A COMPARATIVE STUDY ON THE SYNTHESIS OF THE NATRIURETIC HORMONE DOPAMINE IN OK AND LLC-PK1CELLS

✍ Scribed by P. SOARES-DA-SILVA; M.P. SERRÃO; M.A. VIEIRA-COELHO

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 231 KB
• Volume: 20
• Category: Article
• ISSN: 1065-6995
• DOI: 10.1006/cbir.1996.0070

✦ Synopsis

Abstract

The__V__~max~values (in nmol/mg protein/15 min) for AAAD in OK cells (0.94±0.08) were found to be significantly (P<0.01) lower than those observed in LLC‐PK~1~cells (4.37±0.08). However, in both cell lines decarboxylation reaction was a saturable process with similar__K__~m~values (OK cells=1.1 mm(0.3, 1.8); LLC‐PK~1~cells=1.8 mm(1.6, 2.1)). Contrariwise to OK cells, decarboxylation ofl‐DOPA to dopamine in LLC‐PK~1~cells followed a linear (7.6±0.1 pmol/mg protein/min) non‐saturable kinetics till 120 min of incubation. The formation of dopamine from increasing concentrations ofl‐DOPA (10 to 500 μm) followed a non‐linear kinetics in both cell lines; the process ofl‐DOPA decarboxylation was saturated at low concentrations ofl‐DOPA with an apparent__K__~m~value of 11 μm(0.2, 22.6) in OK cells and 27.4 μm(11.1, 43.7) in LLC‐PK~1~cells. The formation of dopamine in LLC‐PK~1~cells (V~max~=2097±113 pmol/mg protein/6 min) was 13.7‐fold that occurred in OK cells (V~max~=153±10 pmol/mg protein/6 min). In conclusion, LLC‐PK~1~cells appear to be endowed with a greater ability to form dopamine from exogenousl‐DOPA when compared to OK cells.