No abstract

In the insulin-secreting beta cell line Rin m 5F, galanin, a newly discovered ubiquitous neuropeptide, inhibited, by 50%, the stimulation of insulin release induced by gastric inhibitory polypeptide (GIP) or forskolin, i.e. two cAMP-generating effectors. In contrast, it failed to decrease the stimulation of insulin release elicited by either the Ca2+-mobilizing agent, carbamoylcholine, or by dibutyryl-cAMP. Concomitantly, galanin inhibited the GIP- and forskolin-stimulated cAMP production. Furthermore, adenylate cyclase in membranes from Rin m 5F cells was highly sensitive to galanin, which exerted a marked inhibitory effect on the forskolin-stimulated enzyme activity. All these galanin effects were observed at low physiological doses, in the nanomolar range. Overnight treatment of the Rin m 5F cells with pertussis toxin completely abolished the inhibitory effect of galanin on insulin release, cAMP production and adenylate cyclase activity. Moreover, pertussis toxin specifically ADP-ribosylated a 39-kDa protein present in membranes from those cells. Taken together, these data show that the galanin inhibition of insulin release most likely occurs through the inhibition of adenylate cyclase, involving a petussis-toxin-sensitive inhibitory GTP-binding regulatory protein.

No abstract

Neuroretina (NR) is an evagination of the central nervous system (CNS) which is composed of photoreceptors, glial (Müller) cells and horizontal, bipolar, amacrine and ganglion neuronal cells. We describe here the usefulness of Rous sarcoma virus (RSV) in the establishment of a neuronal clone from quail embryo neuroretina. When primary cultures of chick and quail embryo neuroretina cells are transformed by RSV, neuronal markers such as ribbon synapses, choline acetyltransferase (CAT) and glutamic acid decarboxylase (GAD) specific activity are present. These RSV-transformed primary cultures can be established into permanent cell lines from which neuronal clones have been isolated. One of them, clone QNR/D, can generate tetrodotoxin(TTX)-inhibitable action potentials on electrical stimulation, has a high GAD activity and binds monoclonal antibodies raised against chick embryo neuroretina. The presence of these neuronal markers suggests that the QNR/D clone is derived from cells of the amacrine or ganglionic lineage. This is the first time that a neuronal cell clone of defined origin has been obtained from the CNS. The neuronal markers of the QNR/D clone are expressed at both the permissive and the non-permissive temperatures for transformation.