Circadian and ultradian (12 h) rhythms of hepatic thiosulfate sulfurtransferase (rhodanese) activity in mice during the first two months of life.

Thiosulfate sulfurtransferase (TST) is an important 'enzyme of protection,' that accelerates the detoxification of cyanide, converting it into thiocyanate. The TST physiological rhythm was investigated at wks 2, 4, and 8 of post-natal development (PND) in the mouse. The results revealed a statistically significant gender-related difference, with the highest activity in females, at all the documented PND stages. In the second week of PND (pre-weaning time), the circadian rhythm of the enzyme activity was associated with ultradian components. The prominent circadian rhythm (tau=24 h) peaked at the beginning of the light span, more precisely approximately 3 HALO (Hours After Light Onset). A week after weaning (wk 4 of PND), an impairment of the rhythm, with the peak shifted toward the second half of photophase, was recorded. Four to 6 wks later, about wk 8 of PND, the circadian rhythm pattern was stabilized, with its peak then located at the beginning of the dark span (13 HALO). The obtained results showed a 12 h phase-shift of the circadian TST peak time during PND, suggesting that the rhythm stabilization is age-dependent.