Regulatory volume increase in rat lacrimal gland acinar cells.

Abstract

The volume of acinar cells isolated from rat lacrimal glands was measured during hypertonic shock. Cells shrank in hypertonic solutions, but a regulatory volume increase (RVI) was only observed under certain conditions. In HEPES-buffered solutions at 37 degrees C, an RVI was observed. This was inhibited by 20 microM bumetanide, an inhibitor of Na(+)-K(+)-2Cl- cotransport. RVI did not occur in HEPES-buffered solutions at 20 degrees C suggesting that Na(+)-K(+)-2Cl- cotransport is inactive at this temperature. In HCO3- buffered solutions however, an RVI was observed at 20 degrees C. In these conditions, the RVI was inhibited by 500 microM 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid (H2-DIDS) and 10 microM 5-(N-methyl-N-isobutyl)-amiloride (MIBA) indicating the involvement of Cl(-)-HCO3- exchange and Na(+) -H+ exchange respectively. RVI was also supported by a mixture of neutral amino acids, and by the nonmetabolizable amino acids 5 mM alpha-(methylamino)isobutyric acid (MeAIB) and 5 mM alpha-aminoisobutyric acid (AIB). These data suggest that the accumulation of amino acids, possibly by the system A Na(+)-coupled amino acid cotransporter, contributes to RVI in these cells. In conclusion, rat lacrimal gland acinar cells are capable of undergoing RVI following shrinkage by hypertonic shock.