Şeref ERDOĞAN, Kerem Tuncay ÖZGÜNEN, Tuncay ÖZGÜNEN

Effects of $H^+ -K^+$ ATPase inhibitors (Omeprazole and lansoprazole) on fertilization-induced biolectrical potential changes in the egg of the frog, Rana cameranoi

Fertilizasyon, yumurtada $Ca^{2+}$ artışını ve kurbağa gibi bazı canlılarda alkalizasyonu tetiklemektedir. Ooplazmik $Ca^{2+}$ artışı Fertilizasyon Potansiyeli'ni (FP) başlatmakta, alkalizasyonun ise Ca2+ artışında permisif bir etkisi bulunmaktadır. Dolayısı ile yumurta içi pH regülasyonunun, hem ooplazmik $Ca^{2+}$ düzeyini, hem de $Ca^{2+}$ artışı ile tetiklenen olayları etkilemesi beklenebilir. Son yıllarda yapılan araştırmalarda farklı dokularda $H^+ -K^+$ ATPaz varlığının gösterilmesi, yumurtada da bu pompanın olabileceğini düşündürmektedir. Bu nedenle araştırmada, biyoelektrik potansiyellerinin kaydı ile kurbağa yumurtasında $H^+ -K^+$ ATPaz varlığının araştırılması amaçlanmıştır. Bunun için değişik yoğunluklarda (0.3, 0.6, 0.9 ve 1.2 mM) pompa inhibitörleri (omeprazol ve lansoprazol) içeren solüsyonlar uygulanan ortamlarda istirahat membran potansiyeli (IMP) kaydedilerek kurbağa yumurtaları döllendi ve FP parametrelerine inhibitörlerin etkileri incelenerek pompa varlığı hakkında bilgi edinilmesine çalışıldı. Kurbağa yumurtasında IMP ve FP parametrelerini omeprazol yalnız l .2 mM yoğunluğunda anlamlı olarak etkilerken, lansoprazolün 0.6 mM ve üstündeki yoğunluklarda anlamlı etkileri vardı. Her iki pornpa inhibitörü etkisinin benzer yönde olduğu bulundu. Sonuç olarak, kurbağa yumurtasında fertilizasyon ile tetiklenen potansiyel değişiklikler üzerine her iki pompa inhibitörünün de benzer etkilerde bulunması, kurbağa yumurta membranında $H^+ -K^+$ ATPaz olabileceğini gösterebilir. Böylece, bu pompanın kurbağa yumurtasında fertilizasyonla gözlenen alkalizasyonun gelişmesine katkıda bulunabileceği düşünülebilir.

Rana cameranoi türü kurbağa yumurtasında fertilizasyonda ortaya çıkan biyoelektrik potansiyel değişikliklere $H^+ -K^+$ ATPaz inhibtörlerinin (Omeprazol ve lansoprazol) etkileri

Fertilization triggers Ca increase and alkalization in the eggs of some species such as the frog. Ooplasmic Ca increase triggers fertilization potential (FP), and alkalization can have a permissive effect in $Ca^{2+}$ increase. It can be expected that pH regulation in the egg can affect both ooplasmic $Ca^{2+}$ levels and the events triggered by increasing $Ca^{2+}$. The evidence of the possibility of $H^+ -K^+$ ATPase in different tissues in recent studies prompted us to wonder about the probability of the existence of this pump in the egg. Therefore, we decided to investigate the presence of $H^+ -K^+$ ATPase by bioelectrical potential recordings in frog eggs. Thus, frog eggs were inseminated while the resting membrane potential (RMP) in the solution containing different concentrations (0.3, 0.6, 0.9 and 1.2 mM) of pump inhibitors (omeprazole and lansoprazole) was recorded. Evidence of $H^+ -K^+$ ATPase was sought from the effects of these pump inhibitors on FP variables. While omeprazole had a significant effect on RMP and FP variables at a 1.2 mM concentration alone, lansoprazole had significant effects at concentrations higher than 0.6 mM in the frog eggs. It was determined that the effects of the 2 inhibitors were similar. In conclusion, H+-K+ ATPase may be present in frog eggs due to the similar effects of both pump inhibitors on the potential change triggered by fertilization. Thus, this pump might have a function in alkalization triggered by fertilization in the frog egg.

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1. Jaffe; LA.: Electrical regulation of sperm-egg fusion. Ann. Rev. Physiol. 1986; 48: 191-200.
2. Erdoğan, Ş., Loğoğlu, G., Özgünen, T;: The importance of bioelectrical potentials at fertilization. Ann. Med. Sci. 1999; 8: 58-62.
3. Grandin, N., Charbonneau, M.: Intracellular pH and the increase in protein synthesis accompanying activation of Xenopus eggs. Bio. Cell. 1989:67:321-330.
4. Grandin, N., Charbonneau, M.: The increase in intracellular pH associated with Xenopus egg activation is a $Ca^{2+}$ -dependent wave. J-Cell. Scien. 1992; 101:55-67.
5. Philips, K.P., Baltz, J.M.: Intracellular pH regulation by HCO3/CI exchange is activated during early mouse zygote development. Dev. Biol. 1999; 208: 392-405.
6. Jaffe, LA., Schlichter, L.C.: Fertilization induced ionic conductance in eggs of the frog, Rana pipiens. J. Physiol. 1985; 358:299-319.
7. Ben-Yosef, D., Oron, Y., Shalgi, R.: Intracellular pH of rat eggs is not affected by fertilization and the resulting calcium oscillations. Biol. Reprod. 1996; 55: 461-468.
8. Charnonneau, M., Webb, D.J.: Multiple activation currents can be evoked in Xenopus laevis eggs when cortical granule exocytosis is inhibited by weak bases. Pflügers Arch. 1986; 407: 370-376.
9. Georgiou, P., House, C.R., McNiven, A.I., Yoshida, S.: On the mechanism of a pH-induced rise in membrane potassium conductance in hamster eggs. J. Physiol. 1988; 402: 121-138.
10. Erdoğan, Ş., Loğoğlu, L, Özgünen, K.T., Özgünen T.: Effects of pH on the genesis of membrane potential changes at fertilization, in the egg of the frog Rana cameranoi. Turk. J. Biol. 2000; 24: 725-736.
11. McCabe, R.D., Yung, D.B.: Evidence of a $H^+-K^+$ ATPase in vascular smooth muscle cells. Am. J, Physiol. 1992; 262: H1955-1958.
12. Rhoden, K.J., Tallini, G., Douglas, J.S.: $H^+-K^+$ ATPase inhibitors cause relaxation of guinea pig and human airway smooth muscle in vitro. J. Pharmacol. Exp. Ther. 1996; 276: 897-903.
13. Ikuma, M., Binder, H.J., Geibel, J.: Role of apical H-K exchange and basolateral K channel in the regulation of intracellular pH in rat distal colon crypt cells. J. Memb. Biol. 1998; 166: 205-212.
14. Rajendran, V.M., Singh, S.K., Geibel, J., Binder, H.J.: Differential localization of colonic $H^+-K^+$ -ATPase isoforms in surface and crypt cells. Am. J. Physiol. (Gastrointest. Liver Physiol.). 1998; 37: G424-429.
15. Levin, M., Thorlin, T., Robinson, K.R., Nogi, T., Mercola, M.: Asymmetries in H+/K+-ATPase and cell membrane potentials comprise a very early step in left-right patterning. Cell. 2002, 111: 77-89.
16. Başoğlu, M., Özeti, N.: The amphibians of Turkey (Taxonomic list, distribution, key for identification) Ege University İzmir, (1973), p. 104 (in Turkish). 17. Perkins, K.W., Whitten, R.H.: Reptiles and Amphibians: Care and Culture, Carolina Biological Supply Company, USA, 1981; p.9-11
18. Rugh, R.: Experimental embryology techniques and procedures Burgess Publishing Company, USA, 1962; p.93.
19. Erdoğan, Ş., Loğoğlu, G., Özgünen, T.: The ionic basis of membrane potential changes from before fertilization throuqh the first cleavage in the egg of the frog, Rana cameranoi. Gen Physiol. Biophys. 1996; 15: 371-387.
20. Sümbüloğlu, K., Sümbüloğlu, V.: Biostatistics (8lh edition) Hatiboğlu Publishing, Ankara (1998) (in Turkish).
21. Gianaroli, L., Tosti, E., Magli, C, Laccarino, M., Ferraretti, A.P Dale, B.: Fertilization current in the human oocyte. Mol. Dev. 1994; 38: 209-214.
22. Igusa, Y., Miyazaki, S., Yamashita, N.: Periodic hyperpolarizing responses in hamster and mouse eggs fertilized with mouse sperm. J. Physiol. 1983; 340: 633-647.
23. Stanton, B.A.: The Kidney, In Physiology eds: Bern, R.M., Levy M.N. (4th edition) Mosby-Year Book, USA, 1998; p.751.
24. Kutchai, H.C.: Cellular Physiology, In Physiology eds: Bern, R.M., Levy, M.N., 4th edition Mosby-Year Book, USA, 1998; p. 27.