For more than 40 years, it was assumed that the life cycle of sperm in the adult male was 60 to 70 days - from origin to ejaculation.
Now findings from a research study suggest the actual time may be as low as 42 days, contradicting previous beliefs.
"With a more concise and accurate timeline to work with, we can potentially change the way male infertility is treated," said Paul Turek, MD, the study's lead researcher, who is associate professor of urology and a male infertility expert at UCSF Medical Center.
"This breakthrough might aid in how drugs for infertility and male birth control are studied, and help us better understand the effect of drugs and surgical treatments on male infertility," he added. "We used to wait a couple of months to assess the effects of male treatments, but this suggests we should start looking for changes earlier. This kind of information can be very valuable in cases of fertility with advanced maternal age, where every month of potential fertility counts for the couple."
Turek also noted that the sperm analysis technique developed in the study "might be able to delineate whether men with no sperm in the ejaculate have blockage or not" and avoid unnecessary diagnostic surgery.
Results from the study are reported in the January 2006 issue of Journal of Urology, published by the American Urological Association.
Researchers used a noninvasive technique to measure cell division and cell turnover in sperm after study participants ingested enriched "heavy water," a type of water with twice the mass of ordinary hydrogen. Over the course of three weeks, a total of 11 healthy adult males in the study ingested heavy water. Semen samples were collected every two weeks for up to 90 days. DNA sperm cell samples were labeled and quantified, enabling researchers to determine the percentage of new sperm produced during intervals of measurement.
Study findings showed a range of 42 to 76 days from the time of sperm production to ejaculation in normal men.
"In 1963, there was one very novel study that was quite invasive in nature, in which study participants were subjected to radiation exposure or injections into the testes for study," said Turek. "That method would never be replicated today. This new process is much less invasive and quite safe, with equal or better scientific and clinical value. In addition to informing us about the timeline of sperm production, it has given us more information about how long sperm is actually 'stored' in the system before ejaculation."
The sperm analysis technique used in the study was developed by KineMed, Inc., of Emeryville, Calif., which also funded the study.
Along with Turek, study researchers were Lisa Misell, PhD, director of clinical research, KineMed; Daniel Holochwost, MS, staff research associate, KineMed; Drina Boban, MPH, Division of Endocrinology and Metabolism, UCSF; Noelle Wingate-Santi, BS, staff research associate, KineMed; Shai Shefi, clinical fellow in urology, UCSF; and Marc Hellerstein, MD, PhD, Division of Endocrinology and Metabolism at UCSF and Department of Nutritional Sciences and Toxicology at UC Berkeley.
Source: Nancy Chan