Details

Autor(en) / Beteiligte

• Tunçtan, Bahar
• Weigl, Yuval
• Dotan, Aviva
• Peleg, Leah
• Zengil, Hakan
• Ashkenazi, Israel
• Abacıoğlu, Nurettin

Titel

Circadian variation of nitric oxide synthase activity in mouse tissue

Ist Teil von

• Chronobiology international, 2002-01, Vol.19 (2), p.393-404

Ort / Verlag

Monticello, NY: Taylor & Francis

Erscheinungsjahr

2002

Quelle

Taylor & Francis

Beschreibungen/Notizen

• Endogenous nitric oxide (NO) is an important mediator in the processes that control biological clocks and circadian rhythms. The present study was designed to elucidate if NO synthase (NOS) activity in the brain, kidney, testis, aorta, and lungs and plasma NO x levels in mice are controlled by an endogenous circadian pacemaker. Male BALB/c mice were exposed to two different lighting regimens of either light-dark 14:10 (LD) or continuous lighting (LL). At nine different equidistant time points (commencing at 09:00h) blood samples and tissues were taken from mice. The plasma and tissue homogenates were used to measure the levels of NO 2 + NO 3 − (NO x ) and total protein. The NO x concentrations were determined by a commercial nitric oxide synthase assay kit, and protein content was assessed in each homogenate tissue sample by the Lowry method. Nitric oxide synthase activity was calculated as pmol/mg protein/h. The resulting patterns were analyzed by the single cosinor method for pre-adjusted periods and by curve-fitting programs to elucidate compound rhythmicity. The NOS activity in kidneys of mice exposed to LD exhibited a circadian rhythm, but no rhythmicity was detected in mice exposed to LL. Aortic NOS activity displayed 24h rhythmicity only in LL. Brain, testis, and lung NOS activity and plasma NO x levels displayed 24h rhythms both in LD and LL. Acrophase values of NOS activity in brain, kidney, testis, and lungs were at midnight corresponding to their behavioral activities. Compound rhythms were also detected in many of the examined patterns. The findings suggest that NOS activity in mouse brain, aorta, lung, and testis are regulated by an endogenous clock, while in kidney the rhythm in NOS activity is synchronized by the exogenous signals.