Role of excitatory amino acids on somatostatin production in the central nervous system.

since dibutyryl cyclic A M P also stimulates cell growth. T h e mcchanism is unknown; however. other workers. e.g. Rozengurt e/ ( I / . (261 reported that a sustained increase in cellular cyclic A M P acts as ii mitogenic signal for Swiss 3T3 cells. There is also a report 1271 that the catalytic subunit of cyclic A MP-dependent protein kinase may be involved in regulation o f the proto-oncogene, c-fos. From this work. it seems that p-agonists have two actions: in the short-term they stimulate rcnin release. probably through increased rate o f exocytosis o r rcnin gene expression: longer-term administration o f isoprenaline (or dibutyryl cyclic A M P ) also led t o an increased number o f renin-secreting cells and consequently a sustained and long-term increase in renin release. This finding could be applicable t o other mammalian hormones, namely agonists effective in the short-term may have a dual role as growth factors on the hormone-secreting target cell. allowing a sustained hormone response t o increased demand. However. in conclusion. it is as yet not known whether the growth-promoting cffccts o f B-agonists have clinical relevance in ncphroblastoma.