Respiration rates and sugar utilization by marsupial spermatozoa

Abstract

Abstract This paper reports the first metabolic study of marsupial spermatozoa. The oxidative metabolism of the spermatozoa of the Australian brush‐tailed possum (Trichosurus vulpecula) was examined using a micro Warburg system. Semen was collected by electro‐ejaculation and washed twice in Ca 2+ free Krebs‐Ringer‐phosphate buffer containing antibiotics (KRPA). Washed spermatozoa suspended in fresh KRPA, were then incubated for 3 hours at 37° C in the presence and absence of added substrates (4 mM). The exogenous substrates tested were N‐acetylglucosamine, glucosamine, and glucose. Small quantities of radioactively labeled [ 14 C] substrates were included in the incubation media to allow measurement of substrate oxidation. Although the respiratory rate varied considerably between semen pools (replicate experiments), the relationship between total oxygen consumption (measured manometrically), and oxygen consumption accounted for by exogenous substrate utilization (calcuated from radioactivity recovered in the respiratory CO 2 ) was remarkably consistent. Oxidation of exogenous substrate accounted for 49–54% of the oxygen consumption, depending on the substrate used. There was, however, no evidence that addition of these substrates stimulated the respiratory rate over that found when no substrate was added. Lactate formation accounted for the greater part of exogenous substrate consumed.