Changes in the Activities of Plasma Acid and Alkaline Phosphatases 183 



pattern of the changes in the activities of these enzymes has already been reported 

 (Taylor et ai, 1965), and these changes are shown in Fig. 1. 



/^c//c changes in the levels of plosmo Acid and Alkaline phosphatases 

 in relation to egg shell calcification 



3n pre 

 the 



S 10 /5 JO 



Hours after start of shell calcificalion 



changes in the levels of plasma acid and alkaline phosphatases in 

 ss. The points represent mean corrected values for each particular 

 umber of individual values from which the means are derived are j 



elation to the eggshell calci- 

 tage of shell formation and 

 en below each point 



Experimental 



Ten laying hens were bled at the following times: 



Sample A — at the time the egg entered the shell gland (determined by regular 

 palpation). 



Sample B — 4 hours after A, when maximum alkaline phosphatase activity was 

 expected. 



Sample C — 18 hours after A, when maximum acid phosphatase activity was 

 expected. 



Sample D — 2 hours after oviposition. 



Samples A, B and C were assayed for alkaline phosphatase and samples A, C and 

 D for acid phosphatase. 



The acid phosphatase was determined by the method of Bell and Siller (1962) 

 using 0.2 M acetate buffer at pH 4.9 and the alkaline phosphatase according to Bell 

 (1960). Both methods employ disodium p-nitrophenyl phosphate as substrate and the 

 units of activity were calculated in terms of //M substrate hydrolysed per minute 

 per litre plasma. 



Results 



The activities of plasma acid and alkaline phosphatase obtained for the individual 

 birds at the 3 stages of the laying cycle are given in Tables 1 and 2 respectively. The 

 marked increase observed in the acid phosphatase values from the time the egg 

 entered the shell gland (A samples) to the time 18 hours later when shell calcification 



