Characterization of Intracellular Ca2+ Increase in Response to Progesterone and Cyclic Nucleotides in Mouse Spermatozoa1

Abstract

Rises in intracellular Ca(2+) concentration ([Ca(2+)](i)) caused by progesterone, an inducer of the acrosome reaction, or by cyclic nucleotides, possible second messengers, were investigated by Ca(2+) imaging of the head of individual mouse sperm. Progesterone induced a [Ca(2+)](i) rise in a dose-dependent manner (4-40 microM), primarily in the postacrosomal region. For 20-microM progesterone, Ca(2+) responses occurred in 42% of sperm, separated into two types: transient type (60% of responding cells; duration, 1-1.5 min; mean amplitude, 335 nM) and prolonged type (40%; >3 min; 730 nM). Prolonged responses required higher doses of progesterone, and their occurrence was enhanced significantly by preincubation for 2-4 h as compared with transient responses. 8-Bromo-cGMP (0.3-3 mM) induced a [Ca(2+)](i) rise more effectively than did 8-bromo-cAMP. For 1-mM 8-bromo-cGMP, 90% of cells exhibited transient Ca(2+) responses (approximately 1 min; 220 nM), independently of the preincubation time. In Ca(2+)-free medium, most sperm showed no Ca(2+) response to progesterone and 8-bromo-cGMP. Pimozide, a Ca(2+) channel blocker, completely blocked prolonged responses and partially inhibited transient responses. These results suggest that progesterone activates at least two distinct Ca(2+) influx pathways, with fast or slow inactivation kinetics, and some sperm show both types of response. A cyclic nucleotide-mediated process could participate in the progesterone-induced [Ca(2+)](i) rise.

Particulate Adenylate Cyclase Plays a Key Role in Human Sperm Olfactory Receptor-mediated Chemotaxis

“…The average bourgeonal signal was 26% (50 M) or 54% (500 M) of the Ca 2ϩ response caused by progesterone (30 M; Fig. 4a), an important component of human follicular fluid that is known to induce sperm acrosome reaction via indirect opening of different membrane Ca 2ϩ channels (31). This progesterone-induced control signal was unaffected by 90-s preincubation with 3 mM SQ22536 (n ϭ 10; Fig.…”

Calcium Channels in the Development, Maturation, and Function of Spermatozoa

“…The A3 and B1 subunits were localized within the flagellum of mature mouse spermatozoa (285). Addition of permeable cGMP to mouse spermatozoa provoked [Ca 2ϩ ] i increases dependent on [Ca 2ϩ ] e , while cAMP was less effective (295,558). Curiously, spermatozoa from CatSper null mice do not present this response (432), and the A3 null mice are fertile (285).…”

Mobilisation of stored calcium in the neck region of human sperm a mechanism for regulation of flagellar activity

“…However, studies of Ca 2+ -regulation in sperm suggest that the 'standard' components and Ca 2+ -signaling capabilities are retained, though possibly in modified form (Wennemuth et al, 2003;Publicover et al, 2007). Immunohistochemistry and Western blotting experiments show that several types of VOCCs are present (Felix, 2005;Jagannathan et al, 2006) and there is also good evidence for expression of ligand-activated channels (Meizel, 2004) and cyclic nucleotide-regulated channels (Weyand et al, 1994;Gauss et al, 1998;Galindo et al, 2000;Kobori et al, 2000) in mammalian and invertebrate sperm, In addition, a number of studies have shown that capacitative Ca 2+ influx occurs in sperm (Blackmore, 1993;1999;Dragileva et al, 1999;O'Toole et al, 2000;Rossato et al, 2001), indicating that store-operated channels are also present. Ca 2+ -ATPase extrusion pumps in the plasma membrane are probably the greatest contributors to Ca 2+ buffering in mammalian sperm (Wennemuth et al, 2003) and are potentially involved in regulating [Ca 2+ ] changes during capacitation (Fraser and McDermott, 1992;DasGupta et al, 1994).…”