Two separate plasma membrane Ca2+ carriers participate in receptor-mediated Ca2+ influx in rat hepatocytes.

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.

Chow, S C (author)
Gahm, A (author)
Webb, Dominic-LucRolf Luft Center for Diabetes Research, Department of Endocrinology, Karolinska Institutet, Stockholm, Sweden(Swepub:uu)domwe127 (author)
Berggren, P O (author)
Llopis, J (author)
Orrenius, S (author)
Rolf Luft Center for Diabetes Research, Department of Endocrinology, Karolinska Institutet, Stockholm, Sweden (creator_code:org_t)

In:Biochimica et Biophysica Acta: Elsevier BV1223:2, s. 226-330006-30021878-2434
In:Biochimica et Biophysica Acta (BBA) - Molecular Cell Research: Elsevier BV1223:2, s. 226-330167-4889

By the author/editor: Kass, G E; Chow, S C; Gahm, A; Webb, Dominic-Lu ...; Berggren, P O; Llopis, J; show more...; Orrenius, S; show less...

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