Estrogen may contribute to the development of Raynaud’s phenomenon in women, according to a study examining the relationship between palm blood flow and the hormone in mice. The findings might explain why Raynaud’s is more common in women of childbearing age.
The study noted that reduced blood flow was mediated by estrogen’s effects on cell surface receptors.
The study, “G-protein coupled estrogen receptor-mediated non-genomic facilitatory effect of estrogen on cooling-induced reduction of skin blood flow in mice,” was published in the European Journal of Pharmacology.
The reduced blood flow in hands and feet when people are exposed to cold is controlled both by nerve signals by what is known as the sympathetic nervous system, and by local processes constricting blood vessels.
Researchers at the University of Shizuoka in Japan contended that estrogen may be involved in boosting the local responses to cold. The most well-known effects of the female sex hormone involve actions directly on cells’ DNA, where it binds to genes to control their activation. But the hormone also can act on receptors on the cell surface.
To explore only the actions of estrogen that are not mediated by gene effects, the research team set up an elaborate experiment. To reduce the impact of natural hormonal fluctuations, they used female mice that lacked ovaries. They then treated the mice with a compound that blocked the signaling from the sympathetic nervous system.
The mice, which were put to sleep, then had a foot exposed to temperatures that dropped from 25℃ (77℉) to 10℃ (50℉) in five-degree increments.
The cooling reduced blood flow as expected, and when mice were injected with estrogen, the effect of the cold temperature was boosted. The highest hormonal concentrations reduced blood flow the most.
But when researchers blocked a receptor involved in the local blood vessel constriction response, estrogen no longer increased the effect of the cold temperature.
To examine if it was estrogen’s actions on DNA or external cell receptors that was behind the boosting effects, researchers treated the mice with a compound that stimulated one of the receptors estrogen is known to bind. Stimulating the receptor also increased the reduction in blood flow. Likewise, blocking this receptor prevented the hormone from reducing the blood flow.
Although the study does not exclude the possibility that estrogen also impacts Raynaud’s processes through its actions on other genes, the study’s experiments show that the hormone likely contributes to the condition by affecting local molecular events that constrict blood vessels.