MARIJUANA'S EFFECT ON EARLY-STAGE EMBRYOS

BOB EDWARDS, host:

Scientists have shown that marijuanalike compounds have an effect on
embryos. When scientists exposed mouse embryos to different levels of such
compounds, it affected the way the embryos developed. Those results appear
in the current issue of the Proceedings of the National Academy of
Sciences. It could lead to new ways to improve human fertility. NPR's Joe
Palca reports.

JOE PALCA reporting:

The story of how researchers found the relationship between marijuana and
the early embryo has a curious start. During the war in Vietnam, scientists
noticed that some male fighters who smoked a lot of marijuana started
growing breasts. The scientists thought they knew the reason why.

Mr. SUDHANSU DEY (Reproductive Biologist, Vanderbilt University Medical
Center, Nashville): They thought that marijuana products probably behaved
like estrogen.

PALCA: Sadhansu Dey is a reproductive biologist at Vanderbilt University
Medical Center in Nashville. Dey says it's well known that estrogen can
cause men's breasts to grow but it wasn't clear why a product from a
cannabis plant would do that, too. At the time, Dey was focusing on how
estrogen affected embryos.

Mr. DEY: So I was very intrigued about that, that way that cannabinite
products could behave like estrogen.

PALCA: Some of these cannabinoid products are actually produced in the body
and it was these Dey was most interested in. He spent years studying mice
trying to see if there was any relationship between these natural
cannabinoids and estrogen and couldn't find any. For a while, he was
stumped. He thought for sure that estrogen was crucial for controlling
early embryo development. But then he decided to see whether the
cannabinoids the mice were producing themselves were having their own
direct effect on the embryo. Dey says they were.

Mr. DEY: What we found, that at low dose, these embryos become
activated. At higher doses, it inhibits embryonic growth in vitro.

PALCA: In other words, these cannabinoids are sending chemical signals to
the developing embryo, telling it when to grow.

Herbert Schuel is a reproductive biologist at the University of Buffalo.

Mr. HERBERT SCHUEL (Reproductive Biologist, University of Buffalo): The
consequence of that is to regulate how the embryo is developing so that it
can implant properly into the lining of the uterus and go on to develop
into a little baby mouse.

PALCA: The idea that the body is producing its own marijuanalike compounds
that are controlling the steps of development will take some getting used
to. Fuller Bazer is a reproductive biologist at Texas A&M University.

Mr. FULLER BAZER (Reproductive Biologist, Texas A&M University): I think
the surprising thing is that we usually associate cannabinoids, you know,
with marijuana and that sort of thing, you know, as being high from a plant
source rather than being produced in significant amounts by mammalian tissues.

PALCA: But cannabinoids from plant sources aren't completely out of the
picture. Sudhansu Dey says it's likely that cannabinoids taken into the
body by smoking marijuana will also send signals to the developing embryo.

Mr. DEY: If a woman is consuming regularly cannabinoid products, that can
also have an added burden to the system and may, you know, interfere with
pregnancy. We don't know for sure but my studies suggest that.

PALCA: On a brighter note, Dey says understanding more about how natural
cannabinoids work may help women who are having difficulties getting
pregnant. Joe Palca, NPR News, Washington.