Researchers observed a protein, known as "PROKR1", raised the risk of an egg implanting outside the womb.
Women who smoked and developed an ectopic pregnancy had two times more PROKR1 in their fallopian tubes as women who did not smoke, and had an earlier healthy pregnancy.
Also, they have demonstrated low or absent levels of expression for EG-VEGF receptors (PROKR1 and PROKR2) in ectopic endometriotic tissues.
EG-VEGF (also known as prokineticin-1) and prokineticin-2 act on 2 receptors, namely, PROKR1 and PROKR2 [14,25,26].
Both agents act on 2 types of receptors, known in scientific literature as PROKR1 and PROKR2 .
Several studies demonstrated an increased expression of EG-VEGF receptors, PROKR1 and PROKR2, in the placenta during the first trimester of pregnancy [4, 5, 28].
It has been concluded that PROKR1 mediates the angiogenic effects of EG-VEGF and that PROKR2 mediates EG-VEGF action on cell permeability.
Researchers found that female smokers who have had an ectopic pregnancy have raised levels of a harmful protein - PROKR1
- in their fallopian tubes, caused by a chemical in smoke.
The protein, called PROKR1, raised the risk of an egg implanting outside the womb.
PROKR1 allows pregnancies to implant correctly inside the womb, but its presence in the Fallopian tubes is believed to increase the risks of this happening outside the womb.
The study found that women who smoked and developed an ectopic pregnancy had twice as much PROKR1 in their Fallopian tubes as women who did not smoke and had previously had a healthy pregnancy.
Prokineticins can bind to two different G protein-coupled receptors, PROKR1
and PROKR2, sharing about 85% sequence identity.