Uptake, metabolism, and release of [3H]-histamine by glial cells in primary cultures of chicken cerebral hemispheres

✍ Scribed by Dr. Zsuzsanna Huszti; Ágnes Rimanóczy; Anna Juhász; Kálmán Magyar

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 889 KB
• Volume: 3
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.440030303

✦ Synopsis

Labelled histamine was taken up into cultured glial cells of chick embryonic brain by a system with high affinity for histamine and diffusion. The active uptake, occurring at low concentrations of the amine, was Na+ dependent and gave an apparent K, of 0.24 pM and a V, , , of 0.31 pmol x mg protein -' x min-l. The uptake was completely blocked by desmethylimipramine (Ki =2.5 pM) and partially by the histamine agonists and histamine-N-methyltransferase blockers 4-methylhistamine and 2-methylhistamine (I3,, values obtained were 2 pM and 5 pM). Other psychoactive drugs were either ineffective (imipramine) or they showed moderate inhibitory effects (amitryptyline and cocaine). Ouabain (100 pM) inhibited uptake by -50%. Diffusion occurred at high concentrations of the amine, was insensitive to extracellular Na+, and was proportional to histamine concentration up to 1 mM.

[3H]-Histamine, taken up into the cells, was metabolized and/or released. The spontaneous efflux of the radioactivity measured after 10 min of exposure to [3H]-histamine (when most of it was still unmetabolized), was moderately Ca++ dependent, accelerated by both reduced concentrations of extracellular Na+ and enhanced concentrations of K+ and inhibited by desmethylimipramine. After prolonged (60 min) incubation, histamine metabolites detected in the cells presented 78% of the chromatogram radioactivity and consisted of W-methylhistamine and W-methylimidazole acetic acid.

These results indicate that at low nM concentrations, histamine is taken up and metabolized by (and released from) glial cells by an Na+-dependent system, and the intracellular metabolism seems to serve an increased uptake of the amine.