Phosphatidylinositol 4,5-bisphosphate hydrolysis in human sperm stimulated with follicular fluid or progesterone is dependent upon Ca2+ influx

Abstract

Hydrolysis of the phospholipid phosphatidylinositol 4,5-bisphosphate is thought to be intimately involved in agonist-induced changes in intracellular Ca2+ levels. Recently we have shown that human preovulatory follicular fluid, which induces exocytosis in human sperm, can stimulate a rapid, transient increase in sperm cytosolic [Ca2+] [Thomas & Meizel (1988) Gamete Res. 20, 397-411]. We report here that both a Sephadex G-75 column fraction, derived from follicular fluid, and progesterone (a component of both the G-75 fraction and whole follicular fluid) stimulate rapid hydrolysis of PtdIns(4,5)P2 and PtdIns4P in human sperm. We also report that progesterone stimulates a rapid influx of Ca2+ in human sperm. Human spermatozoa were labelled for 24 h with myo-[3H]inositol and then treated with either the G-75 fraction or progesterone. A 30-65% loss of label was detected in PtdIns(4,5)P2 and PtdIns4P within 15 s of stimulus addition; no changes were observed in PtdIns during 2 min of treatment. The loss of label from both lipids was accompanied by an increase in water-soluble inositol phosphates. Production of both InsP3 and InsP2 was seen within 10 s; however, InsP3 was rapidly removed and had reached control levels by 1 min. Similarly, formation of InsP2 reached a peak by 30 s and then began a decline accompanied by a corresponding increase in InsP. No increases in InsP4 were seen in sperm treated in this fashion. Stimulated hydrolysis of the phosphoinositides and release of inositol phosphates were both blocked by the Ca2+ antagonist La3+. Likewise, the progesterone-induced increase in intracellular Ca2+ was inhibited by La3+, and phosphoinositide hydrolysis stimulated by this hormone was dependent upon the presence of extracellular Ca2+.

Ultrastructural localization of protein kinase C in human sperm.

“…Signal transduction components have been described in mammalian sperm (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Recently, we have found PKC and some of its subspecies in human sperm.…”

Mouse sperm membrane potential: changes induced by Ca2+

“…Changes in intracellular Ca 2÷ ([Ca2+]i) and intracellular pH (pHi) are fundamental for mammalian sperm motility [1,2], and for the AR induced with the zona pellucida glycoproteins [3] or with progesterone [4,5]. Some of the possible protagonists responsible for these ionic permeability changes are: ion channels for Ca 2÷ [6][7][8]; K + [1,9], CI- [10] and one for cations gated by cyclic nucleotides [11].…”

rab3‐Peptide stimulates exocytosis of the ram sperm acrosome via interaction with cyclic AMP and phospholipase A2 metabolites

“…Treatment with these agonists, including A23187/Ca 2+, results in a rapid generation of diacylglycerol (DAG) due to the hydrolysis of polyphosphoinositides by phosphoinositidase C [3,[6][7][8] and hydrolysis of phosphatidylcholine by a specific phospholipase C [3,8,9]. No evidence for the participation of the phospholipase D/phosphatidic acid phosphohydrolase pathway in the generation of DAG has been found [3].…”