THE crocodile in Peter Pan had a ticking belly. We鈥檝e got one too, except our ticking comes from the adrenal glands above our kidneys and not from a swallowed alarm clock.
The mammalian body clock was thought to be set exclusively by a part of the hypothalamus in the brain called the suprachiasmatic nucleus (SCN). Now Henryk Urbanski and his colleagues at the Oregon National Primate Research Center in Beaverton, Oregon, have discovered a second clock 鈥� in the adrenal glands.
Urbanski and his team discovered rhythmic 24-hour fluctuations in gene activity in at least 322 genes in the adrenal glands of macaques, including six vital for clock activity in the SCN. Urbanski says the adrenal clock probably plays a key role in releasing mood-altering hormones at key times. The stress hormone cortisol, for example, usually peaks in the morning to provide vigour, and troughs in the evening to promote sleepiness (Molecular Endocrinology, vol 20, p 1164).
Advertisement
Urbanski says that the SCN is probably the master clock, because it receives information on light levels directly from the retina. 鈥淲e don鈥檛 know how the adrenal clock is being synchronised with the environment,鈥� he says. The discovery could yield better treatments for jet lag.
