Diurnal and menstrual cycle variations in serum vitamin B-12 and folacin activity in baboons

Serum levels of vitamin B-12 and folacin were determined every 6 hours over a 24-hour period in five baboons and every other day throughout complete menstrual cycles in seven baboons. All baboons were normally cycling females exhibiting serum estrogen, progestin, and luteinizing hormone levels during the follicular, ovulatory and, luteal phases, respectively, of their menstrual cycles of 217.9 plus or minus 115.6, 420.3 plus or minus 113.9, 207.3 plus or minus 88.6 pg/ml; 1.71 plus or minus 0.84, 2.72 plus or minus 1.50, 5.92 plus or minus 4.38 ng/ml; 2.85 plus or minus 2.3, 38.4 plus or minus 20.5, 6.0 plus or minus 6.6 mg/ml. Serum vitamin B-12 levels did not vary significantly over a 24-hour period although higher mean levels were observed at 1200 and 1800 hours, whereas the lowest mean levels were observed at 2400 and 0600 hours. Folacin activity varied significantly (P smaller than 0.01) over a 24-hour period with the mean level at 1800 hours significantly higher (P smaller than 0.01) than that at all other times. The overall means and standard deviations for vitamin B-12 and folacin, respectively, during this study were 742.2 plus or minus 785.6 pg/ml and 14.48 plus or minus 6.74 ng/ml. Serum levels of vitamin B-12 and folacin did not vary significantly between the follicular or luteal phases or show any significant correlation with the day of the menstrual cycle when analyzed by linear regression procedures. The overall means and standard deviations for vitamin B-12 and folacin, respectively, during the menstrual cycle study were 438.5 plus or minus 137.9 pg/ml and 14.8 plus or minus 4.27 ng/ml.