for WPA. Monolacunary Keggin anion was found as the main active molecular species present under physiological conditions (in the enzyme assays, pH 7.4), for the both polyoxotungstates solutions (1 mmol/l), using Fourier transform infrared (FT-IR) and micro-Raman spectroscopy. Additionally, commercial porcine cerebral cortex Na(+)/K(+)-ATPase was exposed to the mixture of Na(2)WO(4) × 2H(2)O and WSiA at different concentrations. Additive inhibition effect was achieved for lower concentrations of Na(2)WO(4) × 2H(2)O/WSiA (≤ 1 × 10(-3)/4 × 10(-6) mol/l), while antagonistic effect was obtained for all higher concentrations of the inhibitors.     

Organogenesis of Leaf Explant of Populus davidiana(bolleana Loucne Hybrid and Effect of Growth Regulators on Organogenesis

This report describe the organogenesis of Populus davidiana × P. bolleana Loucne hybrid leaf explant from plantlet in vitro and the effects of different factors on its organogenesis. It was found that shoot induction of lower leaf segments with petiole was easier than those of the middle and top segments. When leaf explants were in- cubated on a MS midium with eytokinin (zeatin l×l0-6 M–2×10-6 M or benzyladenine 2 × 10-6 M) and auxin (IAA 4 × 10-8 M–1 × 10-6 M or NAA, NAAoxy 4 × 10-8 M–4 × 10-7 M), the frequeney of shoot differentiation would be 70%–100%. Kinetin had no activity on shoot formation and 2, 4-D showed serious inhibition. ABA, GA3, and Ethrel all prevented shoot production. Since higher frequency of shoot differentiation could be obtained, a lot of shoots were produced cneach leaf explant and shoots could be proliferated by axillary buds, so this system could be used for rapid propagation.     

Transport of L-carnitine induced by prednisolone in an established cell line (CCL 27). A possible explanation of the therapeutic effect of glucocorticoids in muscular carnitine deficiency syndrome.

Prednisolone (10(-8)--10(-5) mol/l) in the growth medium for 24 h increased the rate of uptake of L-[3H]carnitine in an established cell line (CCL 27) to 164 +/- 6% (mean +/-S.E.) of the rate observed in untreated cells. At the same time the intracellular content of free L-carnitine increased about 20%. The simultaneous addition of prednisolone (10(-6) mol/l for 24 h) and L-carnitine (10(-4) mol/l for 96 h) to the growth medium increased the rate of uptake to 225 +/- 8% (mean +/-S.E.) of that in untreated cells. The increase seemed to be mediated through an increase in number of carriers, as judged by the increase in V of the transport process with unchanged Km. Phosphodiesterase I, an enzyme mainly localized in the plasma membrane, increased its activity about 3.5 times when cells were stimulated with prednisolone. Thus, it seems that the increase in the rate of uptake of L-carnitine mediated by glucocorticoids, is part of a more general effect on the plasma membrane. The observations offer an explanation to the observed clinical improvement in patients with muscular carnitine deficiency treated with glucocorticoids and/or L-carnitine.     

Plants Regenerated from Mesophyll Protoplasts of Cottonwood New Clone

Poplar NL-80106 (Populus deltoides×P, simonii) mesophyll protoplasts were isolated from leaves of 30 days-old sterile shoot, with 4 × 107/g fr. wt of protoplast yield after purification. The protoplasts were cultured in KM8p and MS liquid media containing 2 mg/L 2, 4-D, 0. 5 mg/L NAA and 0.5 mg/L KT. Higher plating density and lower osmatic pressure (0.45 mol/L) were proved to be favourable to division of protoplast-derived cells. The first division initiated 5 days after culture, and the division frequency reached 4.5 % on the 10th day. A number'of cell colonies and microcalli was formed in 12 weeks. Using organic nitrates and glucose in protoplast culture medium was beneficial to increase division frequency and plating efficiency. The calli were allowed to grow to 4--6 mm in height with red colour and compact structure on the gelrite-sohdified NLZ1 proliferation medium in 3 weeks and were transferred onto NLF differentiation medium where the frequency of shoot formation could reach 100%. The 3 cm high shoots were then cut off from the callus and rooted on 1/2 MS medium.     

Some characteristics of human adrenal microsomal 21-hydroxylase activity

The following general characteristics of 21-hydroxylase activity were determined using pooled microsomes obtained from three glands. Enzyme activity exhibited a broad pH dependence, being optimal between pH 7.4-pH 7.8, and was maximal with NADPH in the range 2 to 4.75 X 10(-4)mol/l. No microsomal 21-hydroxylase activity was detected in the absence of NADPH or substrate and when heat denatured microsomes were employed. Enzyme activity was depressed by greater than 75% in the presence of 100% oxygen or nitrogen. In a second set of experiments, microsomal fractions were prepared individually from 7 glands. In the presence of 17 alpha-hydroxy progesterone (2.0 X 10(-7) and 2.0 X 10(-6)mol/l) product formation was linear with time for up to 90 s when the microsomal protein concentration was 5, 10 and 20 micrograms/ml. Between 5 and 30% of the substrate was converted during the first 60 s. In 5/7 of the glands the addition of the autologous cytosol (20 micrograms protein/ml) was without effect, and enzyme activity (using a 60 s reaction and either 2.0 X 10(-7) or 2 X 10(-6)mol/l 17 alpha-hydroxy progesterone was directly proportional to the microsomal protein concentration (range 0-20 micrograms/ml). With the other 2 adrenals 21-hydroxylation was not proportional to the same range of microsomal protein concentrations, although it became so upon the addition of cytosol, which significantly augmented activity. There was considerable variation in enzyme activity between glands from different individuals (Vmax ranging from 2.6 to 16.6 X 10(-9) mol/min/mg protein) and in the apparent Km's (from 0.22 to 1.1 X 10(-6)mol/l). In the two preparations sensitive to cytosol, the Vmax increased 2-fold, and the Km was 3 times lower. Cytosol was without effect upon the kinetic characteristics of the other 5 microsomal preparations. Ascorbic acid (1 X 10(-3) mol/l) depressed enzyme activity by 25-43% whereas oxidised and reduced glutathione (1 X 10(-3) mol/l) showed a slight and variable effect upon 21-hydroxylation.     

Evaluation of Methods for Reestablishment of L-Cell Suspension Cultures Directly from Liquid Nitrogen Stored Stocks

Methods were developed and evaluated for the preservation of tissue cells grown in suspension culture and the reestablishment of suspension cultures directly from inoculum stored at -175 C. The factors investigated were processing pH, temperature of processing, freezing medium, and method of inoculation of the starter suspension cultures from the frozen stock (-175 C). Three parameters, cell viability, cell size, and growth potential in suspension culture after freezing, were used to evaluate the various factors. The results indicate that cells processed at 4 C, frozen at 1 C per min to -50 C in a medium containing 5% dimethyl sulfoxide plus 10% bovine serum at concentrations of 2 x 10(7) to 4 x 10(7) cells/ml, and stored at -175 C will reestablish suspension cultures directly from frozen seed. A 1-ml amount of frozen stock inoculated into 99 ml of medium routinely produced 2 x 10(6) to 3 x 10(6) viable cells/ml (2 x 10(8) to 3 x 10(8) total cells) in suspension culture in 4 to 5 days. Inoculum preserved by this procedure grew equally well in either serum-free or serum-containing growth medium.     

Production and secretion of two vasoactive peptides, adrenomedullin and endothelin-1, by cultured human adrenocortical carcinoma cells

The production and secretion of peptides by adrenocortical tumors have not been well studied. We therefore studied the production and secretion of two vasoactive peptides, adrenomedullin and endothelin-1 in SW-13 human adrenocortical carcinoma cells by radioimmunoassay and Northern blot analysis. Both immunoreactive-adrenomedullin and immunoreactive-endothelin were detected in the culture medium of SW-13 cells (27.7 +/- 1.6 fmol/10 (5) cells/24 h and 11.0 +/- 0.8 fmol/10 (5) cells/24 h, respectively, mean +/- SEM, n = 6). Northern blot analysis showed the expression of adrenomedullin mRNA and endothelin-1 mRNA in SW-13 cells. On the other hand, no significant amount of calcitonin gene-related peptide, corticotropin-releasing hormone, neuropeptide Y, or urocortin was secreted by SW-13 cells. Treatment with ACTH (10(-9)-10(-7) mol/l), angiotensin II (10(-9)-10(-7) mol/l), or dexamethasone (10(-8)-10(-6) mol/l) for 24 h had no significant effects on immunoreactive-adrenomedullin levels and immunoreactive-endothelin levels in the culture medium of SW-13. Treatment with tumor necrosis factor (TNF)-alpha (20 ng/ml) increased significantly both immunoreactive-adrenomedullin levels and immunoreactive-endothelin levels in the culture medium. Interferon-gamma (100 U/ml) increased the immunoreactive-endothelin levels, but not immunoreactive-adrenomedullin levels, whereas interleukin-1 (IL-1)beta (10 ng/ml) increased immunoreactive-adrenomedullin levels, but not immunoreactive-endothelin levels. These findings indicate that SW-13 human adrenocortical carcinoma cells produce and secrete two vasoactive peptides, adrenomedullin, and endothelin-1 and that the secretion of these two peptides is modulated differently by cytokines.     

杂色云芝产漆酶的发酵条件研究*

本文对杂色云芝（Coriolus versicolor）产漆酶的发酵条件作了研究。结果表明摇瓶实验产漆酶（Laccase）的最佳培养基成分为：可溶性淀粉 2g/L, NH4Cl 24mmol/L, 微量元素混合液 7ml/L, pH3.0柠檬酸—Na2HPO4缓冲溶液 0.01mol/L, KH2PO4 1.4×10-2 mol/L, MgSO4·7H2O 2.03×10-3mol/L, CaCl2·2H2O 6.8×10-4 mol/L, VB1 2.97×10-6 mol/L, 吐温80 4.0g/L, 愈创木酚0.01mmol/L, CuSO4 ·5H2O 0.005mmol/L,最佳发酵条件为培养基初始pH3.0, 菌体生长6d,培养基装量为250ml三角瓶中25ml培养液,25℃条件下振荡培养(150r/min)9d。     

High frequency plant regeneration of Cymbopogon martinii (Roxb.) Wats by somatic embryogenesis and organogenesis

Embryogenic callus cultures were obtained upon repeated sub-culture of non-embryogenic callus from nodal segments of Cymbopogon martinii (Roxb.) Wats. Murashige and Skoog's medium supplemented with 1mg/l 2,4-dichlorophenoxyacetic acid and 0.5 mg/l kinetin and Linsmaier and Skoog's medium supplemented with 2mg/l 2,4-dichlorophenoxyacetic acid and 0.4 mg/l kinetin were used as maintenance media for non-embryogenic and embryogenic cultures, respectively. Plant regeneration occurred through organogenesis in MS basal media containing 2 mg/l kinetin, 1 mg/l 6-benzylaminopurine, 0.2 mg/l biotin, 0.2 mg/l Ca-pantothonate and 0.1 mg/l napthalene acetic acid. Embryogenesis was induced in LS medium supplemented with 1 mg/l kinetin, 0.5 mg/l 6-benzylaminopurine and 0.1 mg/l 3-indole acetic acid. Plant regeneration at high frequency was recorded both through organogenesis and embryogenesis in different passages of long term callus cultures.Abbreviation MS Murashige and Skoog medium - LS Linsmair and Skoog medium - BAP 6-benzylaminopurine - kin kinetin - 2,4-D 2,4-Dichlorophenoxyacetic acid - IAA Indole-3-acetic acid - CH Casein hydrolysate - CaP calcium pantothonate - NAA napthalene acetic acid     

Control of sulfatase and sulfotransferase activities by medrogestone in the hormone-dependent MCF-7 and T-47D human breast cancer cell lines.

In the present study, we explored the effect of the progestin medrogestone on the sulfatase and sulfotransferase activities in the hormone-dependent MCF-7 and T-47D human breast cancer cell lines. After 24 h incubation at 37 degrees C of physiological concentrations of estrone sulfate ([3H]-E1S: 5x10(-9) mol/l), it was observed that this estrogen was converted in a great proportion to E2 in both cell lines. Medrogestone significantly inhibits this transformation, at all the concentrations tested (5x10(-8) to 5x10(-5) mol/l), in both cell lines. The IC50 values were 1.93 micromol/l and 0.21 micromol/l in MCF-7 and T-47D cells, respectively. In another series of studies, after 24 h incubation at 37 degrees C of physiological concentrations of estrone ([3H]-E1: 5x10(-9) mol/l), the sulfotransferase activity was detectable in both cell lines. Estrogen sulfates (ES) are found exclusively in the culture medium, which suggests that as soon as they are formed they are excreted into the medium. Medrogestone has a biphasic effect on sulfotransferase activity in both cell lines. At low doses: 5x10(-8) and 5x10(-7) mol/l, this compound stimulates the enzyme by +73.5 and 52.7%, respectively, in MCF-7, and by 84.5 and 62.6% in T-47D cells. At high concentrations: 5x10(-6) and 5x10(-5) mol/l, medrogestone has no effect on MCF-7 cells, but inhibits the sulfotransferase activity in T-47D cells by -31.4% at 5x10(-5) mol/l. In conclusion, the inhibitory effect provoked by medrogestone on the enzyme involved in the biosynthesis of E2 (sulfatase pathway) in estrogen-dependent breast cancer, as well as the stimulatory effect on the formation of the inactive ES, support a probable anti-proliferative effect of this progestin in breast tissue. Clinical applications of these findings can open new therapeutic possibilities for this disease.     

Isolation,Culture and Callus Formation of lpomoea batatas Protoplasts

Numerous viable protoplasts from stem callus cells of Ipomoea batatas tissue culture have been isolated by enzyme treatment involving cellulase EA3 867 (2.0%), CaC12·2H2O (20 mM) and mineral constituent of medium A at pH5.4 in 0.8 M mannitol in 5 hours at 25±1℃. The protoplasts were cultured at a density of 1-2 × 105/ml in solid agar medium E supplemented with 2, 4-D (0.1mg/l) and kinetin (0.1 mg/l), or NAA (0.3 mg/l) and kinetin (0.1 mg/l) in petri dishes, and placed in a controlled growth cabinet maintained at 27 ℃, and illuminated with floureseent light. They regenerated new cell wails after 7 days of culture. The first cell division was observed after 10 days. Ceil division continued thereafter, and after 40 days of culture small white calli (size about 0.2–0.3 mm) were visible in the petri dishes small calli were inoculated in the same nutrients as the protoplasts culture media, but without mannitol. They developed into large calli.     

Plant regeneration from protoplasts of Japanese lawngrass

Embryogenic callus of Japanese lawngrass (Zoysia japonica Steud.) was induced from sterile mature seeds on LS medium with 5 mg / l of 2,4-D. Embryogenic callus selected visually under microscope was proliferated in liquid N6 medium with amino acids (N6-AA medium). Protoplasts were isolated from suspension cells by the treatment of enzyme mixture containing pectolyase Y-23 and cultured in K8p medium with 2 mg / l of 2,4-D at the density of 10⁶ / ml. Plants were regenerated by transferring the protoplasts derived callus to MS medium and incubating at 28 °C under light for two months. Plantlets were successfully transplanted in the soil.Abbreviations 2,4-D 2,4-dichrolophenoxyacetic acid - MES 2-(N-Morpholino) ethanesulfonic acid     

Additive effect of oestradiol-17 beta and serum on synthesis of deoxyribonucleic acid in guinea-pig endometrial cells in culture.

Normal guinea-pig endometrial cells, grown in primary culture, were made quiescent by serum depletion. Quiescent cells cultured in the control medium (containing 1% fetal calf serum treated with dextran-coated charcoal, DCC-FCS) showed a steady and weak rate of [3H]thymidine incorporation, but the addition of 15% fetal calf serum (FCS) or 10% DCC-FCS to the control medium induced a significant increase of DNA synthesis, demonstrating the responsiveness of the quiescent cells to stimulation. A lower but significant increase in [3H]thymidine incorporation was elicited by epidermal growth factor (EGF, 100 ng/ml) or insulin (10 micrograms/ml) added to the basal medium. Oestradiol-17 beta added to the control medium at concentrations ranging from 10(-10) to 10(-5) mol/l not only failed to increase but even inhibited [3H]thymidine incorporation at the highest concentrations tested. An additive effect was noticed when quiescent cells were incubated with oestradiol-17 beta (10(-9) mol/l) in the presence of 10% DCC-FCS, but no synergistic effect occurred when 2 x 10(-9) mol oestradiol-17 beta/l was combined with either EGF (100 ng/ml) or insulin (10 micrograms/ml). Oestradiol-17 beta appears unable alone to stimulate DNA synthesis in normal endometrial cells, but requires factor(s) present in fetal calf serum.     

Release and crystallization of berberine in the liquid medium of Thalictrum minus cell suspension cultures

Cell suspension cultures of Thalictrum minus L. var. hypoleucum Miq. were found to produce a large amount of berberine (400–800 mg/l) when 5–10 M 6-benzyladenine was added to Linsmaier and Skoog's medium containing 100 M 1-naphthaleneacetic acid. Most of the berberine produced was released continuously from the cells into the liquid medium, and an excess of berberine crystallized as its nitrate in the medium. When the cells were cultured in a modified LS medium containing 20 mM KNO₃ and 40 mM NH₄Cl in place of 20.6 mM NH₄NO₃ as nitrogen source, most of the alkaloid crystallized to form berberine chloride instead of nitrate. Minor alkaloids, thalifendine and magnoflorine, were also isolated from the medium and identified.Abbreviations LS Linsmaier and Skoog (1965) - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - BA 6-benzyladenine     

The effect of CdCl2 on the respiration of rat small intestine mucosa

Process of oxygen consumption of rat small intestine have already been studied at the level of whole intestinal wall or mucosa only by means of manometric or polarographic methods. The influence of cadmium on mucosal respiration of three sections of rat small intestine was determined because of its toxicological importance. Oxygen consumption was measured polarographically with Clark electrode at 38 degrees C in Krebs Ringer phosphate medium with 0.011 mol/l glucose. Control as well as cadmium affected respiration values were measured one after the other on the same mucosa. High cadmium concentration (applied as CdCl2) that is 2.2 and 1.4 . 10(-2) mol/l significantly inhibited the respiration in duodenum, jejunum and ileum. Observed inhibition of 80 and 50% on the average approximately for these two concentrations was related (similarly as following effects) to 100% value of control respiration. Concentrations 7.8 and 4.5. 10(-3) mol/l caused mostly lower inhibition of oxygen consumption (with the exception of significant 53% inhibition of jejunal respiration for 7.8. 10(-3) mol/l CdCl2). Low concentrations 10(-4) - 10(-6) mol/l CdCl2 had either no effect or stimulated oxygen uptake in intestinal mucosa. In older rats (weight 300-350 g) the respiration of duodenal and jejunal mucosa was inhibited with cadmium chloride concentration of 10(-6) mol/l.     

Lipolysis induced by alloxan in rat adipocytes is not inhibited by insulin.

Isolated rat adipocytes were incubated with adrenaline, adrenaline plus insulin, alloxan or alloxan plus insulin. Glycerol release was taken as a measure of lipolysis. It was observed that alloxan in the concentration of 3, 10 and 20 mmol/l intensifies lipolysis in adipocytes in the absence of adrenaline. Insulin (10(-6) mol/l) treatment of cells did not inhibit lipolysis caused by this compound, but significantly restricted lipolysis induced by adrenaline (10(-6) mol/l). It was also shown that alloxan in the concentration of 3 and 10 mmol/l intensified lipolysis stimulated by adrenaline (10(-6) mol/l). Addition of 20 mmol/l of alloxan strongly inhibited glycerol release in the presence of adrenaline. The results presented here clearly indicate that the action of alloxan concerns cells of the white adipose tissue.     

Naturally occurring opioid peptides modulate H+-production by isolated rat parietal cells

The rationale for the present study was to determine the effects of naturally occurring opioid peptides on H+-production by isolated rat parietal cells as indirectly measured by [14C]-aminopyrine uptake. In crude preparations (18 to 25% parietal cells) and in enriched (80 to 90%) parietal cell fractions stimulation by submaximal histamine- or dibutyryl cAMP-concentrations (10(-6)-10(-4) mol/l) was augmented by 20-30% in the presence of methionine-enkephalin (Met-Enk) and Met-Enk Arg6Phe7 (10(-7) to 10(-5) mol/l). This augmentation was blocked by the opiate receptor antagonist (-)naloxone (10(-6) mol/l) suggesting specificity of the action of Met-Enk and Met-Enk Arg6Phe7. At 10(-6) mol/l (-)naloxone did not exert nonspecific toxic effects. Yet, even in the absence of exogenous opioids, histamine-induced H+-production was inhibited by 3 X 10(-5) or 10(-4) mol/l (-)naloxone. Since similar inhibition occurred with (+)naloxone, an inactive stereoisomer which does not interact with opiate receptors, effects of (-)naloxone at concentrations above 10(-5) mol/l must be considered nonspecific. We conclude that Met-Enk and Met-Enk Arg6Phe7 have no effect on basal, but augment stimulated H+-production by a direct effect on the parietal cells. At nontoxic concentrations (-)naloxone antagonizes this augmentation indicating that it is mediated by specific opiate receptors on the parietal cells.