Release of immunoreactive angiotensin II from neuronal cultures: adrenergic influences

The effects of adrenergic drugs on the release of immunoreactive angiotensin II (ANG II-ir) from brain cells in culture were examined. In neuronal cultures, basal release of Ang II-ir was 43.65 +/- 7.44 pg/5-min incubation period (n = 14 experiments; 52 individual determinations), and in astrocytic glial cultures, it was 21.76 +/- 5.7 pg (n = 8 experiments; 24 individual determinations) when cells were exposed to buffer alone. Incubation of neuronal cultures with the alpha 2-adrenergic antagonist yohimbine (0.1-50 microM, 5 min) caused concentration-dependent increases in ANG II-ir release above basal levels. Analysis of the released material by high-pressure liquid chromatography revealed that authentic ANG II was present. No increase in the release of ANG II-ir was seen from glial cells. Experiments using neuronal cultures revealed that the yohimbine-induced release of ANG II-ir may be secondary to increased norepinephrine (NE) release. Incubation of neuronal cultures with NE (10 nM-50 microM) caused concentration-dependent increases in the release of ANG II-ir. This effect of NE was not inhibited by the alpha 1-adrenergic blocker prazosin. However, a weaker release of ANG II-ir from neuronal cultures was stimulated by the beta-adrenergic agonist isoproterenol at 100 microM. These data show that ANG II-ir can be released from neuronal but not glial cell cultures by adrenergic receptor-mediated mechanisms.