Efek preparasi spermatozoa terhadap aktivitas spesifik Na+,K+-ATPase dan Ca2+-AT Pase-atpase serta distribusi protein Na+,K+-ATPase α4 dan plasma membrane Ca2+-ATPase 4 = The effect of sperm preparation on na k atpase and ca2 atpase specific activities and distribution of na k atpase 4 and plasma membrane ca2 atpase 4 isoforms