caa a22 4500 477118801 CHVBK 20180405111630.0 cr unu---uuuuu 170330e19960301xx s 000 0 eng 10.1007/BF00250992 doi (NATIONALLICENCE)springer-10.1007/BF00250992 Pinocytosis in 2,5-di- tert -butylhydroquinone-stimulated hepatocytes and evaluation of its role in Ca2+ inflow [Elektronische Daten] [Kekulu Fernando, Greg Barritt] In order to evaluate the contribution of pinocytosis to basal (no agonist) and lanthanide-insensitive store-activated Ca2+ inflow in freshly-isolated rat hepatocytes, the uptake of extracellular fluid by pinocytosis was measured at 20°C and used to predict the amount of extracellular Ca2+ taken up by pinocytosis. This was compared with the measured rate of Ca2+ uptake in the basal state, and with the measured lanthanide-insensitive component of divalent cation uptake stimulated by 2,5-di-tert-butylhydroquinone (DBHQ), an inhibitor of the smooth endoplasmic reticulum (Ca2+ + Mg2+)ATP-ase. Fluid uptake by pinocytosis was measured using [14C]sucrose. In hepatocytes incubated at 20°C, DBHQ increased the initial rate of sucrose uptake by about 35%. The data for sucrose uptake were used to calculate the volume of extracellular fluid taken up by pinocytosis which, in turn, was used to predict the amount of extracellular Ca 2+ taken up through pinocytosis in the basal and DBHQ-stimulated states. Rates of divalent cation inflow in the basal state were determined at 20°C by measuring the uptake of 45Ca2+. The degree of stimulation of Ca2+ inflow by DBHQ and the lanthanide-insensitive component of DBHQ-stimulated divalent cation inflow were determined by measuring the rate of Mn2+-induced quenching of intracellular quin-2 in the absence of an agonist, and in the presence of DBHQ or DBHQ plus Gd3+. It was calculated that the process of pinocytosis accounts for at least 15% of Ca2+ uptake in the basal (no agonist) state, and for about 10% of DBHQ-stimulated lanthanide-insensitive Ca2+ uptake. It is concluded that in isolated hepatocytes (i) the release of Ca2+ from intracellular stores stimulates pinocytosis and (ii) the process of pinocytosis can account for a substantial proportion of basal Ca2+ inflow and a small proportion of DBHQ-stimulated lanthanide-insensitive Ca2+ inflow. Kluwer Academic Publishers, 1996 pinocytosis nationallicence [14C]sucrose uptake nationallicence 2,5-di-tert-butylhydroquinone nationallicence 45Ca2+ uptake nationallicence Mn2+ uptake nationallicence rat hepatocytes nationallicence RACC : receptor-activated Ca2+ channel nationallicence DBHQ : 2,5-di-tert-butylhydroquinone nationallicence [Ca2+] : intracellular free Ca2+ concentration nationallicence Fernando Kekulu Department of Medical Biochemistry, School of Medicine, Flinders University, G.P.O. Box 2100, 5001, Adelaide, South Australia, Australia aut Barritt Greg Department of Medical Biochemistry, School of Medicine, Flinders University, G.P.O. Box 2100, 5001, Adelaide, South Australia, Australia aut Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www/wkap.nl 162/1(1996-03-01), 23-29 0300-8177 162:1<23 1996 162 11010 https://doi.org/10.1007/BF00250992 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00250992 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Fernando Kekulu Department of Medical Biochemistry, School of Medicine, Flinders University, G.P.O. Box 2100, 5001, Adelaide, South Australia, Australia aut NATIONALLICENCE 700 1- Barritt Greg Department of Medical Biochemistry, School of Medicine, Flinders University, G.P.O. Box 2100, 5001, Adelaide, South Australia, Australia aut NATIONALLICENCE 773 0- Molecular and Cellular Biochemistry Kluwer Academic Publishers; http://www/wkap.nl 162/1(1996-03-01), 23-29 0300-8177 162:1<23 1996 162 11010 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer