Taurine release associated to volume regulation in rabbit lymphocytes

Abstract

Rabbit lymphocytes exposed to hyposmotic media first swell and then recover their initial volume within 6 min. During volume recovery, free amino acids (FAA) decrease from 451.1 to 208 nmoles/mg protein. Taurine was the dominating FAA, accounting for 70% of the FAA pool. The time course of 3H-taurine release induced by hyposmolarity followed that of volume recovery. Efflux of 3H-taurine in an 8 min period was 17.8% (of total labeled taurine accumulated during loading) in an isosmotic medium. Reducing osmolarity to 0.87, 0.75, 0.62, and 0.5 increased this release to 24.8%, 38.1%, 56.4% and 70.9%, respectively. The volume-sensitive release of 3H-taurine was unaffected by omission of external Na+ or Ca++ and was reduced by 23% in the absence of Cl-. It was unaffected by agents disrupting the cytoskeleton or by tetraethylammonium, barium, quinidine, and gadolinium, but was 26% reduced by DIDS. Taurine release was inhibited at 4 degrees C, but was unchanged at 15 degrees C or 25 degrees C. An involvement of FAA, particularly taurine, in lymphocyte volume regulation is suggested.

External Cl^--Dependent Formation of Watery Vacuoles by Long-Term Hypotonic Shock in 3T3-L1 Cells

“…Exclusion of Cl -contributes to RVD responses. Regulatory volume increase (RVI) is mediated by transport of Na + and Cl -through cotransporter and exchanger [10][11][12]. Results obtained in this study indicate that DPC-sensitive transport of Cl -, but not Na + , is related to the vacuole formation in the cells with the hypotonic stress.…”

“…RVD is mediated by the rapid extrusion of osmolytes such as K + , Cl -and amino acid through ion channels, exchangers and cotransporters [6,[10][11][12]32]. Blockers for Cl -channels inhibit the chloride efflux, taurine efflux and RVD response [33].…”

“…Osmolytes such as taurine are excreted for the recovery from cell swelling, termed the long-term RVD [10][11][12][13]. Initial RVD and long-term RVD result from the activation of transporters and channels for ions and osmolytes, but other mechanisms in addition to the activation of transporters and channels might contribute to the regulation of water content in the cytoplasm for a long period of hypotonic shock.…”

Volume‐regulatory taurine release from a human lung cancer cell line

“…Osmotic swelling of human lung epithelial cancer (Sl) cells was shown here to result in the activation of a pathway which mediated the ehlux of the non-essential sulfonic amino acid, taurine. In this respect Sl cells resemble a wide variety of other mammalian cell-types including epithelial [ 17,181, brain [20,22,24] and blood [19] cells, as well as numerous lower vertebrate and marine invertebrate cells (reviewed by Chamberlin and Strange [42]). In Sl cells swollen in a low K' saline the volume-activated efflux component declined steadily with time so that within 40-80 min the flux in the hypo-osmotic solution had reverted to the basal level measured under iso-osmotic conditions (Fig.…”

“…In vertebrate cells the primary organic 'osmolyte' is usually tam-me, a sulfonic amino acid which may be present in the cytoplasm at concentrations of up to 40 mM [3]. Volume-activated taurine release has been demonstrated from many vertebrate cells and tissues including fish erythrocytes, heart, brain and hepatocytes [4-121, bird erythrocytes [13], Ehrlich ascites tumour cells MDCK cells [17,18], rabbit lymphocytes [19], and a variety of mammalian brain cell-types . These studies have revealed a number of common characteristics for the transport mechanisms which mediate volume-activated taurine release from different cells: they are, in general, Na'-independent, non-saturable and not prone to 'trans-stimulation' [6,1.5,18,22,25].…”