| 1. |
- Kass, G E, et al.
(författare)
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Receptor-mediated Mn2+ influx in rat hepatocytes : comparison of cells loaded with Fura-2 ester and cells microinjected with Fura-2 salt
- 1994
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 302, s. 5-9
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Tidskriftsartikel (refereegranskat)abstract
- In single Fura-2 ester-loaded hepatocytes, stimulation by vasopressin, but not emptying of the agonist-sensitive Ca2+ store by 2,5-di-(t-butyl)hydroquinone, resulted in an increase in the rate of Fura-2 fluorescence-quenching by Mn2+. Similarly, in cells microinjected with Fura-2 salt, vasopressin stimulated Mn2+ entry while 2,5-di-(t-butyl)hydroquinone or thapsigargin did not. The pattern of Fura-2 quenching by Mn2+ only correlated with the movement of Mn2+ across the plasma membrane.
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| 2. |
- Kass, G E, et al.
(författare)
-
Two separate plasma membrane Ca2+ carriers participate in receptor-mediated Ca2+ influx in rat hepatocytes.
- 1994
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Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 1878-2434. ; 1223:2, s. 226-33
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Tidskriftsartikel (refereegranskat)abstract
- The plasma membrane Ca2+ carrier system involved in receptor-mediated Ca2+ entry was studied. Using the Ca2+ readdition protocol, the rate of cytosolic free Ca2+ concentration ([Ca2+]i) increase in vasopressin-pretreated hepatocytes was significantly higher than in thapsigargin- or 2,5-di(tert-butyl)hydroquinone-pretreated cells. The addition of Mn2+ to unstimulated hepatocytes resulted in a biphasic quench of fura-2 fluorescence. After an initial phase that was fast in rate but of short duration, the rate of fura-2 quench by Mn2+ became much slower and lasted until all the cellular fura-2 was quenched. Pretreatment of the cells with vasopressin only accelerated the rate of the latter phase but not of the initial one. In agonist-stimulated cells, acidification of the extracellular medium or the presence of ruthenium red, econazole or SK&F 96365 decreased the rates of both [Ca2+]i increase and Mn2+ entry upon addition of the respective cation. By contrast, neomycin and N-tosyl-L-phenylalanine chloromethyl ketone markedly decreased the rate of [Ca2+]i increase upon Ca2+ readdition but had no effect on vasopressin-stimulated Mn2+ entry. None of the treatments affected the ability of vasopressin and thapsigargin to mobilize the internal Ca2+ store. It is concluded that in hepatocytes the two pathways of receptor-mediated Ca2+ entry control two distinct yet pharmacologically related cation carriers.
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