Isolation and enzymic properties of the midpiece of bull spermatozoa

摘要: Ejaculated bull spermatozoa were disrupted by sonic oscillation and fractionated differential centrifugation into a head, midpiece, tail fraction. The midpieces, which consist of mitochondria, showed well-preserved structure, practically free other cell components, as judging from electron micrographs. The isolated midpieces catalyzed the aerobic oxidation various substrates including Krebs-cycle intermediates, glycerol-1-phosphate, glutamate, β-hydroxybutyrate. Glycerol-1-phosphate was oxidized at relatively highest rate both in absence presence added cytochrome c, converted stoichiometrically dihydroxyacetone phosphate. Among pyruvate plus malate gave respiratory rate. addition however, greatly enhanced succinate, nearly up to with glycerol-1-phosphate but stimulated only slightly pyridine nucleotide-linked substrates. Adequate P:O ratios obtained most tested. stimulation succinate c caused decrease ratio. control indexes glutamate around 10, while those 2–4. The inhibited almost completely antimycin A, not rotenone amytal, whereas abolished all three inhibitors. 2,4-Dinitrophenol uncoupled respiration phosphorylation, oligomycin tightly-coupled accompanying phosphate uptake. For citrate isocitrate either NAD+ or NADP+ required. rates these further increased adding catalytic amount oxaloacetate. Externally NADH slowly midpiece fraction, strongly c. c-stimulated accompanied no phosphorylation. Indirect external way “glycerol-1-phosphate cycle” “β-hydroxybutyrate could be demonstrated. These features indicate that sperm mitochondria possess biochemical properties closely resembling tissues, spite their modified structure. The distribution some enzymes fragments has also been examined. Most glycolytic concentrated malic dehydrogenase located fraction. Anaerobic fructolysis produced minute fructose consumed lactate. demonstration glycerokinase activity homogenate suggests possible source is rapidly