Avtor/Urednik     Perdan-Pirkmajer, Katja; Pirkmajer, Sergej; Černe, Katarina; Kržan, Mojca
Naslov     Molecular and kinetic characterization of histamine transport into adult rat cultured astrocytes
Tip     članek
Vir     Neurochem Int
Vol. in št.     Letnik 61, št. 3
Leto izdaje     2012
Obseg     str. 415-22
ISSN     0197-0186
Jezik     eng
Abstrakt     Astrocytes have a key role in the clearance and inactivation of histamine in the adult central nervous system, but transporters which mediate histamine uptake into astrocytes have not been fully characterised. We therefore investigated the kinetic and molecular characteristics of histamine uptake into cultured adult rat astrocytes. [3H] -histamine was taken up by astrocytes in a temperature-, time- and concentration-dependent manner and was inhibited up to 60-70% by 1 mM ouabain or by substitution of NaCl with choline chloride. Specific [3H]-histamine uptake, determined as the difference between transport at 37⁰C and 4⁰C, displayed saturation kinetics with the apparent Michaelis-Menten constant (Km) of 141 ?M and 101 ?M and the apparent maximal uptake rate (Vmax) of 22.5 pmol/min/mg protein and 17.8 pmol/min/mg protein, as estimated from the Woolf and the Eadie-Hofstee plots, respectively. Since our data suggested the presence of a carrier-operated histamine uptake system, we assessed the possible involvement of the organic cation transporters (OCT) 1, 2 and 3, which have been previously described to play a role in histamine transport in the central nervous system. Low level mRNA expression of all OCT isoforms was detected, but in contrast to rat brain cortex homogenate, where OCT3 was the most prominently expressed OCT isoform, OCT2 mRNA was the predominant OCT species in cultured astrocytes. However, OCT inhibitors corticosterone and decynium 22 (D22) had no effect or only modestly reduced [3H]-histamine uptake. Thus, our data indicate that adult rat astrocytes possess an efficient high-capacity, low-affinity carrier-operated histamine uptake system, which does not seem to involve OCTs.
Deskriptorji     ASTROCYTES
HISTAMINE
OUABAIN
KINETICS
TRITIUM
CARRIER PROTEINS
RNA, MESSENGER
CORTICOSTERONE
TEMPERATURE
TIME FACTORS
POLYMERASE CHAIN REACTION
CELLS, CULTURED
ADULT
RATS, WISTAR