Circadian variations of plasma LH and testosterone in adult swamp buffalo bulls.

Three swamp buffalo bulls aged 1.5, 1.10 and 2 years were submitted to frequent blood sampling every 15 m during a period of 25 h using an indwelling infusion set. Plasma LH and testosterone were quantified by radioimmunoassay technique. The levels of the two hormones in each individual exhibited episodic and nonrhythmic patterns. The number of LH peaks varied according to individual, ranging from no peak in one bull to 2 in the other two bulls. The mean LH concentrations during the period of study for each bull were 0.74, 0.33 and 1.17 ng/ml. Whereas the number of testosterone peaks varied between 1-10 and the average testosterone concentrations were 0.1, 0.33 and 0.55 ng/ml for the younger to the older bulls respectively. The testosterone peaks related to the LH peaks in each individual bull.