Energy-rich phosphate compounds in bull semen: comparison of their metabolism with anaerobic heat production and impedance change frequency

Abstract

1. The concentrations of nucleotides and other energy rich phosphate compounds in bull spermatozoa and bull semen were examined at different times during anaerobic incubation at 37 degrees C. The variations in the concentrations of these compounds were compared with sperm heat production and impedance change frequency during anaerobic incubation. 2. Immediately after collection there were 129 $\pm $ 14 p$\mu $moles ATP, 120 $\pm $ 15$\cdot $5 p$\mu $moles ADP and 271 $\pm $ 22 p$\mu $moles AMP + HR (in approximately equal quantities) per spermatozoon. (10$^{3}$ p$\mu $moles $\times $ sperm density = $\mu $moles/ml. semen.) The correlation between ATP and ADP concentration per spermatozoon and the percentage of live spermatozoa in the sample was 0$\cdot $89, P < 0$\cdot $05. 3. During the whole period of incubation, which lasted 120 to 430 min, the following changes in sperm nucleotide content took place; (a) ATP decreased; (b) ADP decreased; (c) labile-P decreased; (d) AMP + HR increased; (e) there was no inverse relationship between ATP and ADP. 4. During the first hour of incubation, when there was a sharp fall in heat production and impedance change frequency, there was no comparable decline in ATP, ADP, or labile-P. In one experiment there was a 55% increase in ATP during this period. 5. Contrary to recent reports, compounds which were not nucleotides but which contained highly labile phosphate groups were found in bull semen. Their concentration was about 250 p$\mu $ moles/spermatozoon, of which 50 p$\mu $moles was creatine phosphate. The possibility that the rest was acetyl phosphate or 1,3-diphosphoglycerate is discussed. 6. When the anaerobic heat production of bull semen fell to zero, which in these experiments we established was not due to exhaustion of fructose in the external medium but to the low pH, $\leq $ 5$\cdot $5, of the seminal plasma, there were still significant amounts of nucleotides present in the spermatozoa.