Seasonal variation of endothelin-1, angiotensin II, and plasma catecholamines and their relation to outside temperature.

Circannual rhythmicity in plasma catecholamines is well known, but no chronobiologic data are available on endothelin-1 and angiotensin II. This study was designed to investigate in healthy human subjects whether endothelin-1 and angiotensin II exhibit seasonal variations. Furthermore, we assessed the relation of both variables to plasma catecholamines, to environmental temperature, and to relative humidity in northern Germany, a region of a temperate climate.