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A Role of Plasminogen Activators in Animal Reproductive Cells and Organs

  • HwangBo, Yong (College of Animal Life Sciences, Kangwon National University) ;
  • Cheong, Hee-Tae (College of Veterinary Medicine, Kangwon National University) ;
  • Yang, Boo-Keun (College of Animal Life Sciences, Kangwon National University) ;
  • Park, Choon-Keun (College of Animal Life Sciences, Kangwon National University)
  • Received : 2014.06.02
  • Accepted : 2014.06.17
  • Published : 2014.06.30

Abstract

Plasminogen activators (PAs) are serine proteases that convert plasminogen to plasmin. Two type of PAs are urokinase-type PA (uPA) and tissue-type PA (tPA). Plasminogen is present in most extracellular fluids. PAs play in various reproductive processes including implantation, ovulation and fertilization. In the spermatozoa, PAs and PAIs play a role in sperm motility and fertilization. PAs in the sertoli cell are stimulated spermatozoa maturation and sperm activation through the phospholipase A2. The oocyte maturation is the process for fertilization and implantation. PAs in cumulus-oocyte complexes (COCs) are related to oocyte maturation by protein kinase A and C. In the ovulatory process, PAs activity are changed and it are related to reducing the tensile strength of ovarian follicle wall. The uterine environment is important for reproduction and the uterus undergo tissue remodeling. In the uterus and oviduct of mammals, expression and activity of PAs are changed during estrous cycle. Thus, expression and activity of PAs are concerned to many reproductive functions. Therefore, PAs seem to important factor of regulator in reproductive events.

Keywords

References

  1. Aflalo E, Sod-Moriah U, Potashnik G, Har-Vardi (2005): Expression of plasminogen activators in preimplantation rat embryos developed in vivo and in vitro. Reprod Biol Endocrinol 3:7. https://doi.org/10.1186/1477-7827-3-7
  2. Ann JY, Sa SJ, Cao Y, Lee SY, Cheong HT, Yang BK, Park CK (2006): Effects of cumulus cells and follicular fluid on plasminogen activator activity during in vitro maturation of porcine oocytes. Reprod Dev Biol 30:135-141.
  3. Appella E, Robinson E, Ullrich S, Stoppelli M, Corti A, Cassani G, Blasi F (1987): The receptor-binding sequence of urokinase: a biological function for the growth factor module of proteases. J Biol Chem 262:4437-4440.
  4. Bachmann F (1987): Fibrinolysis. In; Thrombosis and Haemostasis. Verstrate M, Vermylen J, Lijnen H, Arnout J (Ed.). Int Soc. On thrombosis and haemostasis and leuven press. Leuven pp.227-265.
  5. Baskar JF, Torchiana DF, Biggers JD, Corey EJ, Andersen NH, Subramanian N (1981): Inhibition of hatching of mouse blastocysts in vitro by various prostaglandin antagonists. J Reprod Fertil 63:59-363.
  6. Beers WH (1975): Follicular plasminogen and plasminogen activator and the effect of plasmin on ovarian follicle wall. Cell 6:379-386. https://doi.org/10.1016/0092-8674(75)90187-7
  7. Bugge TH, Flick MJ, Daugherty CC, Dengen JL (1995): Plasminogen deficiency causes severe thrombosis but is compatible with development and reproduction. Gene Dev 9:794-807. https://doi.org/10.1101/gad.9.7.794
  8. Carmeliet P, Collen D (1996): Gene manipulation and transfer of the plasminogen and coagulation system in mice. Semin Thromb Hemost 22:525-542. https://doi.org/10.1055/s-2007-999055
  9. Carmeliet P, Schoonjans L, Kiechens L, Ream B, Degen J, Bronson R, De VR, Van DOJJ, Collen D, Mulligan RC (1994): Physiological consequences of loss of plasminogen activator gene function in mice. Nature 368:419-424. https://doi.org/10.1038/368419a0
  10. Casslen B, Nordengren J, Gustavsson B, Nilbert M, Lund LR (1995): Progesterone stimulates degradation of urokinase plasminogen activator (u-PA) in endometrial stromal cells by increasing its inhibitor (PAI- 1) and surface expression of the u-PA receptor. J Clin Endocrinol Metab 80:2776-2784.
  11. Collen D (1980): On the regulation and control of fibrinolysis. Thromb Maemostas 43:77-79.
  12. Collen D (1985): Human tissue-type plasminogen activator: from the laboratory to the bedside. Circulation 72:18-20. https://doi.org/10.1161/01.CIR.72.1.18
  13. Collen D, Lijnen H (1986): The fibrinolytic system in man. CRC Crit Rev Oncol Hemat 4:249-301. https://doi.org/10.1016/S1040-8428(86)80014-2
  14. Dano K, Andreasen PA, Grondahl-Hansen J, Kristensen P, Neilson LS, Skriver L (1985): Plasminogen activators, tissue degradation, and caner. Adv Cancer Res 44:139-266. https://doi.org/10.1016/S0065-230X(08)60028-7
  15. Dow MPD, Bakke LJ, Cassar CA, Peters MW, Pursley JR, Smith GW (2002): Gonadotropin surge-induced up-regulation of the plasminogen activators (Tissue plasminogen activator and urokinase plasminogen activator) and the urokinase plasminogen activator receptor within bovine periovulatory follicular and luteal tissue. Biol Reprod 66:1413-1421. https://doi.org/10.1095/biolreprod66.5.1413
  16. Ebisch I, Steegers-Theunissen R, Sweep F, Zielhuis G, Geurts-Moespot A, Thomas C (2007): Possible role of the plasminogen activation system in human subfertility. Fertil Steril 87:619-626. https://doi.org/10.1016/j.fertnstert.2006.07.1510
  17. Fazleabas AT, Geisert RD, Bazer FW (1983): Relationship between release of plasminogen activator and estrogen by blastocysts and secretion of plasmin inhibitor by uterine endometrium in pregnant pig. Bio Reprod 29:222-238.
  18. Feng Q, Liu K, Hu ZY, Zou RJ, Yang SC, Liu YX (1993): Possible involvement of tissue-type plasminogen activator in luteolysis of rhesus monkeys. Hum Reprod 8:1640-1644. https://doi.org/10.1093/oxfordjournals.humrep.a137905
  19. Fibbi G, Dini G, Pasquali F, Pucci M, Del RM (1986): The Mr 17500 region of the A chain of urokinase is required for interaction with a specific receptor on A43 cell. Biochim Biophys Acta 885:301-308. https://doi.org/10.1016/0167-4889(86)90245-4
  20. Finlay TH, Katz J, Kirsch L, Levitz M, Nathoo SA, Seiler S (1983): Estrogen-stimulated uptake of plasminogen by the mouse uterus. Endocrinology 112:856-861. https://doi.org/10.1210/endo-112-3-856
  21. Gabler C, Killian GJ, Einspanier R (2001): Differential expression of extracellular matrix components in the bovine oviduct during the oestrus cycle. Reproduction 122:121-130. https://doi.org/10.1530/rep.0.1220121
  22. Gerard R, Chine K, Meidell R (1986): Molecular biology of tissue plasminogen activator and endogenous inhibitors. Molec Biol Med 3:449-457.
  23. Guerette P, Langlais J, Antaki P, Chapdelaine A, Roberts K (1988): Activation of phospholipase A2 of human spermatozoa by proteases. Gamete Res 19:203-214. https://doi.org/10.1002/mrd.1120190210
  24. Gwatkin RBL, William DT, Hartmann JF, Kniazuk M (1973): The zona reaction of hamster and mouse eggs: production in in vitro by a trypsin-like protease from cortical granules. J Reprod Fertil 32:259-265. https://doi.org/10.1530/jrf.0.0320259
  25. Hart DA, Fulton RJ, Cieplak W (1986a): Species differences in the expression of caseinolytic proteinases and plasminogen activators by bone marrow cells. Comp Biochem Phsiol 84B:15-22.
  26. Hart DA, Rehemtulla A, Babins E (1986b): Species differences in the detection of high molecular weight urinary plasminogen. Comp Biochem Phsiol 84B:287-293.
  27. Hu ZY, Liu YX, Liu K, Byrne S, Ny T, Feng Q, Ockleford CD (1999): Expression of tissue-type and urokinase-type plasminogen activators as well as plasminogen activator inhibitor type-1 and type-2 in human and rhesus monkey placenta. J Anat 194:183-195. https://doi.org/10.1046/j.1469-7580.1999.19420183.x
  28. Huang X, Xia W, Xiong C, Xiao D, Shen J, Zhou J (1997): Studies on the relationship between urokinase plasminogen activator (uPA) and human sperm motility. J Tongji Med Univ 17:213-217. https://doi.org/10.1007/BF02895622
  29. Huarte J, Belin D, Bosco D, Sappino AP, Vassalli JD (1987): Plasminogen activator and mouse spermatozoa: urokinase synthesis in the male genital tract and binding of the enzyme to the sperm cell surface. J Cell Biol 104:1281-1289. https://doi.org/10.1083/jcb.104.5.1281
  30. Huarte J, Belin D, Vassalli JD (1985): Plasminogen activator in mouse and rat oocytes: Induction during meiotic maturation. Cell 43:551-558. https://doi.org/10.1016/0092-8674(85)90184-9
  31. Huarte J, Vassalli JD, Belin D, Sakkas D (1993): Involvement of the plasminogen activator/plasmin proteolytic cascade in fertilization. Dev Biol 157:539-546. https://doi.org/10.1006/dbio.1993.1156
  32. Hurst PR, MacFarlane DW (1981): Further effects of nonsteroidal antiinflammatory compounds on blastocyst hatching in vitro and implantation rates in the mouse. Biol Reprod 25:777-784. https://doi.org/10.1095/biolreprod25.4.777
  33. Jimenez Diaz M, Giunta S, Valz-Gianinet J, Pereyra- Alfonso S, Flores V, Miceli D (2000): Proteases with plasminogen activator activity in hamster oviduct. Mol Reprod Dev 55:47-54. https://doi.org/10.1002/(SICI)1098-2795(200001)55:1<47::AID-MRD7>3.0.CO;2-J
  34. Kagitani H, Tagawa M, Hatanaka K, Ikarai T, Saito A, Bando H, Okada H, Matsuo O (1985): Expression in E. coli of fibrin affinity. FEBS Lett 189:145-149. https://doi.org/10.1016/0014-5793(85)80860-7
  35. Kim NH, Menino AR (1995): Effects of protein kinase A and C and modulators of phosphorylation and plasminogen activator activity in porcine oocyte- cumulus cells complexes during in vitro maturation. Mol Reprod Dev 40:364-370. https://doi.org/10.1002/mrd.1080400313
  36. Kobayashi T, Matsuda Y, Park J, Hara I, Kaneko S, Fujimoto Y, Nozawa S, Akihama S (1992): Trypsinlike arginine amidases including plasminogen and plasmin in human seminal plasma by affinity adsorption and elution. Arch Androl 28:165-170. https://doi.org/10.3109/01485019208987694
  37. Kucherlapati R, Tepper R, Granelli PA, Reich E (1978): Modulation and mapping of a human plasminogen activator by cell fusion. Cell 15:1331-1340. https://doi.org/10.1016/0092-8674(78)90058-2
  38. Liedholm P, Astedt B (1975): Fibrinolytic activity of the rat ovum, appearance during tubal passage and disappearance at implantation. Int J Fertil 20:24-26.
  39. Liu K, Brandstrom A, Liu YX, Ny T, Selstam G (1996): Coordinated expression of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 during corpus luteum formation and luteolysis in the adult pseudopregnant rat. Endocrinology 137:2126-2132. https://doi.org/10.1210/endo.137.5.8612557
  40. Liu YX (2007): Involvement of plasminogen activator and plasminogen activator inhibitor type 1 in spermatogenesis, sperm capacitation, and fertilization. Semin Thromb Hemost 33:29-40. https://doi.org/10.1055/s-2006-958459
  41. Liu YX, Cajande SB, Ny T, Kristen P, Hsueh AJW (1987): Gonadotropin regulation of tissue-type and urokinase-type plasminogen activators in rat granulosa and theca-interstitial cells during the periovulatory period. Mol Cell Endocrinol 54:221-229. https://doi.org/10.1016/0303-7207(87)90160-2
  42. Liu YX, Hu ZY, Liu K, Byrne S, Zou RJ, Ny T, d'Lacey C, Ockleford CD (1998): Localisation and distribution of tissue-type and urokinase-type plasminogen activators and their inhibitors type-1 and type-2 in human and rhesus monkey fetal membranes. J Anat 194:183-195.
  43. Liu YX, Ny T, Sarkar D, Loskutoff D, Hsueh AJW (1986): Identification and regulation of tissue plasminogen activator in rat cumulus-oocyte complexes. Endocrinology 119:1578-1587. https://doi.org/10.1210/endo-119-4-1578
  44. Liu YX, Peng XR, Ny T (1991): Tissue-specific and time-coordinated hormone regulation of plasminogen- activator-inhibitor type-1 and tissue-type plasminogen activator during gonadotrophin induced ovulation. Eur J Biochem 195:549-555. https://doi.org/10.1111/j.1432-1033.1991.tb15736.x
  45. Llanos M, Lui CW, Meizel S (1982): Studies of phospholipase A2 related to the hamster sperm acrosome reaction. J Exp Zool 221:107-117. https://doi.org/10.1002/jez.1402210114
  46. Martin O, Arias F (1982): Plasminogen activator production by trophoblast cells in vitro effect of steroid hormones and protein synthesis inhibitors. Am J Obstet Gynecol 142:402-409. https://doi.org/10.1016/S0002-9378(16)32380-8
  47. Menino AR, Williams JS (1987): Activation of plasminogen by the early bovine embryo. Biol Reprod 36:1289-1295. https://doi.org/10.1095/biolreprod36.5.1289
  48. Menshikov M, Plekhanova O, Cai H, Chalupsky K, Parfyonova Y, Bashtrikov P, Tkachuk V, Berk BC (2006): Urokinase plasminogen activator stimulates vascular smooth muscle cell proliferation via redox- dependent pathways. Arterioscler Thromb Vasc Biol 26:801-807. https://doi.org/10.1161/01.ATV.0000207277.27432.15
  49. Mignatti P, Rifkin DB (1993): Biology and biochemistry of proteinase in tumor invasion. Physiol Rev 73:161-195. https://doi.org/10.1152/physrev.1993.73.1.161
  50. Mintz B (1972): Implantation-initiating factor from mouse uterus. In: Moghissi KS, Hafez ESE (eds.), Biology of Fertilization and Implantation. Springfield: Thomas, pp. 343-356.
  51. Mullins DE, Bazer FW, Roberts RM (1980): Secretion of a progesterone induced inhibitor of plasminogen activator by the porcine uterus. Cell 20:865-872. https://doi.org/10.1016/0092-8674(80)90333-5
  52. Ny T, Bjersing L, Hsueh AJW, Loskutoff DJ (1985): Cultured granulosa cells produce two plasminogen activators and an anti activator, each regulated differently by gonadotropins. Endocrinology 116:1666-1668. https://doi.org/10.1210/endo-116-4-1666
  53. Ny T, Liu YX, Ohlsson M, Jone PBC, Hsueh AJW (1987): Regulation of tissue-type plasminogen activator activity and messenger RNA levels by gonadotropin- releasing hormone in cultured rat granulosa cells and cumulus-oocyte complexes. J Biol Chem 262:11790-11793.
  54. Olofsson B, Korpelainen E, Pepper MS, Mandriota SJ, Aase K, Kumar V, Gunji Y, Jeltsch MM, Shibuya M, Alitalo K, Eriksson U (1998): Vascular endothelial growth factor B (VEGF-B) binds to VEGF receptor-1 and regulates plasminogen activator activity in endothelial cells. Proc Natl Acad Sci USA 95:11709-11714. https://doi.org/10.1073/pnas.95.20.11709
  55. Pannell R, Grewich V (1987): Activation of plasminogen by single-chain urokinase or by two-chain urokinase- a demonstration that single chain urokinase has a low catalytic activity (pro-urokinase). Blood 69:22-26.
  56. Parr EL (1974): Histological examination of the rat ovarian follicle wall prior to ovulation. Biol Reprod 11:483-503. https://doi.org/10.1095/biolreprod11.5.483
  57. Peltz SW, Katzenellenbogen BS, Kneifel MA, Mangel WF (1983): Plasminogen activators in tissues of the immature and estrogen-stimulated rat uterus and in uterine luminal fluid: characterization and properties. Endocrinology 112:890-897. https://doi.org/10.1210/endo-112-3-890
  58. Ploplis VA, Carmeliet P, Vazirzadeh S, Van Vlaenderen I, Moons L, Plow EF, Collen D (1995): Effects of disruption of the plasminogen gene on thrombosis, growth and health in mice. Circulation 1: 2585-2593.
  59. Ploplis VA, French EL, Carmeliet P, Collen D, Plow EF (1998): Plasminogen deficiency differentially affects recruitment of inflammatory cell populations in mice. Blood 91:2005-2009.
  60. Plouet J, Moro F, Bertagnolli S, Coldeboeuf N, Mazarguil H, Clamens S, Bayard F (1997): Extracellular cleavage of the vascular endothelial growth factor 189-amino acid form by urokinase is required for its mitogenic effect. J Biol Chem 272:13390-13396. https://doi.org/10.1074/jbc.272.20.13390
  61. Rajput B, Degen S, Reich E, Walker E, Alexrod J, Eddy R, Shows T (1985): Chromosome locations of human tissue plasminogen activator and urokinase gene. Science 230:672-674. https://doi.org/10.1126/science.3840278
  62. Ranby M, Bersdorf N, Pohl G, Wallen P (1982): Isolation of two variants native one-chain tissue plasminogen activator. FEBS Lett 146:289-292. https://doi.org/10.1016/0014-5793(82)80936-8
  63. Reich E (1978): Activation of plasminogen: a general mechanism for producing localized extracellular proteolysis. In: Berlin RD, Hermann H, Lepow IH, Tanzer JM (eds.). In Molecular Basis of Biological Degradative Processes. Acad Press, Inc, NY. pp 155-169.
  64. Reich R, Miskin R, Tsafriri A (1985): Follicular plasminogen activator: Involvement in ovulation. Endocrinology 116:516-521. https://doi.org/10.1210/endo-116-2-516
  65. Rijken DC, Collen D (1981): Purification and characterization of the plasminogen activator secreted by human melanoma cells in culture. J Boil Chem 256:7035-7041.
  66. Rijken DC, Emeis J, Gerwig G (1985): On the composition and function of the carbohydrate meiotic of tissue-type plasminogen activator from human melanoma cells. Thromb Haemostas 54:788-791.
  67. Roldan-Olarte M, Jimenez-Diaz M, Miceli DC (2005): Plasminogen detection in oocytes and plasminogen activator activities in the porcine oviduct during the estrous cycle. Zygote 13:115-123. https://doi.org/10.1017/S0967199405003175
  68. Sa SJ, Rhee HH, Cheong HT, Yang BK, Park CK (2006): Effects of plasmin on sperm-oocyte interactions during in vitro fertilization in the pig. Anim Reprod Sci 95:273-282. https://doi.org/10.1016/j.anireprosci.2006.01.017
  69. Saksela O, Rifkin DB (1988): Cell-associated plasminogen activation: regulation and physiological functions. Annu Rev Cell Biol 4:93-126. https://doi.org/10.1146/annurev.cb.04.110188.000521
  70. Saksela O, Rifkin DB (1990): Release of basic fibroblast growth factor-heparan sulfate complexes from endothelial cells by plasminogen activator-mediated proteolytic activity. J Cell Biol 110:767-775. https://doi.org/10.1083/jcb.110.3.767
  71. Salustri A, Petrungaro S, De FM, Conti M, Siracusa G (1985): Effect of follicle-stimulating-hormone on cyclic adenosine monophosphate level and on meiotic maturation in mouse cumulus cell-enclosed oocytes cultured in vitro. Biol Reprod 33:797-802. https://doi.org/10.1095/biolreprod33.4.797
  72. Sappino AP, Huarte J, Belin D, Vassalli JD (1989): Plasminogen activators in tissue remodeling and invasion: mRNA localization in mouse ovaries and implanting embryos. J Cell Biol 109:2471-2479. https://doi.org/10.1083/jcb.109.5.2471
  73. Sherman MI (1980): Studies on the temporal correlation between secretion of plasminogen activator and stages of early mouse embryogenesis. Oncodev Biol Med 1:7-17.
  74. Sherman MI, Strickland S, Reich E (1976): Differentiation of early mouse embryonic and teratocarcinoma cells in vitro: plasminogen activator production. Cancer Res 36:4208-4216.
  75. Smokovitis A, Kokolis N, Alexaki-Tzivanidou E (1988): The plasminogen activator activity is markedly increased mainly at the area of the rupture of the follicular wall at the time of ovulation. Anim Reprod Sci 16:285-294. https://doi.org/10.1016/0378-4320(88)90022-X
  76. Smokovitis A, Kokolis N, Alexopoulos C, Alexaki E, Eleftheriou E (1987): Plasminogen activator activity, plasminogen activator inhibition and plasmin inhibition in spermatozoa and seminal plasma of man and various animal species. Effect of plasmin on sperm motility. Fibrinolysis 1:253-257. https://doi.org/10.1016/0268-9499(87)90045-2
  77. Smokovitis A, Kokolis N, Taitzoglou I, Rekkas C (1992): Plasminogen activator: the identification of an additional proteinase at the outer acrosomal membrane of human and boar spermatozoa. Int J Fertil 37:308-314.
  78. Sreicklad S, Beers WH (1976): Studies on the role of plasminogen activator in ovulation. In vitro response of granulosa cells to gonadotropins, cyclic nucleotides, and prostaglandins. J Biol Chem 251:5694-5702.
  79. Taitzoglou I, Kokolis N, Smokovitis A (1996): Release of plasminogen activator and plasminogen activator inhibitor from spermatozoa of man, bull, ram and boar during acrosome reaction. Mol Androl 8:187-197.
  80. Taitzoglou IA, Chapman DA, Killian GJ (2003): Induction of the acrosome reaction in bull spermatozoa with plasmin. Andrologia 35:112-116. https://doi.org/10.1046/j.1439-0272.2003.00541.x
  81. Taitzoglou IA, Chapman DA, Zervos IA, Killian GJ (2004): Effect of plasmin on movement charateristics of ejaculated bull spermatozoa. Theriogenology 62: 553-561. https://doi.org/10.1016/j.theriogenology.2003.11.016
  82. Talbot P, Chacon R (1981): Detection of modifications in the tail of capacitated guinea pig sperm using lectins. J Exp Zool 216:435-444. https://doi.org/10.1002/jez.1402160312
  83. Talbot P, Franklin LE (1978): Trypsinization increases lectin-induced agglutinability of uncapacitated guinea pig sperm. J Exp Zool 204:291-297. https://doi.org/10.1002/jez.1402040217
  84. Teesalu T, Blasi F, Talarico D (1996): Embryo implantation in mouse: fetomaternal coordination in the pattern of expression of uPA, uPAR, PAI-1 and _2MR/LRP genes. Mech Develop 56:103-116. https://doi.org/10.1016/0925-4773(96)00515-1
  85. Tsantarliotou MP, Zervos IA, Vatzias G, Billinis C, Taitzoglou IA, Kokolis NA (2005): Plasminogen activator activity in the porcine oviduct during the oestrous cycle. Theriogenology 64:1007-1015. https://doi.org/10.1016/j.theriogenology.2005.01.005
  86. Vassalli JD, Vaccino D, Belin D (1985): A cellular binding site for the Mr 55000 form of the human plasminogen activator, urokinase. J Cell Biol 100:86-92. https://doi.org/10.1083/jcb.100.1.86
  87. Verheijen J, Visse R, Wijnen J, Chang G, Kluft C, Mecrakhan P (1986): Assignment of the human tissue type plasminogen activator gene (PLAT) to chromosome 8. Human Genet 72:153-156.
  88. Wallen P, Pohl G, Bergsdorf N, Ranby M, Ny T, Jornall H (1983): Purification and characterization of a melanoma cell plasminogen activator. Eur J Biochem 132:681-686. https://doi.org/10.1111/j.1432-1033.1983.tb07418.x
  89. Yanagimachi R, Suzuki F (1985): A further study of lysolecithinmediated acrosome reaction of guinea pig spermatozoa. Gamete Res 11:29-40. https://doi.org/10.1002/mrd.1120110104
  90. Zhang T, Zhou HM, Liu YX (1997): Expression of plasminogen activator and inhibitor, urokinase receptor and inhibin subunits in rhesus monkey testes. Mol Hum Reprod 3:223-231. https://doi.org/10.1093/molehr/3.3.223
  91. Zheng P, Zou RJ, Liu YX (2001): Source of plasminogen activator in rhesus monkey semen and its possible role in sperm capacitation. Sheng Li Xue Bao 53:45-50.