| Popis: |
As in all other cells of the mammalian body, [Ca2+] within renal epithelial cells is maintained at a level far below that in extracellular fluid. Whereas extracellular fluid [Ca2+] is less than 1 mM, [Ca2+] in intracellular fluid is approximately four orders of magnitude lower. Measurements of cytosolic Ca ion concentration have been obtained in vivo with ion-selective microelectrodes (Lee et al., 1980, Lorenzen et al., 1984, Yang et al., 1988) in proximal tubules of Necturus, and with a variety of Ca sensitive indicators in mammalian renal epithelia in culture or in tubule suspensions or isolated nephron segments (Bonventre et al., 1986, Borle and Snowdowne 1982, Bourdeau and Lau 1989, Burnatowska-Hledin and Spielman 1987, Chase and Wong 1988, Dolson et al., 1985, Dominguez et at, 1989, Hruska et al., 1987, Mandel and Murphy 1984, Murphy et al., 1986, Murphy and Mandel 1982, Sakhraui et al., 1985, Shayman et al., 1986, Tang and Weinberg 1986, Taniguchi et al., 1989a and 1989b, Teitelbaum and Berl 1986). Values obtained, range between 70 and 450 nM, with the majority of studies reporting average concentrations of 100 to 200 nM. |
