ABSENCE OF THE HUMAN SPERM MEMBRANE ZONA ACCEPTOR AND ACROSOME REACTION
IN SUBFERTILE MEN WITH VARICOCELES.
1,2BR Gilbert, 3GW Cooper, 4I Hurley, 3S Benoff 1Department of Urology, The New York Hospital-Cornell Medical Center, New York , NY and The Department of 2Urology and 3The Division of Human Reproduction, The North Shore University Hospital-Cornell University Medical College, Manhasset, NY, 4Kemron Environmental Services, Huntington Station, NY
Objective: To determine whether the surface character of the spermatozoa from men with varicoceles differs from those of known fertile men.
Design: A prospective blinded, non-randomized (controlled) study evaluating two specific sperm membrane parameters in men with documented varicoceles, a prolonged period of subfertility and multiple failed impregnation attempts by intrauterine insemination.
Material and Methods: 7 subfertile men with varicoceles were evaluated. History and physical examination followed a standardized protocol. All had documentation of varicoceles by color flow scrotal ultrasound. At least two semen analyses were performed on each patient. Surface D-mannose binding sites (putative human zona acceptor lectins; Benoff et al., 1993, Fertil.Steril,in press) were identified by binding of a fluorescein isothiocyanate-conjugated mannosylated neoglycoprotein (Man-FITC-BSA) probe both at swim-up and after 18 and 72 hours of incubation in a capacitation medium. Acrosome status was assayed by double labeling, after ethanol permeabilization, with rhodamine-conjugated Pisum sativum agglutinin. Sperm from known fertile male served as a control.
Results: Known fertile sperm populations exhibit marked increases in the % of spermatozoa showing binding of Man-FITC-BSA and in spontaneous acrosome loss which are at plateau values by 18 hr and do not increase on extended incubation. In specimens from men with documented varicoceles, surface mannose-specific lectin expression did not significantly increase, even after prolonged incubation, nor was there an increase in spontaneous acrosome loss. Sperm from one varicocele patient was demembranated by vortexing, before and after capacitating incubations. His sperm were found to contain sub-plasma membrane stores of mannose lectins at all times. These stores were comparable to those seen only in fresh swim-up specimens from the normal control, thus indicating that there was a failure of trans-plasma membrane translocation on incubation. A similar analysis of sperm from a patient after varicocele ligation revealed that his sperm were essentially normal and that the carbohydrate binding sites of these sub-plasma membrane mannose lectins seen in fresh sperm externalized trans-membrane to the sperm surface after capacitating incubations.
Conclusions: As surface mannose lectin expression and spontaneous acrosome loss by sperm from fertile males are dependent on increased membrane fluidity during capacitation, these data suggest that the presence of a varicocele alters the character of the sperm membrane. This may be the result of the increased intrascrotal temperature found in men with varicoceles which may alter the sterol and lipid composition of the sperm membrane during spermatogenesis.