title: Effects of arachnotoxin on intracellular pH and calcium in human spermatozoa.
abstract: OBJECTIVE
  To determine the effect of arachnotoxin (ATx), a venom extracted from the Chilean spider Latrodectus mactans, on intracellular calcium ([Ca(2+)](i)) and pH (pH(i)) in capacitated human spermatozoa.
  
  
  METHODS
  Spermatozoa were collected from fertile adult men (n = 8). Mobile spermatozoa were collected by the "swim up" technique and stimulated with the crude extract of ATx and with progesterone (P).
  
  
  METHODS
  Hospital of the Federal University of São Paulo, São Paulo, Brazil.
  
  
  METHODS
  [Ca(2+)](i) was measured in fura2-AM-loaded spermatozoa, and pH(i) was measured in spermatozoa loaded with the pH-sensitive dye [(2',7')-bis (carboxymethyl)-(5,6)-carboxyfluorescein]-AM (BCECF).
  
  
  RESULTS
  The ATx and P induced a biphasic change in [Ca(2+)](i) consisting of a peak followed by a small but sustained elevation. The response to ATx was greatly reduced by pretreatment with P. The ATx caused intracellular acidification, whereas P induced alkalinization. Blockade of the NA(+)/H(+) exchanger with ethylisopropylamiloride (EIPA) sharply increased ATx-induced acidification.
  
  
  CONCLUSIONS
  Arachnotoxin increased [Ca(2+)](i) through the opening of calcium channels and release of calcium from intracellular stores. The ATx reduced pH(i) in human sperm, possibly by inhibiting the Na(+)/H(+) exchanger.
authors.affiliation: Center of Reproductive Biotechnology, Department of Preclinical Sciences, Faculty of Medicine, Universidad de La Frontera, Temuco, Chile.
authors.forename: Fernando
authors.initials: F
authors.lastname: Romero
authors.forename: Maria Adelaide
authors.initials: MA
authors.lastname: Cunha
authors.forename: Raul
authors.initials: R
authors.lastname: Sanchez
authors.forename: Alice Teixeira
authors.initials: AT
authors.lastname: Ferreira
authors.forename: Nestor
authors.initials: N
authors.lastname: Schor
authors.forename: Maria Etsuko Miyamoto
authors.initials: ME
authors.lastname: Oshiro
mesh_terms: D020101:Acrosome Reaction / Q000187:drug effects*; D000328:Adult; D002118:Calcium / Q000378:metabolism*; D005452:Fluoresceins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D013075:Sperm Capacitation / Q000187:drug effects*; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D013111:Spider Venoms / Q000633:toxicity*
chemical_list: D005452:Fluoresceins; D013111:Spider Venoms; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D002118:Calcium