Dopamine release via protein kinase C activation in the fish retina.
Calcium-dependent phospholipid-sensitive protein kinase [protein kinase C (PKC)] was partially purified from the carp (Cyprinus carpio) retina through DE 52 ion exchange and Cellulofine gel filtration chromatography. The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) activated PKC in the nanomolar range. A major 38-kDa protein in the retinal supernatants (105,000 g) was phosphorylated in vitro by PKC during a short period (3 min). Other phosphoproteins also appeared during a further prolonged period (greater than 15 min). Rod-bipolar and dopamine (DA) interplexiform cells in the fish retina were immunoreactive to a monoclonal antibody to PKC (alpha/beta-subtype). The PKC antibody recognized a 78-kDa native PKC enzyme by means of an immunoblotting method. Subsequently, the effects of two kinds of PKC activators were investigated on [3H]DA release from retinal cell fractions containing DA cells that had been preloaded with [3H]DA. A phorbol ester (TPA) induced a calcium- and dose-dependent [3H]DA release during a short period (2 min), with the minimal effective dose being approximately 1 nM. Other phorbols having no tumor-promoting activity, such as 4 beta-phorbol and 4 alpha-phorbol 12,13-didecanoate, were ineffective on [3H]DA release. A synthetic diacylglycerol [1-oleoyl-2-acetylglycerol (OAG)], which is an endogenous PKC activator, was also able to induce a significant release of [3H]DA. Furthermore, TPA was found to release endogenous DA from isolated fish retina by a highly sensitive HPLC with electrochemical detection method. The OAG- or TPA-induced [3H]DA or DA release was completely blocked by inhibitors of PKC, such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) and staurosporine.(ABSTRACT TRUNCATED AT 250 WORDS)
Kato
S
S
Department of Neurophysiology, University of Kanazawa School of Medicine, Ishikawa, Japan.
Ishita
S
S
Mawatari
K
K
Matsukawa
T
T
Negishi
K
K
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002347:Carps; D002851:Chromatography, High Pressure Liquid; D004075:Diglycerides / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D004563:Electrochemistry / Q000379:methods; D004789:Enzyme Activation; D007150:Immunohistochemistry; D011493:Protein Kinase C / Q000378:metabolism*; D012160:Retina / Q000201:enzymology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014316:Tritium
D000596:Amino Acids; D004075:Diglycerides; D014316:Tritium; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D004298:Dopamine