Gadolinium, a mechano-sensitive channel blocker, inhibits osmosis-initiated motility of sea- and freshwater fish sperm, but does not affect human or ascidian sperm motility.
Exposure to hypo-osmotic or hyperosmotic environment triggers the initiation of fish sperm motility. In this article, we report that calcium and potassium channel blockers do not influence motility of puffer fish sperm but calmodulin antagonists reversibly decrease it, suggesting that calmodulin-Ca(2+) interactions are prerequisite for the initiation of sperm motility in this species. Gadolinium (a stretch activated ion channel blocker) decreased the motility of puffer fish sperm from 92 +/- 3% to 6 +/- 3% and that of carp sperm from 91 +/- 7% to 3.5 +/- 4.3% in a dose-dependent manner (10-40 micro M). The effect of gadolinium was reversible, suggesting that stretch activated ion channels participate in the initiation of sperm motility of the two species. Gadolinium inhibits changes in the isoelectric point of certain proteins of puffer fish sperm, which occur when sperm motility is initiated in a hypertonic solution. Anisotropy measurements showed that hypo-osmotic treatment, which initiates carp sperm motility, increased membrane fluidity. When hypo-osmotic treatment was given in the presence of gadolinium, the sperm membrane remained as rigid as in quiescent cells, while motility was blocked. By contrast, gadolinium did not influence the motility parameters of Ciona or human sperm. Based on these lines of evidence, we suggest that conformational changes of mechanosensitive membrane proteins are involved in osmolality-dependent but not osmolality-independent sperm.
Krasznai
Zoltán
Z
Department of Biophysics and Cell Biology, Medical and Health Science Centre, University of Debrecen, Debrecen, Hungary. krasznai@jaguar.dote.hu
Morisawa
Masaaki
M
Krasznai
Zoárd Tibor
ZT
Morisawa
Sachiko
S
Inaba
Kazuo
K
Bazsáné
Zsuzsa Kassai
ZK
Rubovszky
Bálint
B
Bodnár
Béla
B
Borsos
Antal
A
Márián
Teréz
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002347:Carps / Q000502:physiology; D002938:Ciona intestinalis / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005682:Gadolinium / Q000494:pharmacology*; D006801:Humans; D015640:Ion Channel Gating; D008297:Male; D008560:Membrane Fluidity; D009997:Osmotic Pressure; D013081:Sperm Motility / Q000187:drug effects*; D023741:Takifugu / Q000502:physiology
D005682:Gadolinium; D002118:Calcium