Metabolism of boar spermatozoa before, during preparation for, and after storage in liquid nitrogen

Boar spermatozoa incorporated more [14C]glycerol into lipid when incubated with 200 mM- than with 25 mM-glycerol. Measurements were made of the metabolism of spermatozoa while they were being prepared for frozen storage. [14C]-Glucose was converted to CO2 and lipid while the cells were cooling to 15 degrees C. Glycerol was added at 15 degrees C and during further cooling to 5 degrees C glucose metabolism was greatly reduced but [14C]glycerol was converted to CO2 and lipid. Under aerobic conditions spermatozoa accumulated lactate while cooling from 30 to 15 degrees C and from 15 to 5 degrees C. With essentially anaerobic conditions, although more lactate was accumulated this occurred only while the cells were cooling from 30 to 15 degrees C, and no further accumulation could be detected during cooling from 15 to 5 degrees C. When boar spermatozoa were incubated at 37 degrees C after storage in liquid nitrogen, metabolism of glycerol was greater than metabolism of glucose. It is suggested that this preferential use of glycerol during cooling and after storage may be one facet of its cryoprotective function. After storage, boar spermatozoa incorporated relatively less [14C]stearic and [14C]palmitic acids into phospholipids (especially phosphatidyl choline) than did freshly collected cells. Caffeine stimulated the oxygen uptake of freshly collected and thawed cells.