Multiple endorphins in neuronal hybrid cell lines

Characterization of bradykinin-induced phosphoinositide turnover in neurohybrid NCB-20 cells

Phosphoinositide hydrolysis was studied in neurohybrid NCB-20 cells prelabeled with myo-[3H]inositol. Among nearly 20 neurotransmitters and neuromodulators examined, only bradykinin, carbachol, and histamine significantly increased the accumulation of [3H]inositol monophosphate (IP1) in the presence of lithium. The EC50 of bradykinin was 20 nM and the saturating concentration was approximately 1 microM. The bradykinin response was robust (10-fold) and was potently and selectively blocked by a bradykinin antagonist, B 4881 [D-Arg-(Hyp3, Thi, D-Phe)-bradykinin], with a Ki of 10 nM. This effect of bradykinin appeared to be additive to that mediated by activation of muscarinic cholinergic and histamine H1 receptors. The accumulation induced by bradykinin or carbachol was dependent on the presence of calcium in the incubation medium; less than twofold stimulation was observed in the absence of exogenous calcium. Bradykinin-induced [3H]IP1 accumulation required high concentration of lithium to elicit its maximal stimulation; the concentration of lithium required for half maximal effect was about 13 mM, similar to the value reported previously for carbachol-induced accumulation in the same cell line. In contrast, using related neurohybrid NG108-15 cells, bradykinin-induced [3H]IP1 accumulation was found to require much less lithium. IN the presence of lithium, bradykinin also evoked a transient increase in the production of [3H]-inositol bis- and trisphosphate. Basal and bradykinin-induced phosphoinositide breakdown was inhibited by 4 beta-phorbol 12,13-dibutyrate, but was unaffected by the biologically inactive 4 beta-phorbol. Pretreatment of cells with pertussis toxin induced only about 30% loss of the bradykinin-induced [3H]IP1 accumulation, without affecting basal activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential regulation by butyrate and dibutyryl cyclic AMP of delta-opioid, alpha 2-adrenergic, and muscarinic cholinergic receptors in NCB-20 cells

Long-term treatment of NCB-20 cells with sodium butyrate resulted in a marked increase in the specific binding of [3H]D-Ala2,D-Leu5 enkephalin. This increase was concentration and time dependent, with an EC50 of about 480 microM and a maximal effect detected after 3-day treatment. At saturating concentration of butyrate (1 mM) the increase was three- to fourfold of the untreated control. Scatchard analysis revealed that the butyrate effect was due to an increase in the density of the opioid receptor binding sites. Butyrate also induced a smaller (about twofold) increase in the density of muscarinic cholinergic receptor binding assessed by using [3H]quinuclidinyl benzilate, whereas alpha 2-adrenergic receptor binding assessed by using [3H]clonidine was not significantly affected. The butyrate-induced opioid receptor binding could be totally abolished by the presence of cycloheximide, suggesting that the butyrate effect involves synthesis of the receptor protein. Butyrate treatment did not affect basal and prostaglandin E1-stimulated cyclic AMP levels but caused a three- to fourfold decrease in the IC50 of D-Ala2,D-Leu5 enkephalin for attenuating these cyclic AMP levels and approximately 25% increase in the maximal extent of attenuation. In contrast to the butyrate effect, long-term treatment of NCB-20 cells with 1 mM dibutyryl cyclic AMP induced an 80% decrease in the opioid and alpha 2-adrenergic receptor bindings and a 57% loss of muscarinic cholinergic receptor binding. This down-regulation of muscarinic cholinergic receptor binding sites was associated with a 35% decrease of carbachol-induced phosphoinositide breakdown, whereas the receptor up-regulation induced by butyrate was found to increase the carbachol response by about threefold. The differential regulation by butyrate and dibutyryl cyclic AMP suggests that the butyrate effect is mediated by a mechanism independent of intracellular cyclic AMP. The induction by butyrate of opioid-receptors and muscarinic cholinergic receptors in NCB-20 cells may provide a useful system for studying the regulation of gene expression of these receptor proteins.

Evidence for the expression of peptides derived from three opioid precursors in NG 108CC15 hybrid cells

Five opioid peptides (immunoreactivity) derived from their respective opioid precursors were measured in neuroblastoma-glioma hybrid cells (NG 108CC15; pmol/g protein): heptapeptide (Tyr-Gly-Gly-Phe-Met-Arg-Phe), 13.0 +/- 2.6; alpha-neoendorphin, 6.6 +/- 0.8; dynorphin A, 4.4 +/- 1.5; dynorphin A 1-8, 1.3 +/- 0.29; beta-endorphin, 0.3 +/- 0.13. These peptides originate from preproenkephalin A (heptapeptide), prodynorphin (alpha-neonedorphin, dynorphin A, dynorphin A 1-8) and proopiomelanocortin (beta-endorphin). The data suggest the expression of all three known opioid precursors in a single hybrid cell line, permitting a simultaneous investigation of the processing of different opioid peptides under identical experimental conditions.

Presence of dynorphin-like immunoreactivity but not opiate binding in Walker-256 tumors

Walker-256 tumor tissue was removed from rats on day 8 of tumor growth. An acidified methanol extract of the tumor tissue was assayed for immunoreactive (ir) dynorphin-A 1-17 (DYN-17) and ir-dynorphin-A (DYN-8). Levels of ir-DYN-17 and ir-DYN-8 were nearly 4-and 8-fold higher, respectively, in tumors versus normal muscle. However, tumor homogenates did not exhibit specific 3H-naloxone binding. These results indicate that although the Walker-256 carcinosarcoma may produce opioids, it is unlikely that these ectopic substances have direct opioid actions on the tumor itself.

Light and ultrastructural characteristics of neuroblastoma glioma hybrid NG 108-15 cells

"Undifferentiated" neuroblastoma glioma hybrid NG 108-15 cells have not previously been characterized at a light and ultrastructural level despite their use in opiate receptor studies and their possession of one or more opioids. Three cell types rather than one were found. Type A is the classic round hybridoma cell. Type B is a neuron like cell and Type C is a giant cell similar to Type A cells but larger and with dense cytoplasm. Dense core vesicles, 800-1200 Ao in diameter were found as were virus particles in most Type A cells. Multivesicular bodies with clear vesicles which are interpreted as glutaraldehyde artefacts were found but no clear neurosecretory vesicles were found in any A cells--Etorphine at 10(-6) M for 48 hours and naloxone 10(-4) M were employed to product dependence and precipitated abstinence but no clear cut morphologic differences were noted between control, opiate dependent and precipitated abstinent cells.