title: Kinetics of protein tyrosine phosphorylation in sperm selected by binding to homologous and heterologous oviductal explants: how specific is the regulation by the oviduct?
abstract: Essential steps of the capacitation process take place in the oviductal isthmus. A crucial step in the process of capacitation is the phosphorylation of membrane proteins. The aims of this work were (1) to study the effect of dog sperm binding to oviductal epithelium on tyrosine phosphorylation and (2) to investigate the specificity of regulation of molecular changes by the oviduct of different species by comparing the numbers of canine sperm bound to heterologous (porcine) and homologous epithelium, and the kinetics of tyrosine phosphorylation. Semen was collected from four healthy dogs and washed through a Percoll gradient. Explants, small pieces of epithelium, were cut from porcine and estrous bitch oviducts. During 6 h of coincubation in Tyrode medium, the numbers of bound sperm were counted by microvideographic observation, and the state of tyrosine phosphorylation was determined immunocytochemically after 3, 30, 90, 180 and 360 min. Canine sperm bound in similar numbers to homologous and heterologous explants. Increasing tyrosine phosphorylation of tail proteins and subsequent phosphorylation of sperm head proteins were observed. Binding occurred mainly in sperm with non-phosphorylated heads (approximately 2% phosphorylated), while higher proportions of head-phosphorylated cells were found in unbound populations (approximately 40-60%;P<0.05). The head phosphorylation progressed significantly during incubation in unbound spermatozoa (P<0.05), while it was suppressed in bound suspensions. The rate of tyrosine phosphorylation of sperm tail proteins was higher in cells bound to explants than in unbound cells or in those incubated in control medium. There were no significant differences with respect to the kinetics of tyrosine phosphorylation between the two coincubation systems. These observations support the hypothesis that spermatozoa with non-phosphorylated heads preferentially attach to epithelial cells. Tyrosine phosphorylation of sperm head proteins and capacitation are delayed in spermatozoa in close contact with oviductal epithelium. This mechanism appears to be species-independent, as sperm bound similarly to pig and dog oviduct explants, and similar phosphorylation kinetics were observed in both types of tissue.
authors.affiliation: Institute for Reproductive Medicine, School of Veterinary Medicine Hannover, Bünteweg 15, 30559 Hannover, Germany.
authors.forename: A M
authors.initials: AM
authors.lastname: Petrunkina
authors.forename: K
authors.initials: K
authors.lastname: Simon
authors.forename: A-R
authors.initials: AR
authors.lastname: Günzel-Apel
authors.forename: E
authors.initials: E
authors.lastname: Töpfer-Petersen
mesh_terms: D000818:Animals; D004285:Dogs; D005187:Fallopian Tubes / Q000502:physiology*; D005260:Female; D007700:Kinetics; D008297:Male; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D013045:Species Specificity; D013075:Sperm Capacitation; D013077:Sperm Head / Q000737:chemistry; D013082:Sperm Tail / Q000737:chemistry; D013094:Spermatozoa / Q000737:chemistry / Q000378:metabolism*; D013552:Swine; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D011506:Proteins; D014443:Tyrosine