Influence of pentachlorophenol on light emission from single barnacle muscle fibers preloaded with aequorin.
Experiments show that the resting ouabain-insensitive sodium efflux in giant fibers from the barnacle Balanus nubilus is stimulated by external application of pentachlorophenol (PCP). This work has now been extended to include a study of muscle fibers preloaded with the Ca2+ indicator aequorin to determine whether PCP is able to increase light emission; and whether its potency depends on the number of chlorine atoms and external pH. The results obtained are as follows: 1) PCP causes a dose-dependent, multiphasic rise in light emission; the threshold concentration in fibers not poisoned with ouabain was in the low micromolar range. 2) The efficacy of PCP is considerably greater than that of less-chlorinated phenols and phenol. 3) The response to PCP is a sigmoidal function of external pH both in unpoisoned and ouabain-poisoned fibers. Reducing external pH potentiates its efficacy. 4) The response to PCP depends on the external Ca2+ concentration, and the requirement for Ca2+ is usually absolute.
Bittar
E E
EE
Department of Physiology, University of Wisconsin, Madison 53706.
Wu
J R
JR
D000331:Aequorin; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008163:Luminescent Measurements; D009132:Muscles / Q000187:drug effects*; D009994:Osmolar Concentration; D010416:Pentachlorophenol / Q000494:pharmacology*; D001468:Thoracica
D000331:Aequorin; D010416:Pentachlorophenol; D002118:Calcium