A protein that determines how much urine can be stored in the bladder seems to be controlled by the body’s internal clock, suggests research published in Nature Communications this week. The discovery of this novel regulatory mechanism may explain why bladder capacity increases during the night and provides a new hypothesis as to why some people, such as the elderly or small children, show unusual urination behaviours.
The reasons why humans and rodents normally store more urine in the bladder when fast asleep than when awake are not fully understood. Osamu Ogawa and his team measured the bladder capacity of mice subjected to varying cycles of light and darkness, and found that bladder capacity oscillated in synchrony with the body’s internal clock. Further molecular analyses revealed that the production of the protein connexin43 in bladder muscle cells was regulated by molecular components of the internal clock and peaked during the night. Accordingly, mice which produce less connexin43 urinated more frequently during the night − similar to people with an overactive bladder.
This finding warrants the investigation of possible disturbances in the body’s internal clock in patients with increased urination at night. The researchers caution, however, that other factors−such as impaired cortical arousal levels in the brain and urine production in the kidneys−may also affect bladder capacity.