ISSN:
1432-1351
Keywords:
Ca2+
;
Calcium binding
;
Ciliary activation
;
Hyperpolarization
;
Voltage clamp
;
Ciliate
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Motor responses of cirri (= organelles consisting of bundles of cilia) in the protozoan Stylonychia are elicited by positive or negative shifts of the membrane voltage from its resting state. The same responses are evoked at voltages near the Ca2+ equilibrium potential (ECa) applying extremely positive steps under voltage clamp. Motor responses recorded at large positive voltages approaching ECa from the negative side corresponded to cirral activation following physiological depolarization from the resting potential (DCA). The hyperpolarization-induced activation of the cirri (HCA) was documented during step potentials positive to ECa, suggesting that the observed HCA of the cirri resulted from an efflux of Ca2+ from the ciliary space as compared with DCA, which is related to Ca2+ influx. The ciliary responses were graded functions of the rising outward or inward driving force for Ca2+. Slopes of reciprocal plots of response latencies near ECa as a function of membrane potential indicate a removal of Ca2+ during HCA which exceeds the free intraciliary Ca2+ content at rest. It is suggested that this excess Ca2+ is released from axonemal binding sites.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00224358
