Intracellular pH regulation of newborn rat skin basal cells

The regulation of intracellular pH (pHi) was examined in newborn rat skin basal cells. When basal cells were acid-loaded by externally applied weak acid or by pretreatment with NH4+, the pHi recovered toward its resting value. This recovery was accompanied by Na+ influx and H+ efflux. The recovery of pHi and concomitant Na+/H+ fluxes were reversibly inhibited by amiloride. Other ionic flux inhibitors 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and furosemide slightly inhibited the pHi recovery from an acid load. The recovery rate from an acid load depended on the concentration of the external Na+.Li+ could substitute for Na+ in the pHi recovery, but K+ had no effect on the recovery. The keratin synthesis of basal cells was decreased by amiloride, and this decrement was deduced to be due to the acidification of the intracellular space. Although ascorbic acid had no effect on the pHi recovery of basal cells, it enhanced the keratin synthesis of the cells. Moreover, an inhibitor of the collagen synthesis, cis-hydroxyproline, suppressed the keratin synthesis but had no effect on the pHi recovery. We therefore believe that the keratin synthesis of the cells was also regulated by the environment, which was formed by the synthesized collagen. Thus, the pHi in the skin basal cells was regulated by the amiloride-sensitive exchange system, and this system seems to be involved in the keratin synthesis.