Daily patterns of plasma atrial natriuretic peptide, serum osmolality and haematocrit in the rat.
The present study documents daily rhythms of plasma atrial natriuretic peptide, serum osmolality and haematocrit in the rat. One-hundred and twenty-five Sprague-Dawley rats were used. They were bred under a cycle of 12 h light/12 h dark starting at 07.00 h. Fifty-three rats were decapitated between 09.00 and 16.00 h (study I) and 72 rats in groups of six were decapitated at 2-h intervals for a period of 24 h (study II). In study I, plasma atrial natriuretic peptide was 156 +/- 11 pg mg-1 (mean +/- SEM). In study II, atrial natriuretic peptide was at a control level from 08.00 to 18.00 h and then began to increase. At 22.00 h, atrial natriuretic peptide was 420 +/- 105 pg ml-1, which was significantly higher than at 08.00 h (P less than 0.05). The serum osmolality was over 300 mosmol kg-1 during the day. The highest mean osmolalities (315, 317, 312 mosmol kg-1) were found from 18.00 to 22.00 h. These were significantly different (P less than 0.05) from other groups during the day. The haematocrit was highest at 14.00 h (49.5 +/- 0.7%) and lowest at 24.00 h (43.6 +/- 0.8%) (P less than 0.05). In conclusion, we have shown that there are significant daily rhythms of plasma atrial natriuretic peptide, serum osmolality and haematocrit during a 24-h period and 12 h light/12 h dark cycle in the rat.
Kanervo
A
A
Department of Physiology, University of Oulu, Finland.
Arjamaa
O
O
Vuolteenaho
O
O
Leppäluoto
J
J
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood*; D002940:Circadian Rhythm / Q000502:physiology*; D006400:Hematocrit; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D011919:Rats, Inbred Strains
D009320:Atrial Natriuretic Factor