822 



PERIODIC FUNCTIONS IN MAMMALS 



By contrast to cortical adrenal mitoses, skin mitoses are roughly in 

 phase with the eosinophil rhythm. 



In the course of the experiment partly summarized in Fig. 13, pools 

 of serum from the same mice were obtained for corticosterone deter- 

 mination carried out in different laboratories (Halberg, Peterson, and 

 Silber, in press), as well as more recently in Minnesota (Fig. 14). 



pg (poir) 



.024 



.020 



.016 - 



(of 24- hr. X) 



130 



100 - 



70 



"corticosterone" 



in 

 SERUM 

 ond 



ADRENAL: 



"corticosterone" parenchymal 



MITOSES 



M {%) 



20 



06:00 12;00 I8:00 24:00 06:00 

 TIME 



- 10 



(of 24-hr. X) 

 150 



100 



50 



Fig. 14. Twenty-four-hour rhythms of corticosterone in mouse blood 

 and adrenal in relation to mitoses in glandular parenchyma. 



Blood levels of corticosterone in mice were found to exhibit 24-hr 

 periodicity, and the peak blood levels were reliably reproduced at 

 about 16:00, with light daily from 06:00 to 18:00. What seems more 

 important. Fig. 14 further reveals periodic changes in the hormone 

 content of the adrenal cortex itself, and the timing of the adrenal corti- 

 costerone rhythm supports the suggestion that mitotic activity in the 

 adrenal cortex proceeds when the hormone is released from the gland. 



