Hyperpolarization/depolarization on human spermatozoa.
The accumulation of the lipophilic cation radiolabeled triphenylmethylphosphonium (TPMP+) was utilized to determine the resting membrane potential across the plasma membrane (psi) of human sperm. Washed sperm were suspended and incubated in low-K+ and high-K+ medium and allowed to take up the cation to a steady state (20 min at 37 degrees C). By using this differential, the value obtained was inserted in the Nernst equation and the value yielded a psi of -69 +/- 2 mV. When the Na+ or K+ concentration is high in the medium, the accumulation of TPMP+ in the membrane sperm cells was increased or decreased, respectively, inducing hyperpolarization and depolarization of the membrane 20% and 85%, respectively. The presence of divalent cations Zn++ and Mg++ in the incubation medium both induced a hyperpolarization of 10% and 8.6%, respectively. The addition of specific reagents such as p-chloromercuribenzenosulfonate and ethylenediaminetetraacetic acid sodium salt both decreased the psi 35% and 58%, respectively. The agents acting on the sperm cell membrane, such as dithiothreitol and progesterone, both induced hyperpolarization and depolarization of the membrane 16% and 40%, respectively. The presence of propranolol and L-alpha-lysophosphatidylcholine, which affect the ionic gradients present across the plasma membrane, both induced a depolarization from 43% and 92%, respectively. Finally the psi was glucose-dependent. The result of these studies was that, by the use of agents causing hyperpolarization or depolarization, we obtained changes in the psi of -83.4 +/- 2.2 mV, until -6 +/- 0.6 mV changes of -76.8 +/- 2 mV translated across the sperm cell membrane.
Calzada
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Unidad de Investigación Clínca en Enfermedades Endocrinas, Hospital de Gineco-Obstetricia No. 4, Tizapán, Mexico, D.F.
Salazar
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Macias
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D002412:Cations; D002462:Cell Membrane / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009861:Onium Compounds / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013094:Spermatozoa / Q000502:physiology*; D014320:Triphenylmethyl Compounds / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology
D002412:Cations; D008244:Lysophosphatidylcholines; D009861:Onium Compounds; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D011374:Progesterone; D012964:Sodium; D011433:Propranolol; D008274:Magnesium; D005947:Glucose; D015032:Zinc; D011188:Potassium