Streptomycin and its analogues are potent inhibitors of the hypotonicity-induced Ca2+ entry and Cl- channel activity.
Streptomycin is a common antibiotic used in culture media. It is also a known blocker of stretch-activated and mechanosensitive ion channels in neurons and cardiac myocytes. But very little information is available on its effect in the regulation of epithelial ion channels. Osmotic swelling is a kind of mechanical stretch. The opening of stretch-activated Ca(2+) channels contributes to hypotonicity-induced Ca(2+) influx which is necessary for the activation of volume-regulated Cl(-) channels in human cervical cancer cells. This study aimed to investigate the role of streptomycin in cell volume regulation. Treatment of cervical cancer SiHa cells with streptomycin and its analogues (gentamicin and netilmicin) did not affect the basal cytosolic Ca(2+) ([Ca(2+)](i)) level. But it attenuated the hypotonicity-stimulated increase of [Ca(2+)](i) in a dose-dependent manner with half-maximal inhibitory concentrations (IC(50)) of 25, 90 and 200 microM for streptomycin, gentamicin and netilmicin, respectively, when measured at room temperature. In contrast, under free extracellular Ca(2+) condition, hypotonic stress only induced a small, progressive increase of [Ca(2+)](i), while 500 microM streptomycin did not affect this Ca(2+) signaling. Streptomycin and its analogues (gentamicin and netilmicin) also inhibited the activation of volume-regulated Cl(-) channels in a dose-dependent manner with IC(50) of 30, 95 and 250 microM at room temperature, respectively. Chronic culture with 50 microM streptomycin downregulates the activity of volume-regulated Cl(-) channels and retards the process of regulatory volume decrease in SiHa cells and MDCK cells. We suggest that using cells chronically cultured with streptomycin to study epithelial ion channels risks studying cellular and molecular pathology rather than physiology.
Shen
Meng-Ru
MR
Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan. mrshen@mail.ncku.edu.tw
Chou
Cheng-Yang
CY
Chiu
Wen-Tai
WT
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D045744:Cell Line, Tumor; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002712:Chlorides / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology / Q000379:methods; D005260:Female; D016257:Fura-2 / Q000737:chemistry; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D013307:Streptomycin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013997:Time Factors; D002583:Uterine Cervical Neoplasms / Q000378:metabolism
D018118:Chloride Channels; D002712:Chlorides; D007038:Hypotonic Solutions; D002118:Calcium; D016257:Fura-2; D013307:Streptomycin