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#sperm capacitation

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Fertilization in mammals-l

Ions primarily increasing during capacitation:

Biochemical hallmarks of capacitation include elevated intracellular bicarbonate and calcium concentrations. Bicarbonate enters via Na/HCO3 cotransporters activating soluble adenylyl cyclase producing cAMP which stimulates PKA tyrosine phosphorylation cascade promoting membrane fluidity and CatSper priming. Concurrent increase in intracellular pH and calcium influx prepares sperm for hyperactivation and acrosome exocytosis. Removal of cholesterol by albumin accelerates ion permeability. These ionic shifts are measurable in vitro and are required for fertilizing ability, distinguishing capacitated from non-capacitated populations experimentally for assisted reproduction technologies, diagnostics, semen analysis in clinical laboratories and fertility assessment protocols.

Ref: Austin & Bavister, Exp Cell Res: Bicarbonate, calcium rise and tyrosine phosphorylation during sperm capacitation events.

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Fertilization in mammals-l

Capacitation of sperm in mammals occurs in:

Capacitation is obligatory final maturation sperms must undergo within female tract before fertilization capability. After ejaculation sperm reside in uterus and oviduct where albumin extracts membrane cholesterol, bicarbonate activates soluble adenylyl cyclase increasing cAMP, protein kinase A phosphorylates tyrosine residues. Ion permeability increases, intracellular pH rises, CatSper channels primed for hyperactivation. Removal of decapacitation factors from epididymal fluid exposes receptors for zona. Only capacitated sperm can undergo acrosome reaction upon encountering ZP. Thus tract provides conditions conferring fertile competence, membrane destabilization, signaling activation essential for conception and gamete fusion success.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Capacitation in female tract and cholesterol efflux mechanisms.

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Fertilization in mammals-ll

Mammalian sperm capacitation occurs primarily in:

Capacitation is a final functional maturation occurring only within female reproductive tract fluids of uterus and oviduct after epididymal transit. Albumin acts as cholesterol acceptor, extracting cholesterol from sperm plasma membrane, increasing fluidity and permeability. Bicarbonate influx activates soluble adenylyl cyclase, elevating cAMP, stimulating PKA-dependent tyrosine phosphorylation cascades. Membrane remodeling opens CatSper calcium channels, promotes hyperactivated motility and primes acrosomal responsiveness, conferring true fertilizing ability solely after exposure to female environment essential for successful conception, implantation competence and embryonic development initiation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Fertilization – capacitation and sperm activation in female tract.

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