Daily rhythmic variations in blood coagulation times in rats

✍ Scribed by Scheving, Lawrence E. ;Pauly, John E.

• Book ID: 102745076
• Publisher: John Wiley and Sons
• Year: 1967
• Tongue: English
• Weight: 658 KB
• Volume: 157
• Category: Article
• ISSN: 0003-276X
• DOI: 10.1002/ar.1091570411

✦ Synopsis

With all other environmental factors rigidly standardized, normal Sprague-Dawley rats were maintained under the following schedules: (1) 12 hours of artificial light 0600 to 1800 alternating with 12 hours of darkness-LD; (2) reversal of the first-DL; (3) constant darkness-DD, and (4) constant illumination-ll.

After the animals had been under a specific lighting regimen for at least three weeks, blood coagulation times were determined on separate groups of 8 to 16 animals at bi-hourly intervals during a %-hour period. Signiiicant daily fluctuations or rhythms in coagulation times under all lighting conditions were found by plotting each of the bi-hourly mean values as a function of time. The temporal phasing of all rhythms in LD, DL, LL and DD were similar. T h e major changes found in the different lighting schedules involved overall magnitude, e.g., the overall 24-hour mean coagulation time for rats maintained in LL was 21% greater than for rats maintained in DD. Although total adrenalectomy or adrenal medullectomy did not abolish the characteristic LD rhythm, there was about a 100% decrease in the mean %-hour