Serum progesterone, 17-hydroxyprogesterone and 17 B-oestradiol during the oestrous cycle in the swamp buffalo in Thailand

A radioimmunoassay for measuring serum progesterone (P), 17-hydroxyprogesterone (17-OHP) and 17-B-oestradio (E2) in buffaloes was described. One cm3 of pooled serum with three steroids added for recovery was extracted with ether and chromatographed on a celite microcolumn. The recovery of the standard P, 17-OHP and E2 was 72.9-89.6%, 77.0-97.0% and 85.5-101.3% respectively. The precision of within assay variance of these three steroids expressed as percentage of coefficient of variations was 8.2% (P and 17-OHP) and 8.3% (E2). The between assay variance was 13.2%(PT), 11.2% (17-OHP) and 12.9%(E2). The sensitivity of the assay varied between 3.5-25.0 pg. P, 4.0-25.0 pg 17-OHP and 2.5-10.0 g E2. Levels of serum progesterone, 17-hydroxyprogesterone and 17-B oestradiol were measured in the same serum samples at daily stages of the oestrous cycle in four female buffaloes; altogether there were 11 cycles. The swamp buffaloes have the normal oestrous cycles of 19-27 days. Progesterone levels in pre-oestrous-oestrous were 9.7 +-8.5 ng/100 cm3, the level beginning to rise by day 7 or 10, and reaching a peak of 38.8 +-12.2 ng/100 cm3 in 15.6 +-3.7 days of the cycle, then declining rapidly to the basal level about 4-7 days before the next oestrous cycle. The serum levels of 17-hydroxyprogesterone rose significantly in three peaks: preostrous-oestrous (21.3 +-8.3 ng/100 cm3), metoestrous (14.6+-6.6 ng/100 cm3) and dioestrous (20.2 +-8.1 ng/100 cm3). The average values in these three phases were 15.1+-7.1 ng/100 cm3, 9.7+-5.2 ng/100 cm3 and 10.6+-4.0 ng/100 cm3 respectively. The basal levels were below 5.0 ng/100 cm3. The oestradiol levels reached a peak on the day before oestrous. The average value of the peaks was 13.0+-4.0 ng/100 cm3. The duration of the peak was about four days, then it sharply declined to basal levels of 3.9+-1.0 ng/100 cm3.