. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BIVALVE MYOCYTE INTRACELLULAR pH REGULATION 213 rapid as the peak acidosis occurred within 3 min (Fig. 4). Thus, it is likely that pH, recovery processes would po- tentially produce only minor errors in /}NB determination in this system. Recovery from acid loading Isolated myocytes regulate pH, after acid-loading as ev- idenced by the slow alkalinization following NH4C1 wash- out using normal MASW ([HCO, ] approximately mM) (Fig. 5A; Table 1). However, the rate of alkaliniza- tion was greatly accelerated during wash-out
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BIVALVE MYOCYTE INTRACELLULAR pH REGULATION 213 rapid as the peak acidosis occurred within 3 min (Fig. 4). Thus, it is likely that pH, recovery processes would po- tentially produce only minor errors in /}NB determination in this system. Recovery from acid loading Isolated myocytes regulate pH, after acid-loading as ev- idenced by the slow alkalinization following NH4C1 wash- out using normal MASW ([HCO, ] approximately mM) (Fig. 5A; Table 1). However, the rate of alkaliniza- tion was greatly accelerated during wash-out using CO:/4 mA/ HCO3 MASW (Fig. 5B; Table I). Recovery from acid loading did not appear to be dependent on ex- ternal Na+, as the recovery rate was essentially the same for MASW and Na+-free MASW (Table I). SITS com- pletely blocked recovery. In fact, there was a gradual re- duction in pH, once the plateau acidification after wash- out had been attained (Table I). Collectively, these results show that it is likely that a SITS-sensitive HCO3":CI~ ex- changer plays a major role in recovery from acid loading in M. campechiensis myocytes. Discussion Molluscan myocytes have been used on a number of occasions as experimental systems for investigating phys- iological phenomena ranging from ion channels (Brezden eta/., 1986) to changes in intracellularCa:+ concentrations during contraction (Ishii el a/.. 1989). In this regard, car- diac myocytes from M. campechiensis appear to be an ideal model system for studies of regulation of pH, in that these cells are easily isolated, retain viability for extended time periods and, of course, can maintain acid-base bal- ance in spite of extracellular and intracellular pH distur- bances. The average pH, of in these cells as deter- mined by BCECF-imaging is comparable to values ob- served in various marine gastropod muscles (Ellington, 1983b; Graham and Ellington, 1985; Wiseman and El- pHi 20 30 time (mm) 10 20 time (mm)
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
