HEAT-INDUCED HYPERACTIVATION

Purpose: The objectives of this study were (1) to determine the sperm hyperactivation and related kinematic parameters at 40 degrees C after using four sperm wash procedures and (2) to correlate the heat-induce d hyperactivation data with cases of clinical pregnancies from either artificial insemination or standard iii vitro fertilization (IVF). Met hods: Semen samples (n = 51) were collected by ejaculation, and semen analyses were carried out to determine the pretreatment data, Sperm ki nematic measurements were performed using the Hamilton Thorn HTM-C com puter-aided sperm analyzer. Hyperactivation was determined using the s ort module on rite HTM-C. Membrane integrity was assessed using the hy poosmotic sperm swelling procedure. Sperm morphology and acrosomal sta tus were also determined using the Spermac stain. Each semen specimen was divided and processed through either the swim-up wash, the I-h tes t-yolk buffer (TYB) wash, the 1 mg/ml pentoxifylline simulant procedur e, or the two-layer 90:47% gradient colloidal solution procedure. The washed sperm were incubated at 25 or at 40 degrees C for 4 hr: After i ncubation, kinematic parameters were assessed for the posttreatment da ta. Semen specimens were obtained on different occasions Sor artificia l insemination or standard IVF. Data from intracytoplasmic sperm injec tion cases were not included ro avoid confounding factors. Live births and/or pregnancies with fetal heart-beat examined by ultrasound were considered clinical pregnancies. Results: Heat-induced hyperactive mot ility was significantly higher in sperm of the male partner of pregnan t (n = 7) patients compared with nonpregnant (n = 44) patients (mean /- SE, 10.0 +/- 3.3 versus 5.5 +/- 0.8%) after TYB processing followed by 4 hr of incubation at 40 degrees C. This was also observed after c olloid (Percoll) processing (11.6 +/- 4.6 versus 5.8 +/- 0.8%), There were no differences in hyperactivation after 4 hr at 23 degrees C betw een pregnant and nonpregnant cases. Parameters such as count, volume, motility viability, and acrosontal status were not different for the g roups. However the percentage of sperm with normal morphology (WHO cla ssification) was twice as high in the pregnant group versus the nonpre gnant group. Conclusions: Heat-induced hyperactivation was associated with fertile sperm and was predictive of pregnancy obtained after arti ficial insemination or NF: The association was evident only after TYB or Percoll sperm processing, The study could not confirm the finding o f significant decreases in motility after heat treatment of sperm deri ved from infertile males, The mechanism for heat-induced hyperactivati on did not involve membrane integrity or the sperm acrosome, although art involvement of hear shock proteins was postulated, Interestingly, there were no pregnancies when sperm did not exhibit heat-induced hype ractivation.